HomeMy WebLinkAboutItem 6-WQMP - Preliminary_4th Submittal_2022-01-03- 1 -
Project Specific Water Quality Management Plan
A Template for Projects located within the Santa Ana Watershed Region of Riverside County
Project Title: 18 acre site at Mission Trail TTM 38378
Development No: Tentative Tract 38378
Design Review/Case No: PWQMP-2022-0005, Planning App#:2022-03 (Design Review#: 2022-02).
Original Date Prepared: March 4, 2022
Revision Date(s):
Prepared for Compliance with
Regional Board Order No. R8-2010-0033
Contact Information:
Prepared for: The Development at
Mission Trails - Lake Elsinore, LLC
1020 2nd Street
Encinitas, CA 92024
Brett Crowder, Project Manager
(949) 632-3122
Prepared by: Wilson Mikami Corporation
9 Corporate Park, Suite 100
Irvine, CA 92606
Scott M. Wilson, PE, PLS, Principal
(949) 679-0090
Preliminary
Final
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A Brief Introduction
This Project-Specific WQMP Template for the Santa Ana Region has been prepared to help guide you in
documenting compliance for your project. Because this document has been designed to specifically
document compliance, you will need to utilize the WQMP Guidance Document as your “how-to” manual
to help guide you through this process. Both the Template and Guidance Document go hand-in-hand, and
will help facilitate a well prepared Project-Specific WQMP. Below is a flowchart for the layout of this
Template that will provide the steps required to document compliance.
Section A
Project and Site Information
Section B
Optimize Site Utilization
Section C
Delineate Drainage Management Areas (DMAs)
Section G
Source Control BMPs
Section I
Operation, Maintenance, and Funding
Section F
Hydromodification
Section E
Alternative Compliance
Section D
Implement LID BMPs
Section H
Construction Plan Checklist
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OWNER’S CERTIFICATION
This Project-Specific Water Quality Management Plan (WQMP) has been prepared for The Development at Mission
Trails - Lake Elsinore, LLC by Wilson Mikami Corporation for The 18 acre site at Mission Trail TTM 38378 project.
This WQMP is intended to comply with the requirements of City of Lake Elsinore Grading Ordinance which includes
the requirement for the preparation and implementation of a Project-Specific WQMP.
The undersigned, while owning the property/project described in the preceding paragraph, shall be responsible for
the implementation and funding of this WQMP and will ensure that this WQMP is amended as appropriate to reflect
up-to-date conditions on the site. In addition, the property owner accepts responsibility for interim operation and
maintenance of Stormwater BMPs until such time as this responsibility is formally transferred to a subsequent
owner. This WQMP will be reviewed with the facility operator, facility supervisors, employees, tenants, maintenance
and service contractors, or any other party (or parties) having responsibility for implementing portions of this
WQMP. At least one copy of this WQMP will be maintained at the project site or project office in perpetuity. The
undersigned is authorized to certify and to approve implementation of this WQMP. The undersigned is aware that
implementation of this WQMP is enforceable under City of Lake Elsinore Water Quality Ordinance (Municipal Code
Chapter 14.08).
"I, the undersigned, certify under penalty of law that the provisions of this WQMP have been reviewed and accepted
and that the WQMP will be transferred to future successors in interest."
Owner’s Signature Date
Owner’s Printed Name Owner’s Title/Position
PREPARER’S CERTIFICATION
“The selection, sizing and design of stormwater treatment and other stormwater quality and quantity control
measures in this plan meet the requirements of Regional Water Quality Control Board Order No. R8-2010-0033 and
any subsequent amendments thereto.”
Preparer’s Signature Date
Scott M. Wilson Principal
Preparer’s Printed Name Preparer’s Title/Position
Preparer’s Licensure: RCE 49884
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Table of Contents
Section A: Project and Site Information........................................................................................................ 6
A.1 Maps and Site Plans ............................................................................................................................ 6
A.2 Identify Receiving Waters ................................................................................................................... 7
A.3 Additional Permits/Approvals required for the Project: .................................................................... 7
Section B: Optimize Site Utilization (LID Principles) ..................................................................................... 8
Section C: Delineate Drainage Management Areas (DMAs) ......................................................................... 9
Section D: Implement LID BMPs ................................................................................................................. 10
D.1 Infiltration Applicability .................................................................................................................... 10
D.2 Harvest and Use Assessment ............................................................................................................ 11
D.3 Bioretention and Biotreatment Assessment .................................................................................... 13
D.4 Feasibility Assessment Summaries ................................................................................................... 14
D.5 LID BMP Sizing .................................................................................................................................. 15
Section E: Alternative Compliance (LID Waiver Program) .......................................................................... 16
E.1 Identify Pollutants of Concern .......................................................................................................... 17
E.2 Stormwater Credits ........................................................................................................................... 18
E.3 Sizing Criteria ..................................................................................................................................... 18
E.4 Treatment Control BMP Selection .................................................................................................... 19
Section F: Hydromodification ..................................................................................................................... 20
F.1 Hydrologic Conditions of Concern (HCOC) Analysis .......................................................................... 20
F.2 HCOC Mitigation ................................................................................................................................ 21
Section G: Source Control BMPs ................................................................................................................. 22
Section H: Construction Plan Checklist ....................................................................................................... 25
Section I: Operation, Maintenance and Funding ........................................................................................ 26
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List of Tables
Table A.1 Identification of Receiving Waters ................................................................................................ 7
Table A.2 Other Applicable Permits .............................................................................................................. 7
Table C.1 DMA Classifications ....................................................................................................................... 9
Table C.2 Type ‘A’, Self-Treating Areas ......................................................................................................... 9
Table C.3 Type ‘B’, Self-Retaining Areas ....................................................................................................... 9
Table C.4 Type ‘C’, Areas that Drain to Self-Retaining Areas ........................................................................ 9
Table C.5 Type ‘D’, Areas Draining to BMPs ............................................................................................... 10
Table D.1 Infiltration Feasibility .................................................................................................................. 10
Table D.2 LID Prioritization Summary Matrix ............................................................................................. 14
Table D.3 DCV Calculations for LID BMPs ...................................................... Error! Bookmark not defined.
Table E.1 Potential Pollutants by Land Use Type ........................................................................................ 17
Table E.2 Water Quality Credits .................................................................................................................. 18
Table E.3 Treatment Control BMP Sizing ....................................................... Error! Bookmark not defined.
Table E.4 Treatment Control BMP Selection .............................................................................................. 19
Table F.1 Hydrologic Conditions of Concern Summary .............................................................................. 20
Table G.1 Permanent and Operational Source Control Measures ............................................................. 22
Table H.1 Construction Plan Cross-reference ............................................................................................. 25
List of Appendices
Appendix 1: Maps and Site Plans ................................................................................................................ 27
Appendix 2: Construction Plans .................................................................................................................. 28
Appendix 3: Soils Information ..................................................................................................................... 29
Appendix 4: Historical Site Conditions ........................................................................................................ 30
Appendix 5: LID Infeasibility ........................................................................................................................ 31
Appendix 6: BMP Design Details ................................................................................................................. 33
Appendix 7: Hydromodification .................................................................................................................. 35
Appendix 8: Source Control ........................................................................................................................ 36
Appendix 9: O&M ....................................................................................................................................... 37
Appendix 10: Educational Materials ....................................................................................................... - 38 -
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Section A: Project and Site Information
PROJECT INFORMATION
Type of Project: Mixed Use: Single Family Residential
Planning Area: East Lake Specific Plan
Community Name: East Lake Specific Plan
Development Name: Tentative Tract 38378, 18 Acre Site at Mission Trail
PROJECT LOCATION
Latitude & Longitude (DMS): 33°38'3"N, 117°17'28"W (33.634167, 117.291111)
Project Watershed and Sub-Watershed: Santa Ana River Watershed and San Jacinto River Sub-Watershed
APN(s): 370-050-019, 020 and 032
Map Book and Page No.: Map Book 543, Pages 259
PROJECT CHARACTERISTICS
Proposed or Potential Land Use(s) Singled Family Residential
Proposed or Potential SIC Code(s) 1522
Area of Impervious Project Footprint (SF) 788,192 SF
Total Area of proposed Impervious Surfaces within the Project Limits (SF)/or Replacement 507,769 SF
Does the project consist of offsite road improvements? Y N
Does the project propose to construct unpaved roads? Y N
Is the project part of a larger common plan of development (phased project)? Y N
EXISTING SITE CHARACTERISTICS
Total area of existing Impervious Surfaces within the project limits (SF) 0
Is the project located within any MSHCP Criteria Cell? Y N
If so, identify the Cell number:
Are there any natural hydrologic features on the project site? Y N
Is a Geotechnical Report attached? Y N
If no Geotech. Report, list the NRCS soils type(s) present on the site (A, B, C and/or D): See Appendix 3
What is the Water Quality Design Storm Depth for the project? 0.80 in
A.1 Maps and Site Plans
When completing your Project-Specific WQMP, include a map of the local vicinity and existing site. In
addition, include all grading, drainage, landscape/plant palette and other pertinent construction plans in
Appendix 2. At a minimum, your WQMP Site Plan should include the following:
• Drainage Management Areas
• Proposed Structural BMPs
• Drainage Path
• Drainage Infrastructure, Inlets, Overflows
• Source Control BMPs
• Buildings, Roof Lines, Downspouts
• Impervious Surfaces
• Standard Labeling
Use your discretion on whether or not you may need to create multiple sheets or can appropriately
accommodate these features on one or two sheets. Keep in mind that the Co-Permittee plan reviewer
must be able to easily analyze your project utilizing this template and its associated site plans and maps.
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The project site currently is a vacant site with little ground cover and no current uses for the site. The
proposed project is duplex condominium homes with a total on-site project area of 9.72 acres. The total
impervious area is 6.97 acres and pervious area is 2.75 acres.
A.2 Identify Receiving Waters
Using Table A.1 below, list in order of upstream to downstream, the receiving waters that the project site
is tributary to. Continue to fill each row with the Receiving Water’s 303(d) listed impairments (if any),
designated beneficial uses, and proximity, if any, to a RARE beneficial use. Include a map of the receiving
waters in Appendix 1.
Table A.1 Identification of Receiving Waters
Receiving Waters EPA Approved 303(d) List
Impairments
Designated
Beneficial Uses
Proximity to RARE
Beneficial Use
Lake Elsinore Nutrients
Organic Enrichment/Low Dissolved Oxygen
PCBs (Polychlorinated biphenyls)
Unknown Toxicity
MUN, AGR, GWR,
REC1, REC2, COLD,
WILD
N/A
A.3 Additional Permits/Approvals required for the Project:
Table A.2 Other Applicable Permits
Agency Permit Required
State Department of Fish and Game, 1602 Streambed Alteration Agreement Y N
State Water Resources Control Board, Clean Water Act (CWA) Section 401 Water Quality Cert. Y N
US Army Corps of Engineers, CWA Section 404 Permit Y N
US Fish and Wildlife, Endangered Species Act Section 7 Biological Opinion Y N
Statewide Construction General Permit Coverage Y N
Statewide Industrial General Permit Coverage Y N
Western Riverside MSHCP Consistency Approval (e.g., JPR, DBESP) Y N
Other (please list in the space below as required)
City Building and Grading Permit Y N
If yes is answered to any of the questions above, the Co-Permittee may require proof of
approval/coverage from those agencies as applicable including documentation of any associated
requirements that may affect this Project-Specific WQMP.
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Section B: Optimize Site Utilization (LID Principles)
Site Optimization
The following questions are based upon Section 3.2 of the WQMP Guidance Document. Review of the
WQMP Guidance Document will help you determine how best to optimize your site and subsequently
identify opportunities and/or constraints, and document compliance.
Did you identify and preserve existing drainage patterns? If so, how? If not, why?
The site layout conforms to natural landform, which drains from east to west direction.
Did you identify and protect existing vegetation? If so, how? If not, why?
N/A, no significant trees and other natural vegetation to preserve.
Did you identify and preserve natural infiltration capacity? If so, how? If not, why?
N/A, Infiltration BMPs are not to be used for this site per Section D.1
Did you identify and minimize impervious area? If so, how? If not, why?
Landscape areas are proposed where possible to minimize impervious areas.
Did you identify and disperse runoff to adjacent pervious areas? If so, how? If not, why?
Stormwater is proposed to be intercepted in inlets in designated landscaped areas and discharged into
bioretention/biofiltration treatment Filterra Units and then discharged into the existing four corner storm
drain system which ultimately discharges directly to Lake Elsinore back basin.
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Section C: Delineate Drainage Management Areas
(DMAs)
Table C.1 DMA Classifications
DMA Name or ID Surface Type(s)1 Area (Sq. Ft.) DMA Type
A Roofs, Asphalt, and Landscaping 103,080 Type D
B Roofs, Asphalt, and Landscaping 56,857 Type D
C Roofs, Asphalt, and Landscaping 106,359 Type D
D Roofs, Asphalt, and Landscaping 76,075 Type D
E Roofs, Asphalt, and Landscaping 76,789 Type D
F Roofs, Asphalt, and Landscaping 100,711 Type D
G Roofs, Asphalt, and Landscaping 45,891 Type D
H Roofs, Asphalt, and Landscaping 51,632 Type D
I Roofs, Asphalt, and Landscaping 62,238 Type D
J Roofs, Asphalt, and Landscaping 43,485 Type D
K Asphalt and Landscaping 38,145 Type D
1Reference Table 2-1 in the WQMP Guidance Document to populate this column
Table C.2 Type ‘A’, Self-Treating Areas
DMA Name or ID Area (Sq. Ft.) Stabilization Type Irrigation Type (if any)
N/A
Table C.3 Type ‘B’, Self-Retaining Areas
Self-Retaining Area
Type ‘C’ DMAs that are draining to the Self-Retaining
Area
DMA
Name/
ID
Post-project
surface type
Area
(square
feet)
Storm
Depth
(inches) DMA Name /
ID
[C] from Table C.4 =
Required Retention Depth
(inches)
[A] [B] [C] [D]
N/A [𝐷𝐷]=[𝐵𝐵]+[𝐵𝐵]∙[𝐶𝐶][𝐴𝐴]
Table C.4 Type ‘C’, Areas that Drain to Self-Retaining Areas
DMA Receiving Self-Retaining DMA DMA Name/ ID Area (square feet) Post-project surface type Runoff factor Product
DMA name /ID
Area (square
feet) Ratio
[A] [B] [C] = [A] x [B] [D] [C]/[D]
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Table C.5 Type ‘D’, Areas Draining to BMPs
DMA Name or ID BMP Name or ID
A Bioretention/BioFiltration BMP Filterra Model FTBSV0610
B Bioretention/BioFiltration BMP Filterra Model FTBSV0608
C Bioretention/BioFiltration BMP Filterra Model FTBSV0608
D Bioretention/BioFiltration BMP Filterra Model FTIBC0610-C
E Bioretention/BioFiltration BMP Filterra Model FTIBC 0610-C
F Bioretention/BioFiltration BMP Filterra Model FTBSV0612
G Bioretention/BioFiltration BMP Filterra Model FTBSV0606
H Bioretention/BioFiltration BMP Filterra Model FTBSV0606
I Bioretention/BioFiltration BMP Filterra Model FTBSV0608
J Bioretention/BioFiltration BMP Filterra Model FTBSV0606
K Bioretention/BioFiltration BMP Filterra Model FTBSV0606
Note: More than one drainage management area can drain to a single LID BMP, however, one drainage
management area may not drain to more than one BMP.
Section D: Implement LID BMPs
D.1 Infiltration Applicability
Is there an approved downstream ‘Highest and Best Use’ for stormwater runoff (see discussion in Chapter
2.4.4 of the WQMP Guidance Document for further details)? Y N Lake Elsinore
If yes has been checked, Infiltration BMPs shall not be used for the site. If no, continue working through
this section to implement your LID BMPs. It is recommended that you contact your Co-Permittee to verify
whether or not your project discharges to an approved downstream ‘Highest and Best Use’ feature.
Geotechnical Report
Is this project classified as a small project consistent with the requirements of Chapter 2 of the WQMP
Guidance Document? Y N
Infiltration Feasibility
Table D.1 Infiltration Feasibility
Does the project site… YES NO
…have any DMAs with a seasonal high groundwater mark shallower than 10 feet? X
If Yes, list affected DMAs:
…have any DMAs located within 100 feet of a water supply well? X
If Yes, list affected DMAs:
…have any areas identified by the geotechnical report as posing a public safety risk where infiltration of stormwater
could have a negative impact?
X
If Yes, list affected DMAs:
…have measured in-situ infiltration rates of less than 1.6 inches / hour? Has not been studied yet. X
If Yes, list affected DMAs:
…have significant cut and/or fill conditions that would preclude in-situ testing of infiltration rates at the final
infiltration surface?
X
If Yes, list affected DMAs:
…geotechnical report identify other site-specific factors that would preclude effective and safe infiltration? X
Describe here:
If you answered “Yes” to any of the questions above for any DMA, Infiltration BMPs should not be used
for those DMAs and you should proceed to the assessment for Harvest and Use below.
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D.2 Harvest and Use Assessment (N/A)
Please check what applies:
Reclaimed water will be used for the non-potable water demands for the project.
Downstream water rights may be impacted by Harvest and Use as approved by the Regional
Board (verify with the Copermittee).
The Design Capture Volume will be addressed using Infiltration Only BMPs. In such a case,
Harvest and Use BMPs are still encouraged, but it would not be required if the Design Capture
Volume will be infiltrated or evapotranspired.
If any of the above boxes have been checked, Harvest and Use BMPs need not be assessed for the site. If
neither of the above criteria applies, follow the steps below to assess the feasibility of irrigation use, toilet
use and other non-potable uses (e.g., industrial use).
Irrigation Use Feasibility
Complete the following steps to determine the feasibility of harvesting stormwater runoff for Irrigation
Use BMPs on your site:
Step 1: Identify the total area of irrigated landscape on the site, and the type of landscaping used.
Total Area of Irrigated Landscape: 280,423 SF
Type of Landscaping (Conservation Design or Active Turf): Active Turf
Step 2: Identify the planned total of all impervious areas on the proposed project from which runoff
might be feasibly captured and stored for irrigation use. Depending on the configuration of
buildings and other impervious areas on the site, you may consider the site as a whole, or parts
of the site, to evaluate reasonable scenarios for capturing and storing runoff and directing the
stored runoff to the potential use(s) identified in Step 1 above.
Total Area of Impervious Surfaces: 507,769 SF
Step 3: Cross reference the Design Storm depth for the project site (see Exhibit A of the WQMP
Guidance Document) with the left column of Table 2-3 in Chapter 2 to determine the minimum
area of Effective Irrigated Area per Tributary Impervious Area (EIATIA).
Enter your EIATIA factor: 0.98
Step 4: Multiply the unit value obtained from Step 3 by the total of impervious areas from Step 2 to
develop the minimum irrigated area that would be required.
Minimum required irrigated area: 497,614 SF
Step 5: Determine if harvesting stormwater runoff for irrigation use is feasible for the project by
comparing the total area of irrigated landscape (Step 1) to the minimum required irrigated area
(Step 4).
Minimum required irrigated area (Step 4) Available Irrigated Landscape (Step 1)
497,614 SF 280,423 SF
Conclusion: harvesting stormwater for irrigation use is not feasible.
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Toilet Use Feasibility
Complete the following steps to determine the feasibility of harvesting stormwater runoff for toilet
flushing uses on your site:
Step 1: Identify the projected total number of daily toilet users during the wet season, and account for
any periodic shut downs or other lapses in occupancy:
Projected Number of Daily Toilet Users: 478
Project Type: Single Family Residential
Step 2: Identify the planned total of all impervious areas on the proposed project from which runoff
might be feasibly captured and stored for toilet use. Depending on the configuration of
buildings and other impervious areas on the site, you may consider the site as a whole, or parts
of the site, to evaluate reasonable scenarios for capturing and storing runoff and directing the
stored runoff to the potential use(s) identified in Step 1 above.
Total Area of Impervious Surfaces: 507,769 SF
Step 3: Enter the Design Storm depth for the project site (see Exhibit A) into the left column of Table 2-
1 in Chapter 2 to determine the minimum number or toilet users per tributary impervious acre
(TUTIA).
Enter your TUTIA factor: 131 tu/acre
Step 4: Multiply the unit value obtained from Step 3 by the total of impervious areas from Step 2 to
develop the minimum number of toilet users that would be required.
Minimum number of toilet users: 1,527
Step 5: Determine if harvesting stormwater runoff for toilet flushing use is feasible for the project by
comparing the Number of Daily Toilet Users (Step 1) to the minimum required number of toilet
users (Step 4).
Minimum required Toilet Users (Step 4) Projected number of toilet users (Step 1)
1,527 478
Conclusion: harvesting stormwater for toilet flushing use is not feasible.
Other Non-Potable Use Feasibility (N/A)
Are there other non-potable uses for stormwater runoff on the site (e.g. industrial use)? See Chapter 2 of
the Guidance for further information. If yes, describe below. If no, write N/A.
N/A
Step 1: Identify the projected average daily non-potable demand, in gallons per day, during the wet
season and accounting for any periodic shut downs or other lapses in occupancy or operation.
Average Daily Demand:
Step 2: Identify the planned total of all impervious areas on the proposed project from which runoff
might be feasibly captured and stored for the identified non-potable use. Depending on the
configuration of buildings and other impervious areas on the site, you may consider the site as
a whole, or parts of the site, to evaluate reasonable scenarios for capturing and storing runoff
and directing the stored runoff to the potential use(s) identified in Step 1 above.
Total Area of Impervious Surfaces:
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Step 3: Enter the Design Storm depth for the project site (see Exhibit A) into the left column of Table 2-
3 in Chapter 2 to determine the minimum demand for non-potable uses per tributary
impervious acre.
Enter the factor from Table 2-3:
Step 4: Multiply the unit value obtained from Step 4 by the total of impervious areas from Step 3 to
develop the minimum number of gallons per day of non-potable use that would be required.
Minimum required use:
Step 5: Determine if harvesting stormwater runoff for other non-potable use is feasible for the project
by comparing the Number of Daily Toilet Users (Step 1) to the minimum required number of
toilet users (Step 4).
Minimum required non-potable use (Step 4) Projected average daily use (Step 1)
If Irrigation, Toilet and Other Use feasibility anticipated demands are less than the applicable minimum
values, Harvest and Use BMPs are not required and you should proceed to utilize LID Bioretention and
Biotreatment, unless a site-specific analysis has been completed that demonstrates technical infeasibility
as noted in D.3 below.
D.3 Bioretention and Biotreatment Assessment
Other LID Bioretention and Biotreatment BMPs as described in Chapter 2.4.7 of the WQMP Guidance
Document are feasible on nearly all development sites with sufficient advance planning.
Select one of the following:
LID Bioretention/Biotreatment BMPs will be used for some or all DMAs of the project as noted
below in Section D.4 (note the requirements of Section 3.4.2 in the WQMP Guidance
Document).
A site-specific analysis demonstrating the technical infeasibility of all LID BMPs has been
performed and is included in Appendix 5. If you plan to submit an analysis demonstrating the
technical infeasibility of LID BMPs, request a pre-submittal meeting with the Copermittee to
discuss this option. Proceed to Section E to document your alternative compliance measures.
Note: LID Bioretention BMPs are feasible, however, due to constraints in the depth of the existing outlet
storm drain and the project design as documented in Appendix 5, a Filterra Bioretention/Biofiltration
System BMP will be used for all DMAs of the project. However, the Permittee has not approved the
Filterra Bioretention/Biofiltration System BMP product as a LID BMP so it is considered herein as
Treatment Control, Alternative Compliance.
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D.4 Feasibility Assessment Summaries
From the Infiltration, Harvest and Use, Bioretention and Biotreatment Sections above, complete Table
D.2 below to summarize which LID BMPs are technically feasible, and which are not, based upon the
established hierarchy.
Table D.2 LID Prioritization Summary Matrix
DMA
Name/ID
LID BMP Hierarchy No LID
(Alternative
Compliance) 1. Infiltration 2. Harvest and use 3. Bioretention 4. Biotreatment
A
B
C
D
E
F
G
H
I
J
K
For those DMAs where LID BMPs are not feasible, provide a brief narrative below summarizing why they
are not feasible, include your technical infeasibility criteria in Appendix 5, and proceed to Section E below
to document Alternative Compliance measures for those DMAs. Recall that each proposed DMA must
pass through the LID BMP hierarchy before alternative compliance measures may be considered.
LID Bioretention BMPs are feasible, however, due to constraints in the depth of the existing outlet storm
drain and project design as documented in Appendix 5, a Filterra Bioretention/Biofiltration System BMP
will be used for all DMAs of the project. However, the Permittee has not approved the Filterra
Bioretention/Filtration System BMP product as a LID BMP so it is considered herein as Treatment Control,
Alternative Compliance.
The project discharges to Lake Elsinore which has an approved downstream ‘Highest and Best Use’ for
storm water runoff per the WQMP Guidance documents. As a result, no infiltration BMPs are proposed
for the project.
DMA A-K – A Filterra Bioretention/Biofiltration System BMP Unit will be installed to treat street/hardscape
and landscape runoff within the site prior to discharging the flow off-site. This project discharges to
approved downstream ‘Highest and Best Use’ for stormwater runoff, Lake Elsinore.
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D.5 LID BMP Sizing
Each LID BMP must be designed to ensure that the Design Capture Volume will be addressed by the
selected BMPs. First, calculate the Design Capture Volume for each LID BMP using the VBMP worksheet in
Appendix F of the LID BMP Design Handbook. Second, design the LID BMP to meet the required VBMP using
a method approved by the Copermittee. Utilize the worksheets found in the LID BMP Design Handbook
or consult with your Copermittee to assist you in correctly sizing your LID BMPs. Complete Table D.3 below
to document the Design Capture Volume and the Proposed Volume for each LID BMP. Provide the
completed design procedure sheets for each LID BMP in Appendix 6. You may add additional rows to the
table below as needed.
The project discharges to Lake Elsinore which has an approved downstream ‘Highest and Best Use’ for
storm water runoff per the WQMP Guidance documents. As a result, an infiltration/volume based BMP
is not used. In addition, an Alternative Compliance BMP (Filterra Bioretention/Biofiltration) is proposed
the project. This BMP is flow based BMP sizing.
Table D.3 Calculations for LID BMPs
DMA
Type/ID
DMA
Area
(square
feet)
Post-
Project
Surface
Type
Effective
Impervious
Fraction, If
DMA
Runoff
Factor
DMA
Areas x
Runoff
Factor
[A] [B] [C] [A] x [C]
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate, QBMP
(cubic feet per
second)
Proposed
Flow Rate
on Plans
(cubic
feet per
second)
[G]
[B], [C] is obtained as described in Section 2.3.1 of the WQMP Guidance Document
[E] is obtained from Exhibit A in the WQMP Guidance Document
[G] is obtained from a design procedure sheet, such as in LID BMP Design Handbook and placed in Appendix 6. The project
discharges to Lake Elsinore which has an approved downstream ‘Highest and Best Use’ for storm water runoff per the WQMP
Guidance documents. As a result, no infiltration LID BMPs are proposed for the project. A flow based BMP is proposed for the
project.
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Section E: Alternative Compliance (LID Waiver Program)
LID BMPs are expected to be feasible on virtually all projects. Where LID BMPs have been demonstrated
to be infeasible as documented in Section D, other Treatment Control BMPs must be used (subject to LID
waiver approval by the Co-permittee). Check one of the following Boxes:
LID Principles and LID BMPs have been incorporated into the site design to fully address all
Drainage Management Areas. No alternative compliance measures are required for this project
and thus this Section is not required to be completed.
- Or -
The following Drainage Management Areas are unable to be addressed using LID BMPs. A site-
specific analysis demonstrating technical infeasibility of LID BMPs has been approved by the
Co-Permittee and included in Appendix 5. Additionally, no downstream regional and/or sub-
regional LID BMPs exist or are available for use by the project. The following alternative
compliance measures on the following pages are being implemented to ensure that any pollutant
loads expected to be discharged by not incorporating LID BMPs, are fully mitigated.
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E.1 Identify Pollutants of Concern
Utilizing Table A.1 from Section A above which noted your project’s receiving waters and their associated
EPA approved 303(d) listed impairments, cross reference this information with that of your selected
Priority Development Project Category in Table E.1 below. If the identified General Pollutant Categories
are the same as those listed for your receiving waters, then these will be your Pollutants of Concern and
the appropriate box or boxes will be checked on the last row. The purpose of this is to document
compliance and to help you appropriately plan for mitigating your Pollutants of Concern in lieu of
implementing LID BMPs.
Table E.1 Potential Pollutants by Land Use Type
Priority Development
Project Categories and/or Project Features (check those that apply)
General Pollutant Categories
Bacterial Indicators Metals Nutrients Pesticides Toxic Organic Compounds Sediments Trash & Debris Oil & Grease
Detached Residential
Development P N P P N P P P
Attached Residential
Development P N P P N P P P(2)
Commercial/Industrial
Development P(3) P P(1) P(1) P(5) P(1) P P
Automotive Repair
Shops N P N N P(4, 5) N P P
Restaurants
(>5,000 ft2) P N N N N N P P
Hillside Development
(>5,000 ft2) P N P P N P P P
Parking Lots
(>5,000 ft2) P(6) P P(1) P(1) P(4) P(1) P P
Retail Gasoline Outlets N P N N P N P P
Project Priority Pollutant(s)
of Concern
P = Potential
N = Not Potential
(1) A potential Pollutant if non-native landscaping exists or is proposed onsite; otherwise not expected
(2) A potential Pollutant if the project includes uncovered parking areas; otherwise not expected
(3) A potential Pollutant is land use involving animal waste
(4) Specifically petroleum hydrocarbons
(5) Specifically solvents
(6) Bacterial indicators are routinely detected in pavement runoff
- 18 -
E.2 Stormwater Credits
Projects that cannot implement LID BMPs but nevertheless implement smart growth principles are
potentially eligible for Stormwater Credits. Utilize Table 3-8 within the WQMP Guidance Document to
identify your Project Category and its associated Water Quality Credit. If not applicable, write N/A.
Table E.2 Water Quality Credits
Qualifying Project Categories Credit Percentage2
N/A
Total Credit Percentage1
1Cannot Exceed 50%
2Obtain corresponding data from Table 3-8 in the WQMP Guidance Document
E.3 Sizing Criteria
After you appropriately considered Stormwater Credits for your project, utilize Table E.3 below to
appropriately size them to the DCV, or Design Flow Rate, as applicable. Please reference Chapter 3.5.2 of
the WQMP Guidance Document for further information.
Table E.3 Treatment Control BMP Sizing
DMA
Type/ID
DMA
Area
(square
feet)
Post-
Project
Surface
Type
Effective
Impervious
Fraction, If
DMA
Runoff
Factor
DMA
Areas x
Runoff
Factor
Filterra Bioretention/Biofiltration
System
[A] [B] [C] [A] x [C]
A 103,080 Mixed 0.704 0.50 51,301
Design
Storm
Depth
(in)
Minimum
Design Flow
Rate (cubic feet
or cfs)
Proposed
Flow Rate
on Plans
(cubic
feet per
second)
[G]
B 56,857 Mixed 0.769 0.56 32,075
C 106,359 Mixed 0.585 0.40 42,291
D 76,075 Mixed 0.814 0.62 46,860
E 76,789 Mixed 0.807 0.61 46,655
F 100,711 Mixed 0.763 0.56 56,115
G 45,891 Mixed 0.750 0.54 24,952
H 51,632 Mixed 0.735 0.53 27,272
I 62,238 Mixed 0.724 0.52 32,185
J 43,485 Mixed 0.778 0.57 24,964
K 38,145 Mixed 0.875 0.69 26,505
761,262 411175 0.80 1.89 2.0
[B], [C] is obtained as described in Section 2.3.1 from the WQMP Guidance Document
[E] is obtained from Exhibit A in the WQMP Guidance Document
[G] is for Flow-Based Treatment Control BMPs [G] = 43,560, for Volume-Based Control Treatment BMPs, [G] = 12
[H] is from the Total Credit Percentage as Calculated from Table E.2 above
[I] as obtained from a design procedure sheet from the BMP manufacturer and should be included in Appendix 6
- 19 -
E.4 Treatment Control BMP Selection
Treatment Control BMPs typically provide proprietary treatment mechanisms to treat potential pollutants
in runoff, but do not sustain significant biological processes. Treatment Control BMPs must have a removal
efficiency of a medium or high effectiveness as quantified below:
• High: equal to or greater than 80% removal efficiency
• Medium: between 40% and 80% removal efficiency
Such removal efficiency documentation (e.g., studies, reports, etc.) as further discussed in Chapter 3.5.2
of the WQMP Guidance Document, must be included in Appendix 6. In addition, ensure that proposed
Treatment Control BMPs are properly identified on the WQMP Site Plan in Appendix 1.
Table E.4 Treatment Control BMP Selection
Selected Treatment Control BMP
Name or ID1
Priority Pollutant(s) of
Concern to Mitigate2
Removal Efficiency
Percentage3
Filterra Units (DMA A-K)
Bioretention/Biofiltration BMP
(See Filterra Equivalence Analysis in
Appendix 6)
Bacterial Indicators,
Nutrients, Pesticides,
Sediments, Trash and Debris,
Oil and Grease
High removal efficiency
1 Treatment Control BMPs must not be constructed within Receiving Waters. In addition, a proposed Treatment Control BMP may be
listed more than once if they possess more than one qualifying pollutant removal efficiency.
2 Cross Reference Table E.1 above to populate this column.
3 As documented in a Co-Permittee Approved Study and provided in Appendix 6.
- 20 -
Section F: Hydromodification
F.1 Hydrologic Conditions of Concern (HCOC) Analysis
Once you have determined that the LID design is adequate to address water quality requirements, you
will need to assess if the proposed LID Design may still create a HCOC. Review Chapters 2 and 3 (including
Figure 3-7) of the WQMP Guidance Document to determine if your project must mitigate for
Hydromodification impacts. If your project meets one of the following criteria which will be indicated by
the check boxes below, you do not need to address Hydromodification at this time. However, if the
project does not qualify for Exemptions 1, 2 or 3, then additional measures must be added to the design
to comply with HCOC criteria. This is discussed in further detail below in Section F.2.
HCOC EXEMPTION 1: The Priority Development Project disturbs less than one acre. The Copermittee
has the discretion to require a Project-Specific WQMP to address HCOCs on projects less than one
acre on a case by case basis. The disturbed area calculation should include all disturbances associated
with larger common plans of development.
Does the project qualify for this HCOC Exemption? Y N
If Yes, HCOC criteria do not apply.
HCOC EXEMPTION 2: The volume and time of concentration1 of storm water runoff for the post-
development condition is not significantly different from the pre-development condition for a 2-year
return frequency storm (a difference of 5% or less is considered insignificant) using one of the
following methods to calculate:
• Riverside County Hydrology Manual
• Technical Release 55 (TR-55): Urban Hydrology for Small Watersheds (NRCS 1986), or
derivatives thereof, such as the Santa Barbara Urban Hydrograph Method
• Other methods acceptable to the Co-Permittee
Does the project qualify for this HCOC Exemption? Y N
If Yes, report results in Table F.1 below and provide your substantiated hydrologic analysis in
Appendix 7.
Table F.1 Hydrologic Conditions of Concern Summary
2 year – 24 hour
Pre-condition Post-condition % Difference
Time of
Concentration
Volume (Cubic Feet)
1 Time of concentration is defined as the time after the beginning of the rainfall when all portions of the drainage basin
are contributing to flow at the outlet.
- 21 -
HCOC EXEMPTION 3: All downstream conveyance channels to an adequate sump (for example,
Prado Dam, Lake Elsinore, Canyon Lake, Santa Ana River, or other lake, reservoir or naturally
erosion resistant feature) that will receive runoff from the project are engineered and regularly
maintained to ensure design flow capacity; no sensitive stream habitat areas will be adversely
affected; or are not identified on the Co-Permittees Hydromodification Sensitivity Maps.
Does the project qualify for this HCOC Exemption? Y N
If Yes, HCOC criteria do not apply and note below which adequate sump applies to this HCOC
qualifier:
Downstream conveyance channels directly into Lake Elsinore which is engineered and regularly
maintained to ensure design flow capacity.
F.2 HCOC Mitigation
If none of the above HCOC Exemption Criteria are applicable, HCOC criteria is considered mitigated if they
meet one of the following conditions:
a. Additional LID BMPS are implemented onsite or offsite to mitigate potential erosion or habitat
impacts as a result of HCOCs. This can be conducted by an evaluation of site-specific conditions
utilizing accepted professional methodologies published by entities such as the California
Stormwater Quality Association (CASQA), the Southern California Coastal Water Research Project
(SCCRWP), or other Co-Permittee approved methodologies for site-specific HCOC analysis.
b. The project is developed consistent with an approved Watershed Action Plan that addresses
HCOC in Receiving Waters.
c. Mimicking the pre-development hydrograph with the post-development hydrograph, for a 2-year
return frequency storm. Generally, the hydrologic conditions of concern are not significant, if the
post-development hydrograph is no more than 10% greater than pre-development hydrograph.
In cases where excess volume cannot be infiltrated or captured and reused, discharge from the
site must be limited to a flow rate no greater than 110% of the pre-development 2-year peak flow.
Be sure to include all pertinent documentation used in your analysis of the items a, b or c in Appendix 7.
- 22 -
Section G: Source Control BMPs
Source control BMPs include permanent, structural features that may be required in your project plans —
such as roofs over and berms around trash and recycling areas — and Operational BMPs, such as regular
sweeping and “housekeeping”, that must be implemented by the site’s occupant or user. The MEP
standard typically requires both types of BMPs. In general, Operational BMPs cannot be substituted for a
feasible and effective permanent BMP. Using the Pollutant Sources/Source Control Checklist in Appendix
8, review the following procedure to specify Source Control BMPs for your site:
1. Identify Pollutant Sources: Review Column 1 in the Pollutant Sources/Source Control Checklist. Check
off the potential sources of Pollutants that apply to your site.
2. Note Locations on Project-Specific WQMP Exhibit: Note the corresponding requirements listed in
Column 2 of the Pollutant Sources/Source Control Checklist. Show the location of each Pollutant
source and each permanent Source Control BMP in your Project-Specific WQMP Exhibit located in
Appendix 1.
3. Prepare a Table and Narrative: Check off the corresponding requirements listed in Column 3 in the
Pollutant Sources/Source Control Checklist. In the left column of Table G.1 below, list each potential
source of runoff Pollutants on your site (from those that you checked in the Pollutant Sources/Source
Control Checklist). In the middle column, list the corresponding permanent, Structural Source Control
BMPs (from Columns 2 and 3 of the Pollutant Sources/Source Control Checklist) used to prevent
Pollutants from entering runoff. Add additional narrative in this column that explains any special
features, materials or methods of construction that will be used to implement these permanent,
Structural Source Control BMPs.
4. Identify Operational Source Control BMPs: To complete your table, refer once again to the Pollutant
Sources/Source Control Checklist. List in the right column of your table the Operational BMPs that
should be implemented as long as the anticipated activities continue at the site. Copermittee
stormwater ordinances require that applicable Source Control BMPs be implemented; the same BMPs
may also be required as a condition of a use permit or other revocable Discretionary Approval for use
of the site.
Table G.1 Permanent and Operational Source Control Measures
Potential Sources of Runoff
pollutants
Permanent Structural Source
Control BMPs
Operational Source Control BMPs
On-site storm drain inlets*
Mark all inlets with the
words “Only Rain Down the
Storm Drain” or similar.
Catch Basin Markers may
be available from the
Riverside County Flood
Control and Water
Conservation District, call
951.955.1200 to verify.
Maintain and periodically repaint or
replace inlet markings.
Provide stormwater pollution prevention
information to new site owners, lessees,
or operators.
See applicable operational BMPs in Fact
Sheet SC-44, “Drainage System
Maintenance,” in the CASQA Stormwater
Quality Handbooks at
www.cabmphandbooks.com
- 23 -
Include the following in lease agreements:
“Tenant shall not allow anyone to
discharge anything to storm drains or to
store or deposit materials so as to create a
potential discharge to storm drains.”
Landscape/Outdoor
Pesticide use*
Final landscape plans will
accomplish all of the
following.
Preserve existing native
trees, shrubs, and ground
cover to the maximum
extent possible.
Design landscaping to
minimize irrigation and
runoff, to promote surface
infiltration where
appropriate, and to
minimize the use of
fertilizers and pesticides
that can contribute to
stormwater pollution.
Where landscaped areas
are used to retain or detain
stormwater, specify plants
that are tolerant of
saturated soil conditions.
Consider using pest-
resistant plants, especially
adjacent to hardscape.
To insure successful
establishment, select plants
appropriate to site soils,
slopes, climate, sun, wind,
rain, land use, air
movement, ecological
consistency, and plant
interactions.
Maintain landscaping using minimum or
no pesticides.
See applicable operational BMPs in “What
you should know for….Landscape and
Gardening” at
https://www.rcwatershed.org/wpcontent/
uploads/2015/12/Landscapingand-
Gardening-Guide.pdf
Provide IPM information to new owners,
lessees, and operators.
Food Service* N/A N/A
Refuse Areas*
Several site refuse trash
enclosures are included in
the proposed plan. Refuse
will be removed from the
site by the City refuse
department/contractors.
Provide adequate number of receptacles.
Inspect receptacles regularly; repair or
replace leaky receptacles. Keep
receptacles covered. Prohibit/prevent
dumping of liquid or hazardous wastes.
Post “no hazardous materials” signs.
Inspect and pick up litter daily and clean
up spills immediately. Keep spill control
- 24 -
Signs will be posted on or
near dumpsters with the
words “Do not dump
hazardous materials here”
or similar.
materials available on-site. See Fact Sheet
SC-34, “Waste Handling and Disposal” in
the CASQA Stormwater Quality
Handbooks at
www.cabmphandbooks.com
Loading docks*
N/A
Move loaded and unloaded items indoors
as soon as possible.
See Fact Sheet SC-30, “Outdoor Loading
and Unloading,” in the CASQA Stormwater
Quality Handbooks at
www.cabmphandbooks.com
Fire Sprinkler Test Water*
Provide a means to drain
fire sprinkler test water to
the sanitary sewer.
See the note in Fact Sheet SC-41, “Building
and Grounds Maintenance,” in the CASQA
Stormwater Quality Handbooks at
www.cabmphandbooks.com
Miscellaneous Drain or
Wash Water or Other
Sources:
Condensate drain lines
Rooftop equipment
Roofing, gutters, and trim.
Condensate drain lines may
discharge to landscaped
areas if the flow is small
enough that runoff will not
occur. Condensate drain
lines may not discharge to
the storm drain system.
Rooftop equipment with
potential to produce
pollutants shall be roofed
and/or have secondary
containment.
Avoid roofing, gutters, and
trim made of copper or
other
unprotected metals that
may leach into runoff.
N/A
Plazas, sidewalks, and
parking *lots* N/A
Sweep plazas, sidewalks, and parking lots
regularly to prevent accumulation of litter
and debris. Collect debris from pressure
washing to prevent entry into the storm
drain system. Collect washwater
containing any cleaning agent or
degreaser and discharge to the sanitary
sewer not to a storm drain.
*See Appendix 8
- 25 -
Section H: Construction Plan Checklist (To be Filled out in Final WQMP)
Populate Table H.1 below to assist the plan checker in an expeditious review of your project. The first two
columns will contain information that was prepared in previous steps, while the last column will be
populated with the corresponding plan sheets. This table is to be completed with the submittal of your
final Project-Specific WQMP.
Table H.1 Construction Plan Cross-reference
BMP No. or ID BMP Identifier and Description Corresponding Plan Sheet(s)
Units A-K Filterra Bioretention/BioFiltration Systems TBD Storm Drain Plans
Note that the updated table — or Construction Plan WQMP Checklist — is only a reference tool to facilitate
an easy comparison of the construction plans to your Project-Specific WQMP. Co-Permittee staff can
advise you regarding the process required to propose changes to the approved Project-Specific WQMP.
- 26 -
Section I: Operation, Maintenance and Funding
The Copermittee will periodically verify that Stormwater BMPs on your site are maintained and continue
to operate as designed. To make this possible, your Copermittee will require that you include in Appendix
9 of this Project-Specific WQMP:
1. A means to finance and implement facility maintenance in perpetuity, including replacement
cost.
2. Acceptance of responsibility for maintenance from the time the BMPs are constructed until
responsibility for operation and maintenance is legally transferred. A warranty covering a period
following construction may also be required.
3. An outline of general maintenance requirements for the Stormwater BMPs you have selected.
4. Figures delineating and designating pervious and impervious areas, location, and type of
Stormwater BMP, and tables of pervious and impervious areas served by each facility. Geo-
locating the BMPs using a coordinate system of latitude and longitude is recommended to help
facilitate a future statewide database system.
5. A separate list and location of self-retaining areas or areas addressed by LID Principles that do
not require specialized O&M or inspections but will require typical landscape maintenance as
noted in Chapter 5, pages 85-86, in the WQMP Guidance. Include a brief description of typical
landscape maintenance for these areas.
Your local Co-Permittee will also require that you prepare and submit a detailed Stormwater BMP
Operation and Maintenance Plan that sets forth a maintenance schedule for each of the Stormwater BMPs
built on your site. An agreement assigning responsibility for maintenance and providing for inspections
and certification may also be required.
Details of these requirements and instructions for preparing a Stormwater BMP Operation and
Maintenance Plan are in Chapter 5 of the WQMP Guidance Document.
Maintenance Mechanism: Home Owner’s Association (HOA)
Will the proposed BMPs be maintained by a Home Owners’ Association (HOA) or Property Owners
Association (POA)?
Y N
Include your Operation and Maintenance Plan and Maintenance Mechanism in Appendix 9. Additionally,
include all pertinent forms of educational materials for those personnel that will be maintaining the
proposed BMPs within this Project-Specific WQMP in Appendix 10.
- 27 -
Appendix 1: Maps and Site Plans
Location Map, WQMP Site Plan and Receiving Waters Map
CORPORATIONWILSON MIKAMI····
- 28 -
Appendix 2: Construction Plans
Grading and Drainage Plans
Site Plan
LOT 1BBCCDDDDEEEEDDDDEEEEEEEEEEEEEEFFFFHHGGAAGGEEWILSON MIKAMICORPORATIONPREPARED BY:OWNER:SHEETOF1DESCRIPTIONDATEREVISIONAPPROVEDTENTATIVE TRACT NO. 3837818 ACRE PROPERTY - LAKESHORE DRIVESUBDIVIDER:CIVILExp.FOR CONDOMINIUM PURPOSESPROJECT LOCATIONVICINITY MAPSECTION "D-D"(TYPICAL STREET)SECTION "C-C"(ENTRY STREET)SECTION "B-B"(ENTRY STREET)SECTION "E-E"(TYP. MOTOR COURT)WATER & SEWERELSINORE VALLEY MUNICIPALWATER DISTRICT (EVMWD)31315 CHANEY STREETLAKE ELSINORE, CA 92530ELECTRICSOUTHERN CALIFORNIA EDISON32815 FREESIA WAYTEMECULA, CA 92592GASSOUTHERN CALIFORNIA GASCOMPANY25620 JEFFERSON AVE.MURRIETA, CA 92562TELEPHONE / CABLE TELEVISIONVERIZON / GTE - (800) 483-1000AT&T - (800) 310-2355TIME WARNER - (888) 354-9622STORMWATERCITY OF LAKE ELSINORE130 SOUTH MAIN ST.LAKE ELSINORE, CA 92530WASTE MANAGEMENTCR&R1706 GOETZ RD.PERRIS, CA 92570ASSESSOR PARCEL NUMBERS370-050-019370-050-020370-050-032PROPOSED PHASINGSINGLE PHASE CONSTRUCTIONA. OFFSITE IMPROVMENTSWITHIN LAKESHORE DRIVEB. ROUGH GRADINGC. ONSITE & OFFSITE UTILITIESD. PRECISE GRADINGF. BUILDING CONSTRUCTIONF. SITEWORK & LANDSCAPING’ ” ’ ” C.1ENGINEER'S NOTESPUBLIC PARK DEDICATIONDATE OF FILING: 10/18/22THE DEVELOPMENT AT MISSION TRAILS -LAKE ELSINORE, LLCLAKE ELSINORE MISSION TRAIL. LLCVICTORIAN LANE(TYPICAL STREET)FUTURE IMPROVEMENTSASUBDIVISION LOT SUMMARYLOT 1: CONDOMINIUM DEVELOPMENT LOT EXISTING RIGHT OF WAY RIGHT OF WAY DEDICATION NET SITE AREA****NET SITE AREA INCLUDES COMMON OPENSPACE, PRIVATE STREETS, AND EASEMENTSPER BELOW:COMMON OPEN SPACEPRIVATE STREETSEASEMENTSAREA (SF)749,850-12,140737,61053,924228,647228,647AREA (AC)17.21-0.2816.931.245.255.25
WILSON MIKAMICORPORATIONPREPARED BY:OWNER:SHEETOF1DESCRIPTIONDATEREVISIONAPPROVEDTENTATIVE TRACT NO. 3837818 ACRE PROPERTY - LAKESHORE DRIVESUBDIVIDER:CIVILExp.FOR CONDOMINIUM PURPOSESC.1 (2)LAKE ELSINORE MISSION TRAIL. LLCLAKE ELSINORE MISSION TRAIL. LLC
COMMON OPEN SPACELOT A LOT ALOT D
LOT 1STREET "A"STREET "A"STREET "A"STREET "A"STREET "A"CORPORATIONWILSON MIKAMI03/04/2022 1st SUBMITTALJurisdiction #LAKE ELSINORE, CAWMC PROJECT NO. 10397.00LAKE ELSINORE MISSION TRAIL, LLC1020 Second St., Suite CEncinitas, CA 92024949.632.312218 ACRE PROPERTY - MISSION TRAILGRADING & DRAINAGEC.2EARTHWORK SUMMARYRAW CUT:24,000 CYRAW FILL: 21,690 CYSHRINKAGE (10%):(2,410) CYNET: 0 CYNOTE:EARTHWORK QUANTITIES DO NOT INCLUDEDREMEDIAL GRADING QUANTITIES ANDADJUSTMENTS FOR SUBSIDENCE.
F.E.LOT 1
CORPORATION
WILSON MIKAMI
03/04/2022 1st SUBMITTALJurisdiction #
LAKE ELSINORE, CA
WMC PROJECT NO. 10397.00
LAKE ELSINORE MISSION TRAIL, LLC
1020 Second St., Suite C
Encinitas, CA 92024
949.632.3122
18 ACRE PROPERTY - MISSION TRAIL SITE PLAN C.3CIVIL
Exp.
680'
SITE SUMMARYRESIDENTIAL PARKING SUMMARYGENERAL PLAN DESIGNATION:EXISTING ZONING DESIGNATION:
EXISTING LAND USE:
FOR CONDOMINIUM PURPOSES
EAST LAKE SPECIFIC PLAN MIXED USE OVERLAY
CORPORATIONWILSON MIKAMILAKE ELSINORE, CAWMC PROJECT NO. 10397.00LAKE ELSINORE MISSION TRAIL, LLC1020 Second St., Suite CEncinitas, CA 92024949.632.312218 ACRE PROPERTY - MISSION TRAILCONCEPT UTILITY PLANC.476
F.E.CORPORATIONWILSON MIKAMILAKE ELSINORE, CAWMC PROJECT NO. 10408.00LAKE ELSINORE MISSION TRAIL, LLC1020 Second St., Suite CEncinitas, CA 92024949.632.312218 ACRE PROPERTY - MISSION TRAILMAINTENANCE PLANC.5LEGENDMAINTENANCERESPONSIBILITY76
- 29 -
Appendix 3: Soils Information
Geotechnical Study and Other Infiltration Testing Data
- 30 -
Appendix 4: Historical Site Conditions (N/A)
Phase I Environmental Site Assessment or Other Information on Past Site Use
Not Applicable
- 31 -
Appendix 5: LID Infeasibility
LID Technical Infeasibility Analysis
- 32 -
LID Infeasibility Analysis:
The Project (18-acre Site on Mission Trail - Tentative Tract 38378) is proposing an Alternative
Compliance Treatment Control BMP for the project due to the infeasibility of Bioretention at the site
based on the following information/constraints.
• A Bioretention basin at the site will require an underdrain due to infiltration being not applicable
per Section D.1 of the WQMP. In addition, Silty/Clayey soil found on-site provides low
infiltration rates that makes infiltration on-site infeasible.
• A Bioretention basin underdrain must discharge to a downstream storm drain. The depth of
the underdrain is approximately 4-4.5 ft deep below the finish surface of the Bioretention basin.
The existing downstream storm drain for the site is located approximately 1,525 ft from the
Bioretention basin underdrain location. The depth of the storm drain at that location is 3.2 ft
which is 1.3 ft higher than the underdrain. The Site grading would need to be raised 1.3 ft in
order to connect the underdrain to the storm drain. The site grading is balance (24,000 cut and
fill). Raising the site 1.3 feet would result in excess of 30,000 cy of imported soil which is not
feasible.
• Proposed retaining walls on the northwest side of the site would need to be increased to 8 ft
high with an additional 8 ft high sound wall on top. This configuration is not considered feasible.
A Bioretention basin will require an area of approximately 19,000 square feet within the private
park area within the site. The basin would use approximately 50% of the park area which will
eliminate amenities and make that area unusable for residents. The use of a alternative
compliance BMP results in a much more livable community.
- 33 -
Appendix 6: BMP Design Details
BMP Sizing, Design Details and other Supporting Documentation
- 34 -
Filterra Bioretention/Biofiltration System Units BMP Sizing Calculations
Table of Contents
1. Alternative Compliance Documents for Filterra Bioretention/Biofiltration System:
a. Los Angeles Los Angeles Regional Water Quality Control Board Approval of
Alternative Biofiltration Specification (4 Pages)
b. Filterra Equivalency Analysis and Design Criteria pursuit to Los Angeles County
MS4 Permit, Geosyntec Consultants (50 Pages)
i. Documents the Treatment Equivalency Analysis between the Filterra
Bioretention/Biofiltration and Conventional Bioretention/Biofiltration (LID
BMP)
ii. Efficiency Pollutant Removal Rates for Pesticides, Sediment, Trash and
Debris and Oil and Grease as Pollutants of Concern: See Section 3.3
Pages 5 through 11
iii. BMP Design Methodology: See Section 4, Pages 12-15
2. Filterra Bioretention Systems: Technical Basis for High Flow Rate Treatment and
Evaluation of Stormwater Quality Performance, Herrera Environmental Consultants (39
Pages): Additional Reference Study for Filterra Stormwater Quality Performance
3. BMP Design Calculations (12 Pages)
4. BMP Sizing Specification and Typical Plans/Details (12 Pages)
Los Angeles Regional Water Quality Control Board
December 30, 2019
Paul Alva
Assistant Deputy Director
County of Los Angeles
900 South Fremont Avenue
Alhambra, CA 91803
VIA EMAIL
APPROVAL OF ALTERNATIVE BIOFILTRATION SPECIFICATION PURSUANT TO
PART VI.D.7.c.iii.(1)(b)(i) OF THE LOS ANGELES COUNTY MUNICIPAL SEPARATE
STORM SEWER SYSTEM (MS4) PERMIT (NPDES PERMIT NO. CAS004001;
ORDER NO. R4-2012-0175 AS AMENDED BY STATE WATER BOARD ORDER WQ
2015-0075 AND LOS ANGELES WATER BOARD ORDER R4-2012-0175-A01)
Dear Mr. Alva:
On June 20, 2019, and August 8, 2019 for the City of Lomita, the Los Angeles Regional
Water Quality Control Board (Los Angeles Water Board) received a letter from the
County of Los Angeles (County), on behalf of the Contract Cities,1 requesting approval
for the use of Filterra Bioretention Systems (Filterra) manufactured by Contech
Engineered Solutions LLC as an alternative biofiltration design specification.
The County’s request includes an excerpt from a document entitled “Filterra
Equivalency Analysis and Design Criteria” (Equivalency Analysis) as an attachment,
that details a proposed design approach and equivalency criteria for Filterra to achieve
equivalent performance to the biofiltration design specifications defined in the Los
Angeles County MS4 Permit.
Pursuant to Part VI.D.7.c.iii.(1)(b)(i) of the Los Angeles County MS4 Permit, projects
using biofiltration as an alternative compliance measure may use alternative design
1 The County of Los Angeles provides land development review services for the cities of
Carson, Irwindale, La Cañada Flintridge, Lomita, Rolling Hills Estates and Westlake
Village (Contract Cities).
Mr. Paul Alva - 2 - December 30, 2019
County of Los Angeles
specifications for on-site biofiltration systems if approved by the Los Angeles Water
Board Executive Officer.
Background
Part VI.D.7 of the Los Angeles County MS4 Permit requires Permittees to implement a
Planning and Land Development Program. As part of this program, Permittees shall
require all New Development and Redevelopment projects identified in Part VI.D.7.b
(hereinafter “new projects”) to control pollutants, pollutant loads, and runoff volume
emanating from the project site. Except as provided in Part VI.D.7.c.ii (Technical
Infeasibility or Opportunity for Regional Ground Water Replenishment), Part VI.D.7.d.i
(Local Ordinance Equivalence), or Part VI.D.7.c.v (Hydromodification), each Permittee
shall require new projects to retain on-site the Stormwater Quality Design Volume
(SWQDv).
Pursuant to Part VI.D.7.c.iii.(1) of the Los Angeles County MS4 Permit, Permittees may
allow new projects to use on-site biofiltration when the project applicant has
demonstrated that it is technically infeasible to retain 100 percent of the Stormwater
Quality Design Volume (SWQDv) on-site. If a Permittee conditions a project using
biofiltration due to demonstrated technical infeasibility, then the new project must
biofiltrate 1.5 times the portion of the SWQDv that is not reliably retained on-site, as
calculated by the following equation:
Where: Bv = biofiltration volume
SWQDv = the stormwater runoff from a 0.75 inch, 24-hour storm or
the 85th percentile storm, whichever is greater
Rv = volume reliably retained on-site
As a condition for on-site biofiltration, bioretention/biofiltration systems shall meet the
design specifications provided in Attachment H of the Los Angeles County MS4 Permit
unless otherwise approved by the Los Angeles Board Executive Officer.
Public Review
On September 30, 2019, the Los Angeles Water Board provided public notice and a 30-
day period to allow for public review and written comment on the proposed use of
Filterra alternative biofiltration design specification. No comments were received.
Alternative Biofiltration Specification Approval
I hereby approve the County’s proposal for the use of Filterra as an alternative on-site
biofiltration design specification pursuant to Part VI.D.7.c.iii(1)(b)(i) of the Los Angeles
County MS4 Permit, provided the following conditions are met:
Mr. Paul Alva - 3 - December 30, 2019
County of Los Angeles
1. Sizing: The County shall verify the appropriateness of the recommended loading
rates used in the “Filterra Equivalency Analysis and Design Criteria”.
If the County finds no issues with the loading rate, Filterra systems must be
designed and sized following the methodology in Section 4 of the August 2015
report entitled “Filterra Equivalency Analysis and Design Criteria”.
If the County finds that the recommended loading rate is too high, Filterra
systems must be designed and sized to account for an appropriate lower loading
rate.
2. O&M: Operation and maintenance of Filterra systems must be conducted
consistent with the recommendations in the Filterra maintenance manual
provided by the manufacturer and any revisions thereto.
3. Media: Filterra systems use an engineered biofiltration media. Filterra systems,
including the engineered biofiltration media, must be provided by the
manufacturer. No substitution of materials/media is allowed.
4. Hydromodification: There is no presumption by this approval that a Permittee’s
implementation of the abovementioned design parameters and use specifications
of the Filterra system meet the separate hydromodification requirements of
Section VI.D.7.c.iv of the Los Angeles County MS4 Permit. Hydromodification
requirements apply regardless of the type of biofiltration system used.
This approval only applies to the use of Filterra as an alternative on-site biofiltration
design in situations where a project applicant has demonstrated that it is technically
infeasible to retain 100 percent of the SWQDv on-site. Furthermore, this approval does
not constitute certification or verification of the performance of the Filterra since the Los
Angeles Water Board does not have a testing and certification program for treatment
control BMPs. This approval is given based on the supporting documentation provided
in the request and relies on the County’s review of the system.
The County shall comply with Maintenance Agreement and Transfer requirements
outlined in Part VI.D.7.d.iii of the Los Angeles County MS4 Permit. These requirements
include:
1. Part VI.D.7.d.iii – prior to issuing approval for final occupancy, the County shall
require new development and redevelopment projects subject to post-
construction BMP requirements to provide an operation and maintenance plan;
monitoring plan, where required; and verification of ongoing maintenance
provisions for LID practices, treatment control BMPs, and hydromodification
control BMPs.
2. Part VI.D.7.d.iii.(1)(a) – verification of post-construction BMP maintenance
agreement shall include all the documents included in this provision.
Mr. Paul Alva - 4 - December 30, 2019
County of Los Angeles
3. Part VI.D.7.d.iii.(1)(b) – the County shall ensure a plan is developed for the
operation and maintenance of all structural and treatment controls. The County
shall examine the plan for relevance to keeping the BMPs in proper working
order. Furthermore, operation and maintenance plans for private BMPs shall be
kept on-site for periodic review by County inspectors.
4. Part VI.D.7.d.iv.(c) – the County shall verify proper maintenance and operation of
post-construction BMPs operated by the County.
5. Part VI.D.7.d.iv.(d) – for post-construction BMPs operated and maintained by
parties other than the County, the County shall require the other parties to
document proper maintenance and operations.
6. Part VI.D.7.d.iv.(e) – the County shall undertake any enforcement as appropriate
per the established progressive enforcement policy.
If you have any questions, please contact Ms. Susana Vargas of the Storm Water
Permitting Unit at Susana.Vargas@waterboards.ca.gov or by phone at (213) 576-6688.
Alternatively, you may also contact Ivar Ridgeway, Chief of the Storm Water Permitting
Unit, at Ivar.Ridgeway@waterboards.ca.gov or by phone at (213) 620-2150.
Sincerely,
Renee Purdy
Executive Officer
FILTERRA EQUIVALENCY ANALYSIS
AND DESIGN CRITERIA
Pursuant to:
Los Angeles County MS4 Permit
(Order R4-2012-0175)
Prepared for
CONTECH Engineered Solutions
Prepared by
621 SW Morrison Street, Suite 600
Portland, Oregon 97205
August 2015
Filterra Equivalency Analysis
August 2015
i
TABLE OF CONTENTS
Table of Contents ............................................................................................................... i
1 Introduction ........................................................................................................... 1
2 BMP descriptions .................................................................................................. 2
2.1 Conventional Biofiltration ........................................................................... 2
2.2 Filterra Systems ........................................................................................... 2
3 Basis and Methdology for Evaluating Equivalency .............................................. 4
3.1 Basis for Equivalency .................................................................................. 4
3.2 Methods and Assumptions for Establishing Baseline Biofiltration
Performance ................................................................................................. 4
3.2.1 Hydrologic Performance (Capture Efficiency and Volume Reduction)
........................................................................................................ 4
3.2.2 Pollutant Treatment ........................................................................ 5
3.3 Filterra Analysis to Determine Equivalent Design Criteria ......................... 6
3.3.1 Capture Efficiency .......................................................................... 6
3.3.2 Volume Reduction (Filterra and Supplemental Infiltration Storage)7
3.3.3 Pollutant Treatment ........................................................................ 8
3.3.4 Additional Capture In Lieu of Volume Reduction ......................... 9
4 Design Methodology and Equivalency Criteria .................................................. 12
5 Discussion and Conclusions ............................................................................... 16
5.1 Key Observations and Findings ................................................................. 16
5.2 Reliability and Limitations ........................................................................ 17
6 References ........................................................................................................... 19
Appendix A – Conventional Biofiltration Design Assumptions for Performance Modeling
21
Appendix B – SWMM Modeling Methodology and Assumptions ................................ 23
Equivalency Scenarios ........................................................................................ 23
Overview of SWMM Analysis Framework ........................................................ 23
Meteorological Inputs ......................................................................................... 25
Precipitation ............................................................................................... 25
ET Parameters ............................................................................................ 26
Runoff Parameters .............................................................................................. 27
BMP Representation ........................................................................................... 28
Conventional Biofiltration ......................................................................... 29
Filterra 30
Appendix C – Datasets and Analysis Methods for Pollutant Treatment Evaluation ...... 32
Data Development and Analysis Framework ..................................................... 32
Filterra Equivalency Analysis
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ii
Compilation and Screening of Conventional Biofiltration Studies .................... 32
Screening Process for Developing Conventional Biofiltration Sample Pool32
Screening Results ....................................................................................... 35
Inventory of Bioretention Studies and Screening Results/Rationales ....... 35
Compilation of Filterra Studies ........................................................................... 36
Data Analysis Method......................................................................................... 37
Land Use Stormwater Quality Inputs and Assumptions ..................................... 38
Appendix D – Results of Pollutant Treatment Data Analysis ........................................ 42
Filterra Equivalency Analysis
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1 INTRODUCTION
The Los Angeles County MS4 Permit (Order No. R4-2012-0175) (MS4 Permit) defines
“biofiltration” based on specific design and sizing criteria1. In addition, the MS4 Permit allows
the Los Angeles County Regional Water Quality Control Board (Regional Board) Executive
Officer to approve alternate biofiltration design criteria. The purpose of this analysis was to
develop a design basis for Filterra systems such that these systems will provide reasonably
equivalent performance to biofiltration BMPs as defined in the MS4 Permit. This report is
provided to the Executive Officer of the Regional Board to support approval of alternative design
criteria for Filterra systems. This report describes the basis for evaluating equivalency, details the
design approach and equivalency criteria for Filterra systems to achieve equivalent performance
to conventional biofiltration, and provides the supporting rationales for these equivalency
criteria.
The remainder of this report is organized as follows:
Section 2 – BMP Descriptions
Section 3 – Basis and Methodology for Evaluating Equivalency
Section 4 – Filterra Design Approach and Equivalency Criteria
Section 5 – Discussion and Conclusions
Section 6 – References
Appendix A – Design Assumptions for Conventional Biofiltration
Appendix B – SWMM Modeling Methodology and Assumptions
Appendix C – Datasets and Analysis Methods for Pollutant Treatment Evaluation
Appendix D – Results of BMP Treatment Performance Evaluation
1 BMPs sized and designed per these criteria are referred to in this memorandum as “traditional biofiltration.”
Filterra Equivalency Analysis
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2 BMP DESCRIPTIONS
2.1 Conventional Biofiltration
Biofiltration (also known as bioretention with underdrain) consists of shallow landscaped
depressions that capture and filter stormwater runoff through a planted engineered media. These
facilities function as soil and plant-based filtration systems that remove pollutants through a
variety of physical, biological, and chemical treatment processes. Biofiltration facilities normally
consist of a ponding area, mulch layer, planting soils, and plantings (see typical schematic in
Figure 1). An optional gravel layer added below the planting soil coupled with an upturned
elbow (or similar hydraulic control approach) can provide additional storage volume for
infiltration. As stormwater passes down through the planting soil, pollutants are filtered,
adsorbed, and biodegraded by the soil and plants. As defined in Attachment H of the 2012 Los
Angeles County MS4 Permit, biofiltration designs must meet a number of specific criteria to be
considered “biofiltration” as part of compliance with the MS4 Permit. Conventional biofiltration
is typically designed as a “volume-based” BMP, meaning that is it sized based on capture of the
runoff from a specific size of storm event.
Figure 1. Cross sections of typical biofiltration system
2.2 Filterra Systems
Filterra systems include engineered filter media topped with mulch housed in a precast concrete
curb inlet structure with a tree frame and grate cast in the top slab. In addition to the water
quality filtering/sorption of stormwater, the engineered media and mulch supports the growth of
a tree or other type of plant (see typical configuration in Figure 2). There are three key
components of the Filterra system that contribute to pollutant removal: mulch, engineered filter
media, and vegetation and other system biota. Filterra systems can be configured so that
underdrains discharge into downstream retention storage systems. In contrast to conventional
Filterra Equivalency Analysis
August 2015
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biofiltration, the media filtration rates of Filterra systems are substantially higher, and therefore
the footprint of these systems tends to be substantially smaller than conventional biofiltration
systems. As a result of smaller footprints, the amount of volume reduction (via infiltration and
evapotranspiration) that is typically observed in these systems when not coupled with infiltration
systems tends to be relatively low. Because these systems provide relatively limited ponded
water volume above the surface of the media, they are typically sized as “flow-based” BMPs
based on a design intensity of rainfall rather than “volume-based” BMP based on a design storm
depth.
Figure 2. Diagram of the Filterra system (Contech, 2015 via web).
Filterra Equivalency Analysis
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3 BASIS AND METHDOLOGY FOR EVALUATING EQUIVALENCY
3.1 Basis for Equivalency
Equivalency was evaluated between conventional biofiltration BMPs meeting the criteria of the
MS4 Permit (specifically Attachment H) and Filterra systems as an alternate biofiltration BMP.
Equivalency was determined based on the factors that influence the pollutant load reduction
performance of stormwater BMPs:
Capture efficiency: The percent of long term stormwater runoff volume that is
“captured” and managed by the BMP (i.e., treated or reduced; not overflowed or
bypassed).
Volume reduction: The percent of long term stormwater runoff volume that is “lost” or
“reduced” in the BMP to infiltration and evapotranspiration.
Concentration reduction: For the volume that is treated and not reduced, the average
difference in concentration between the influent volume and the treated effluent volume.
The equivalency analysis consisted of three parts:
1) The baseline performance of conventional biofiltration (capture efficiency, volume
reduction, and concentration reduction) was estimated.
2) Applying the same methods as used to evaluate the performance of conventional
biofiltration, sizing criteria were developed for Filterra (accompanied by supplemental
infiltration systems, where needed) such that Filterra systems will provide equivalent
performance to conventional biofiltration.
3) A design methodology for Filterra systems was developed to ensure consistent
application of the equivalent sizing criteria in the design of Filterra systems.
The following subsections provide information about this analysis.
3.2 Methods and Assumptions for Establishing Baseline Biofiltration Performance
The following subsections summarize the methods and assumptions that were used to evaluate
the baseline performance of conventional biofiltration BMPs consistent with Attachment H of
the MS4 Permit.
3.2.1 Hydrologic Performance (Capture Efficiency and Volume Reduction)
Attachment H of the MS4 Permit specifies a number of criteria that influence the hydrologic
performance of the conventional biofiltration BMPs:
6 to 18-inch ponding area above media
Optional layer of mulch
2 to 3 feet of engineered filter media (2 feet typical) with a design infiltration rate of 5 to
12 inches/hour; the Attachment H specification calls for a mix of 60 to 80% fine sand and
20 to 40% compost
Filterra Equivalency Analysis
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Gravel storage layer below the bioretention media to promote infiltration
Underdrain placed near the top of the gravel layer (or an infiltration sump otherwise
provided via an equivalent hydraulic control approach) in cases where underlying soil
allows incidental infiltration
Underdrain discharge to the storm drain
Capacity (including stored and filtered water) adequate to biofilter 150 percent of the
portion of the SWQDv not reliably retained.
Within the bounds established by these criteria, a relatively wide range of actual biofiltration
designs could result as a function of site infiltration conditions as well as designer and local
jurisdiction preferences. An example of potential design variability is illustrated in Appendix A.
For the purpose of this analysis, representative design assumptions were developed within the
range of potential design assumptions. These assumptions are also presented in Appendix A with
supporting rationales. Long term continuous simulation SWMM modeling was conducted using
15 years of 5-minute resolution precipitation data, as described in Appendix B, to estimate the
long term capture efficiency and volume reduction of the baseline biofiltration design scenario
for a range of site infiltration rates. Biofiltration BMPs will tend to provide more volume
reduction when installed in sites with higher incidental infiltration rates. Table 1 describes the
baseline hydrologic performance of biofiltration BMPs.
Table 1. Baseline Biofiltration Hydrologic Performance
Site Soil Infiltration Rate,
in/hr
Long Term Capture Efficiency
(percent of total runoff
volume)
Long Term Volume Reduction
(percent of total runoff
volume) (ET + Infiltration)
0
92 to 94%1
(93% capture is
representative)
4%
0.01 6%
0.05 11%
0.15 22%
0.302 35%
1 - Capture efficiency varies slightly as a function of soil infiltration rate (and associated differences in design
profile) and land use imperviousness. These differences are relatively minor and are considered to be less important
than the variability in performance that may result from different design approaches and maintenance conditions that
may be encountered. Therefore a single baseline value of 93 percent long term capture was used in this analysis.
2 - A maximum soil infiltration rate of 0.3 inches per hour was evaluated because for soil infiltration rates greater
than 0.3 inches per hour the MS4 Permit requires that infiltration be evaluated.
3.2.2 Pollutant Treatment
Pollutant treatment performance was evaluated based on analysis of bioretention with underdrain
studies in the International Stormwater BMP Databases. Analyses were conducted based on all
studies (28 studies) and a screened subset of studies that were considered to be most
representative of Attachment H design criteria (16 studies). Additionally, two recent studies from
the University of Maryland were added which followed rigorous protocols and evaluated systems
sharing many similarities to Attachment H design criteria. Biofiltration research in California is
very limited. Two recent monitoring studies were conducted in the San Francisco Bay area (led
Filterra Equivalency Analysis
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6
by the San Francisco Estuary Institute) on systems with media composition, sizing and design
that would conform to Attachment H of the Los Angeles MS4 Permit. While these studies did
not collect flow weighted composite influent and effluent samples, they were included in the data
set.
Treatment performance was characterized using a moving window bootstrapping method that
accounts for the influence of influent concentration on effluent concentration and characterizes
the relative uncertainty in performance estimates within each range of influent quality. Both the
median and mean summary statistics were evaluated using these methods. Additionally,
literature on the influence of biofiltration design variables on performance was summarized to
support the criteria that were used to select the 20 BMP studies that were included in the
screened dataset. The pollutant treatment evaluation was based on total suspended solids, total
phosphorus, total nitrogen, total copper, and total zinc. Influent concentrations characteristic of
single family, multi family, commercial, and light industrial land uses were applied to estimate
effluent concentrations and concentration change.
Generally, biofiltration provided good removal of TSS, moderate removal of copper and zinc,
and generally showed export of nutrients. Export of nutrients tended to be greater when influent
concentrations were low. Also, the dataset that was screened to include studies more similar to
Attachment H design criteria (i.e., 5 to 12 inches per hour, with compost) showed substantially
greater frequency of observed export of nutrients.
Details about pollutant treatment analyses are provided in Appendix C, and results of these
analyses are provided in Appendix D.
3.3 Filterra Analysis to Determine Equivalent Design Criteria
The following paragraphs describe the analyses that were conducted for Filterra systems to
determine the sizing criteria under which Filterra systems provide equivalent performance to
conventional biofiltration.
3.3.1 Capture Efficiency
Filterra capture efficiency is a function of the design precipitation intensity used in sizing the
Filterra system and the time of concentration (Tc) of the tributary area. Continuous simulation
modeling using the SWMM model, with 15 years of 5-minute resolution precipitation, as
described in Appendix B, was used to determine the relationship between design precipitation
intensity, Tc, and long term capture efficiency (Figure 3). Based on this chart, the design
guidance presented in Section 4 requires that approved methods, appropriate for the site, are used
for calculating Tc and selecting a runoff coefficient equation to convert the design intensity to a
design flowrate.
Filterra Equivalency Analysis
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Figure 3. Chart of Filterra Capture Efficiency
3.3.2 Volume Reduction (Filterra and Supplemental Infiltration Storage)
Filterra systems, sized within the range needed to match conventional biofiltration capture
efficiency, were estimated to provide approximately 1 percent long term volume reduction via
evapotranspiration from soil pores (determined from SWMM modeling described above). This
relatively small value is a function of the relatively small surface area of typical Filterra systems.
For site conditions in which conventional biofiltration BMPs would achieve appreciable volume
reduction, supplemental infiltration systems (located either upstream or downstream of Filterra
systems) may be needed to result in volume reduction equal to what would be achieved by
conventional biofiltration BMPs under the same site conditions. Volume reduction is a function
of the storage volume provided, the surface area of the storage/soil interface, and the infiltration
rate of the soil (and associated drawdown time of the stored water). As described in Appendix B,
SWMM modeling was conducted to determine the long term volume reduction of supplemental
infiltration storage as a function of storage volume (with a reasonable surface area) and soil
infiltration rate (Figure 4). The supplemental retention volume is specified as a fraction of the
site-specific SWQDv, which is a standardized calculation in each jurisdiction and accounts for
different precipitation depths around Los Angeles County as well as infiltration rates. The design
methodology (Section 4) also provides guidance about the allowable depth of the supplemental
retention storage systems so that stored water will infiltrate in a reasonable amount of time.
80%
82%
84%
86%
88%
90%
92%
94%
96%
98%
100%
0.2 0.3 0.4 0.5 0.6 0.7 0.8Long Term Capture Efficiency (% of Total Runoff Volume) Filterra Design Precipitation Intensity, in/hr
Tc = 5 min Tc = 10 min Tc = 15 min Tc = 20 min Tc = 30 min
Baseline Capture Efficiency Target = 93%
Filterra Equivalency Analysis
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Figure 4. Chart of Volume Reduction in Supplemental Infiltration Storage
3.3.3 Pollutant Treatment
Filterra performance data were analyzed using the same moving window bootstrapping methods
used for conventional biofiltration. Data from 6 third party studies conducted over the last 11
years (including some studies monitored periodically since 2007) were utilized in this analysis.
This analysis sought to determine whether Filterra performance is reasonably similar to the
treatment performance of conventional biofiltration BMPs under representative ranges of
influent quality. This analysis was based on the same pollutant and land uses described above for
conventional biofiltration.
The following bullets summarize the comparison of pollutant concentration reduction for
conventional biofiltration and Filterra systems. Detailed comparison tables and plots are
provided in Appendix D.
TSS: Filterra performed somewhat better than conventional biofiltration systems for TSS
across all representative land use concentrations considered. Both systems showed
relatively strong performance for TSS.
Copper and Zinc: Performance was generally similar between Filterra and conventional
biofiltration for copper and zinc. Filterra showed better performance for some
representative influent concentrations and conventional biofiltration showed better
concentration reductions for others. In general, both provided moderate concentration
0%
10%
20%
30%
40%
50%
60%
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5Long Term Volume Reduction ( % of Total Runoff Volume) Supplemental Infiltration Storage Volume (As Fraction of SWQDv)
Underlying Infiltration = 0.01 in/hr Underlying Infiltration = 0.05 in/hr
Underlying Infiltration = 0.15 in/hr Underlying Infiltration = 0.3 in/hr
Filterra Equivalency Analysis
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reductions of metals. The sample size for Filterra for sites with high metals
concentrations is somewhat small, which results in wider confidence intervals for land
uses with higher concentrations. Specifically, there was only one study (Port of Tacoma
TAPE, station POT2) that had high zinc concentrations; this site was notable/unique in its
high concentrations and the degree of dissolved zinc as a fraction of total zinc. For this
site, average zinc influent concentrations were approximately 1,000 ug/L of which
approximately 85 percent was dissolved zinc, on average. The concentration reductions
for this site were still moderate (approximately 50 percent average removal).
Nitrogen and Phosphorus: Filterra systems appear to provide much better pollutant
concentration reduction than conventional biofiltration for nitrogen and phosphorus.
Filterra does not appear to exhibit the export issues that were noted for conventional
biofiltration within the representative range of land use concentrations considered.
Variability in pollutant reduction performance was also lower for Filterra.
Given these findings, Filterra are expected to provide similar or better pollutant concentration
reduction for all pollutants across the representative site conditions considered.
3.3.4 Additional Capture In Lieu of Volume Reduction
As described in Section 3.3.2 and Section 4, one approach for matching the pollutant load
reduction of conventional biofiltration is to provide supplemental infiltration storage upstream or
downstream of Filterra systems to match the volume reduction that would be achieved by
conventional biofiltration.
For Filterra applications with minor deficiencies in volume reduction compared to conventional
biofiltration, another option is to capture and treat additional long term runoff volume (via
increased sizing) to achieve equivalent load reductions in lieu of providing supplemental
infiltration storage. As a simple approach for minor volume reduction deficiencies, the pollutant
treatment performance of Filterra systems for TSS was used as a simple method. Based o n a
minimum removal efficiency of 80 percent (actual performance is expected to be higher), a BMP
must treat and discharge 5 parts of water for every 4 parts of water that would be lost to
infiltration or ET. This means that for every 1 percent of volume reduction deficit, 1.25 percent
of long term volume must be treated or 0.25 percent additional capture for every 1 percent of
volume reduction deficit. This concept is illustrated in Figure 5. Calculations of required
additional capture efficiency are provided in Table 2.
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Figure 5. Illustration of Additional Capture In Lieu of Volume Reduction (Not to scale)
Table 2. Additional Capture Efficiency in Lieu of Volume Reduction
Site Soil
Infiltration Rate,
in/hr
Attachment H
Biofiltration
Long Term
Volume
Reduction1, 2
Filterra Long
Term Volume
Reduction1
(ET only)
Volume
Reduction
Deficit
Additional
Capture
Efficiency
in Lieu of
Volume
Reduction3
Adjusted
Target
Capture
Efficiency
0 4% 1% 3% 0.8% 93.8%
0.01 6% 1% 5% 1.3% 94.3%
0.05 11% 1% 10% 2.5% 95.5%
0.10 16.5% 1% 15.5% 3.9% 96.9%
0.15 22% 1% 21% 5.3% 98.3%
0.30 35% 1% 34% 8.5% N/A
1 – Based on modeling of ET from soil pores and standing water.
2 – Includes infiltration losses, where feasible
3 – Required additional capture calculated at a rate of 1 part additional for every 4 parts volume reduction deficit.
Attachment H
Biofiltration
Filterra with Increased
Sizing in Lieu of Volume
Reduction
Bypass/Overflow
Treated Discharge In Lieu
of Volume Reduction
Volume Reduction
Treated Discharge
Additional
capture
provided to
offset volume
reduction at
rate of 5 parts
capture to 4
parts volume
reduction
Long Term Average Water Balance
Filterra Equivalency Analysis
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Figure 6. Additional Capture Targets In Lieu of Volume Reduction (same chart as Figure
4, with adjusted axis limits)
90%
91%
92%
93%
94%
95%
96%
97%
98%
99%
100%
0.2 0.3 0.4 0.5 0.6 0.7 0.8Long Term Capture Efficiency (% of Total RUnoff Volume) Filterra Design Precipitation Intensity, in/hr
Tc = 5 min Tc = 10 min Tc = 15 min Tc = 20 min Tc = 30 min
K = 0.01 in/hr (Target = 94.3%)
K = 0.05 in/hr (Target = 95.5%)
K = 0.10 in/hr (Target = 96.9%)
Lines represent
additional capture
efficiency target In lieu
of volume reduction
for each increment of
site infiltration rate
K = 0.15 in/hr (Target = 98.3%)
K = 0 in/hr (Target = 93.8%)
Filterra Equivalency Analysis
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4 DESIGN METHODOLOGY AND EQUIVALENCY CRITERIA
In order to apply the equivalency relationships developed in Section 3, a standardized design
methodology was developed. As a result of applying this design methodology, Filterra systems
are expected to perform equivalently to conventional Attachment H biofiltration. This
methodology consists of three parts, as described below.
Part A - Characterize Site and Determine Key Attributes
1. Delineate the tributary area to each Filterra BMP.
2. Estimate the imperviousness of the tributary area; use this value to estimate a runoff
coefficient for use in stormwater quality design flowrate (SWQDf) and stormwater
quality design volume (SWQDv) calculations. The runoff coefficient shall account for
imperviousness and be based on standard methods acceptable to the reviewing
jurisdiction.
3. Calculate the time of concentration (Tc) for each Filterra tributary area using methods
acceptable to the local jurisdiction.
4. Estimate the long term reliable infiltration rate of the soils underlying each BMP location
using appropriate methods, subject to the approval of the reviewing agency.
5. Determine local 85th percentile, 24-hour precipitation depth for the project. The 85th
percentile, 24-hour rain event shall be determined from the Los Angeles County 85th
percentile precipitation isohyetal map2 or analysis of local long term precipitation data.
6. Calculate the SWQDv for each Filterra tributary area, using locally-approved methods.
7. Calculate the site “Scaling Factor” as the ratio of the project-specific 85th percentile, 24-
hour storm event to the LAX 85th percentile, 24-hour storm event (1.02 inches).
Part B – Design Filterra for Equivalent Long Term Capture Efficiency
8. Consult Design Table 1 to determine the appropriate Filterra Design Precipitation
Intensity associated with the Tc for each tributary area. For Tc less than 5 minutes, round
up to 5 minutes. For Tc greater than 30 minutes, round down to 30 minutes. Interpolation
between values in this table is permissible.
2 http://www.ladpw.org/wrd/publication/engineering/Final_Report-Probability_Analysis_of_85th_Percentile_24-
hr_Rainfall1.pdf
Filterra Equivalency Analysis
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Design Table 1 - Filterra Design Chart for Equivalent Long Term Capture Efficiency
Time of Concentration of Tributary
Area, minutes
Filterra Design Precipitation Intensity,
inches per hour1
5 0.41
10 0.38
15 0.36
20 0.34
30 0.32
1 - Sizing requirements are based on Filterra size required to achieve a target capture efficiency of 93% of
long term runoff volume at the Los Angeles Airport gage. For different locations, the site scaling factor
must be applied.
9. Apply the rational method to determine the design flowrate required for each Filterra.
Qrequired = Runoff Coefficient (unitless) × Filterra Design Precipitation Intensity
(in/hr) × Site Scaling Factor (unitless) × Tributary Area (ac) × (43560
sq-ft/ac/(12 in/ft × 3600 sec/hr))
10. Select a Filterra model with a treatment flow rate that is equal to or greater than the
design flowrate based on a maximum treatment flow rate of 1.45 gallons per minute per
square foot of Filterra surface area. This is equivalent to a treatment rate of 140 inches
per hour.
Part C, Option 1 - Design for Equivalent Long Term Volume Reduction
The design of a Filterra system must mitigate for deficiency in volume reduction compared to
conventional biofiltration. As one option, the designer may include supplemental infiltration,
either upstream or downstream of the Filterra to compensate for the volume reduction deficit
between conventional biofiltration and Filterra systems.
11. Consult Design Table 2 to determine the fraction of the SWQDv that needs to be
provided in supplemental retention. It is appropriate to linearly interpolate within this
table. For long term reliable infiltration rates greater than 0.3 inches per hour, full
infiltration of the SWQDv must be considered.
Filterra Equivalency Analysis
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Design Table 2 - Supplemental Infiltration Volume for Equivalent Long Term Volume Reduction
Estimated Long Term Reliable
Infiltration Rate below Site,
inches per hour
Long Term Volume
Reduction Deficit, % of
Long Term Runoff
Required Supplemental
Infiltration Storage Volume
as Fraction of Local
SWQDv, unitless1
0 3% Not a feasible option; see
Part C, Option 2
0.01 5% 0.15
0.05 10% 0.11
0.15 21% 0.17
0.3 34% 0.26
1 – Values are not expected to follow a continually increasing trend. A 2.1 foot effective depth is assumed
for supplemental storage.
12. Multiply the site-specific SWQDv for each Filterra Tributary area calculated above by
the ratio from Design Table 2 to determine the required supplemental retention volume.
Design Table 2 is based on the assumption that the Contech ChamberMaxx product will
be used, with an equivalent storage depth of 2.1 feet. Shallower or deeper storage would
require different sizing factors. Supplemental calculations can be provided to demonstrate
that an alternative storage configuration would provide equivalent long term volume
reduction.
Part C, Option 2 - Design for Additional Capture In Lieu of Volume Reduction
As an alternative option, the designer may increase the size of the Filterra systems to provide
additional capture in lieu of providing supplemental infiltration volume.
13. Consult Design Table 3 to determine the adjusted design precipitation intensity needed to
compensate for volume reduction deficiency.
Design Table 3 – Upsizing of Filterra to Provide Additional Capture Efficiency in Lieu of Volume Reduction
Time of
Concentration
of Tributary
Area, minutes
Site Infiltration Rate
0 in/hr
Target Capture
Efficiency =
93.8%
0.01 in/hr
Capture
Efficiency
Target =
94.3%
0.05 in/hr
Capture
Efficiency
Target =
95.5%
0.10 in/hr
Capture
Efficiency
Target =
96.9%
0.15 in/hr
Capture
Efficiency
Target = 98.3%
Adjusted Filterra Design Precipitation Intensities, in/hr
5 0.44 0.46 0.52 0.66 NA
10 0.41 0.43 0.48 0.58 NA
15 0.39 0.41 0.45 0.53 0.76
20 0.37 0.38 0.43 0.50 0.68
30 0.34 0.35 0.39 0.46 0.56
NA = additional capture is not a viable option to offset volume reduction in these cases.
Filterra Equivalency Analysis
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14. Apply the rational method to determine the adjusted design flowrate required for each
Filterra.
Qrequired = Runoff Coefficient (unitless) × Adjusted Filterra Design Precipitation
Intensity (in/hr) × Site Scaling Factor (unitless) × Tributary Area (ac) ×
(43560 sq-ft/ac/(12 in/ft × 3600 sec/hr))
15. Select a Filterra model with a treatment flow rate that is equal or greater than Qrequired
based on a maximum treatment flow rate of 1.45 gallons per minute per square foot of
Filterra surface area (140 inches per hour).
Filterra Equivalency Analysis
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5 DISCUSSION AND CONCLUSIONS
5.1 Key Observations and Findings
This analysis and associated research yielded a number of key observations:
The baseline level of capture efficiency and volume reduction provided by conventional
biofiltration BMPs, if effectively designed per Attachment H, is relatively high. This
establishes a relatively high baseline standard for Filterra systems to meet in providing
equivalent performance.
There is substantial leeway within the Attachment H criteria and local implementation
guidance that is expected to result in design variations of conventional biofiltration
throughout Los Angeles County. These variations are expected to result in fairly
important variations in hydrologic performance. Additionally, variations in operations
and maintenance conditions over time (i.e., decline in media rates, reduction in active
storage volume from sedimentation) are also expected to influence performance.
It is possible to design Filterra systems to match the capture efficiency of conventional
biofiltration BMPs. This requires larger sizes of Filterra systems than was required for
treatment control BMPs under the previous MS4 Permit. This also requires a
commitment to regular maintenance consistent with Filterra standard maintenance
requirements.
Filterra systems alone are not expected to match the volume reduction performance
provided by conventional biofiltration that is effectively designed, even in lined systems.
However, it is possible for Filterra systems to mitigate for deficiency in volume reduction
via either supplemental infiltration storage or increasing the size of Filterra systems to
increase their capture efficiency thereby providing equivalent load reductions.
For water that is treated and released, Filterra performance studies generally showed
similar or better concentration reduction compared to conventional biofiltration. Filterra
performance tended to be less variable in most cases. Filterra systems also did not exhibit
the potential for major nutrient export that is relatively common in conventional
biofiltration.
When studies from the International BMP Database were screened to best match
conventional biofiltration designs per Attachment H (specifically compost and sand
fractions), the treatment performance tended to decline somewhat. This is consistent with
findings related to use of compost in biofiltration media from other studies. This indicates
that there is still progress to be made in addressing nutrient export issues in conventional
biofiltration systems. For example, in Western Washington results of rigorous testing of
media comprised of sand and compost conforming to local specifications have led to
limitations on the use of biofiltration in nutrient sensitive watersheds and have stimulated
research into alternative media blends.
Overall, if Filterra systems are designed based on the methodology and criteria presented in
Section 4 and effectively operated and maintained these systems are expected to match or exceed
the performance of conventional biofiltration within a reasonable margin of uncertainty.
Filterra Equivalency Analysis
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5.2 Reliability and Limitations
There are a number of uncertainties that influence the reliability of the findings presented in this
report. These are addressed in the paragraphs below.
Modeled hydrologic performance estimates. Performance estimates were based on models
which were not calibrated. This introduces some uncertainty. This uncertainty was mitigated
by applying identical input parameters and modeling approaches for conventional
biofiltration and Filterra systems, as appropriate. This has the effect of offsetting the
majority of potential sources of bias.
Treatment performance estimates for conventional biofiltration. Treatment performance
estimates were based on peer reviewed studies from the International BMP Database and
other peer reviewed third party studies that were selected to be representative of the BMPs
being compared. Due to limited sample size of conventional biofiltration monitoring studies
and some deficiencies in documentation of these studies, it was not possible to quantitatively
evaluate whether performance estimates are specifically representative of Attachment H
biofiltration. Additionally, performance has been observed to vary greatly from site to site,
indicative of the importance of design factors such as sizing, media composition, sources of
media components, and other design factors. The screened and unscreened datasets analyzed
are believed to provide reliable information about the range of potential performance that
may be expected from conventional biofiltration in Los Angeles County; however they are
not intended to be used as a predictive tool for any one variation of biofiltration design.
Reliability of these data was improved through the application of robust statistical methods
that account for the influence of influent concentration and provide a quantification of
uncertainty.
Treatment performance estimates for Filterra systems. Filterra systems have been
evaluated in a range of sites and climates; however none of these sites were in Los Angeles
and not all studies are necessarily representative of the influent quality from typical Los
Angeles land uses. Additionally, the sample size of Filterra datasets is still somewhat low in
comparison to conventional biofiltration BMPs. These factors are mitigated to a large extent
by the standardized design that accounts for rainfall intensity/duration differences and
ensures consistency in media composition of Filterra systems. These factors improve the
transferability of findings between regions. Additionally, the reliability of Filterra
performance data was improved by applying the same robust statistical methods as used for
conventional biofiltration, which help adjust for differences in influent quality between
studies.
TSS removal as a surrogate for additional capture in lieu of volume reduction. For
small deficiencies in volume reduction, a TSS treatment removal rate of 80 percent was used
to calculate required additional capture efficiency in lieu of volume reduction. A multi-
parameter approach would be more complex and would need to account for the export of
nutrients in conventional biofiltration as well as the observation that metals performance
Filterra Equivalency Analysis
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tends to vary substantially with influent concentration (i.e., where influent concentration is
relatively low, the removal efficiency tends to be lower, but the resulting effluent
concentration is still below typical water quality standards). Given that this approach is only
intended to offset minor volume reduction (up to about 20%), this is considered to be a
reasonable approach.
Sensitivity to site conditions. The effectiveness of volume reduction processes is
particularly sensitive to estimates of site infiltration rate. It may not be possible to anticipate,
with certainty, what the final long term infiltration rate will be in the post construction
condition. This limitation is largely mitigated for the purpose of this analysis because the
uncertainty in infiltration rate influences the design and performance of conventional
biofiltration and Filterra with infiltration storage similarly. Additionally, estimating the site
infiltration rate is now a standard part of developing a BMP plan for a site, therefore
approaches for developing this estimate should improve in reliability with time. Finally,
both systems provide excellent TSS treatment prior to infiltration and long term infiltration
rates should therefore be more reliable.
Variability in design and construction process. The analyses and criteria presented in this
report are based on the assumption that the BMPs will be effectively designed and
constructed consistent with a typical standard of care. It is inherent that design of non-
proprietary conventional biofiltration BMP provides a greater degree of freedom and
associated professional judgment as part of preparing design calculations, design drawings,
and specifications. This introduces a wider potential range of resulting designs. Some may
be better than average, some may be worse. Additionally, there are typically a number of
specialized elements in the construction of a biofiltration BMP that may introduce
variability in as-built condition as a result of contractor preferences and/or quality control
issues. There are many examples of biofiltration facilities that have failed due to design and
construction issues. In comparison, there is likely to be substantially less variability in the
design and construction of Filterra system compared to biofiltration BMPs.
Sensitivity to operations and maintenance. Both types of systems are susceptible to
decline in performance over time. Neither system will work if they are not regularly and
effectively maintained. Filterra systems may be more susceptible to rapid clogging because
of their relatively small footprint. However, this is mitigated by Filterra having a standard
maintenance plan that has been informed by feedback from O&M of numerous facilities.
Overall, the analyses are believed to result in reliable design assumptions. Where substantial
uncertainties exist, the analyses and assumptions have tended to err on the side of estimating
somewhat higher performance for conventional biofiltration and somewhat lower performance
for Filterra systems, which likely results in more conservatism in Filterra equivalency sizing.
Filterra Equivalency Analysis
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6 REFERENCES
Americast, Inc. 2009a. Filterra® Flow Rate Longevity Verification Study. May 2009.
Americast, Inc. 2009b. Filterra® Long Term Field Performance Evaluation Report. April 2009.
ATR Associates. 2009. Technical Report Addendum. Additional Field Testing and Statistical
Analysis of the Filterra® Stormwater Bioretention Filtration System. Prepared for Americast,
Inc. by Richard Stanford, ATR Associates, Inc., Strasburg, Virginia. January 26, 2009.
Automated surface Observing System (ASOS). (2015). ftp://ftp.ncdc.noaa.gov/pub/data/asos-
fivemin/.
California Department of Water Resources (CDWR). (2015). California Irrigation Management
Information System (CIMIS). Website: http://www.cimis.water.ca.gov/.
David N., Lent, M., Leatherbarrow, J., Yee, D., and McKee, L. (2011). Bioretention Monitoring
at the Daly City Library. Final Report. Contribution No. 631. San Francisco Estuary Institute,
Oakland, California.
Davis, A. P. (2007). “Field Performance of Bioretention: Water Quality.” Environ. Eng. Sci.
2007, 24, 1048–1063.
Davis, A., Traver, R., Hunt, W., Lee, R., Brown, R., and Olsz ewski, J. (2012). ”Hydrologic
Performance of Bioretention Storm-Water Control Measures.” J. Hydrol. Eng., 17(5), 604–
614.
Gilbreath, A. N., Pearce, S. P. and McKee, L. J. (2012). Monitoring and Results for El Cerrito
Rain Gardens. Contribution No. 683. San Francisco Estuary Institute, Richmond, California.
Herrera (2009). Filterra Bioretention Filtration System Performance Monitoring Technical
Evaluation Report. Prepared for Americast, Inc. by Herrera Environmental Consultants, Inc.,
Seattle, Washington. December 3, 2009.
Herrera (2014a). Technical Evaluation Report: Filterra System Phosphorus Treatment and
Supplemental Basic Treatment Performance Monitoring. Prepared for: Americast, Inc. (as art
of TAPE Process) by Herrera Environmental Consultants, Inc., Seattle, Washington.
February 12, 2014
Herrera (2014b). Final Report: 185th Avenue NE Bioretention Stormwater Treatment System
Performance Monitoring. Prepared for City of Redmond, by Herrera Environmental
Consultants, Inc., Seattle, Washington. March 6, 2014.
Herrera (2015a). Interim Project Report: City of Redmond Six Bioretention Swales Monitoring.
Prepared for City of Redmond, by Herrera Environmental Consultants, Inc., Seattle,
Washington. February 20, 2015
Herrera (2015b). Analysis of Bioretention Soil Media for Improved Nitrogen, Phosphorous and
Copper Retention, Final Report, Prepared for Kitsap County by Herrera Environmental
Consultants, Seattle, WA, July 17, 2015.
Geosyntec Consultants and Wright Water Engineers (2009). Urban Stormwater BMP
Performance Monitoring. Prepared by Geosyntec Consultants and Wright Water Engineers,
Inc. Prepared under Support from U.S. Environmental Protection Agency, Water
Environment Research Foundation, Federal Highway Administration, Environmental and
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20
Water Resources Institute of the American Society of Civil Engineers. October 2009.
http://www.bmpdatabase.org/Docs/2009%20Stormwater%20BMP%20Monitoring%20Manu
al.pdf
Los Angeles County (LA County), 2000. Los Angeles County 1994-2000 Integrated Receiving
Water Impacts Report.
Los Angeles County (LA County), 2001. Los Angeles County 2000-2001 Stormwater
Monitoring Report.
Los Angeles County (LA County), 2006. Los Angeles County Hydrology Manual, Department
of Public Works (LACDPW), Alhambra, California
Larry Walker Associates and Geosyntec Consultants, 2011. Ventura County Technical Guidance
Manual for Stormwater Quality Control Measures. July 2011.
Leisenring, M., Poresky, A., Strecker, E., and M. Quigley, 2009. Evaluating Paired BMP
Influent and Effluent Data Using Running Bootstrap Medians. Proceedings of the American
Water Resources Association Annual Conference, Seattle WA, November 9-12, 2009.
Li, H. and Davis, A. (2009). ”Water Quality Improvement through Reductions of Pollutant
Loads Using Bioretention.” J. Environ. Eng., 135(8), 567–576.
National Climatic Data Center (NCDC). (2015). ftp://ftp.ncdc.noaa.gov/pub/data/hourly_precip-
3240/.
North Carolina State University 2015. Filterra Bioretention System Sediment Removal and
Hydrologic Performance Evaluation Report, Fayetteville Amtrak Filterra® Prepared for:
Filterra® Bioretention Systems. August 28, 2014. Prepared by Andrew Anderson and Andrea
Smolek.
Roseen, R.M. and Stone, R.M. (2013). Bioretention Water Quality Treatment Performance
Assessment. Technical Memorandum. Prepared for Seattle Public Utilities.
Singh, K. and Xie, M. (2008) Bootstrap: a statistical method. Rutgers University.
Yu and Stanford. 2006. Field Evaluation of the Filterra® Stormwater Bioretention Filtration
System. A Final Technical Report. Prepared for Americast, Inc. by Dr. Shaw L. Yu and
Richard L. Stanford, Department of Civil Engineering, University of Virginia. May 24, 2006.
Washington State Department of Ecology. 2014. 2012 Stormwater Management Manual for
Western Washington (as Amended in 2014. Publication Number 14-10-055.
.
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APPENDIX A – CONVENTIONAL BIOFILTRATION DESIGN ASSUMPTIONS FOR
PERFORMANCE MODELING
The following criteria from Attachment H were considered to be important for evaluating
pollutant load reduction performance of “conventional biofiltration” scenarios:
6 to 18-inch ponding area above media
Optional layer of mulch
2 to 3 feet of engineered filter media (2 feet typical) with a design infiltration rate of 5 to
12 inches/hour; the Attachment H specification calls for a mix of 60 to 80% fine sand and
20 to 40% compost
Gravel storage layer below the bioretention media to promote infiltration
Underdrain placed near the top of the gravel layer (or an infiltration sump otherwise
provided via an equivalent hydraulic control approach) in cases where underlying soil
infiltration rates allow
Underdrain discharge to the storm drain
Total physical water storage volume sized to be equal to at least the stormwater quality
design volume (SWQDv = runoff volume from the 85th percentile, 24-hour storm event)
Capacity (including stored and filtered water) adequate to biofilter 150 percent of the
portion of the SWQDv not reliably retained.
Within the bounds established by these criteria, a relatively wide range of actual biofiltration
designs could result as a function of site infiltration conditions as well as designer and local
jurisdiction preferences. An example of potential design variability is illustrated in Table A.1
below. For the purpose of this analysis, representative design assumptions were developed within
the range of potential design assumptions. These assumptions are also presented in Table A.1
with supporting rationales.
Table A.1 Biofiltration Design Assumptions from Various Sources and Selected Representative Design Assumptions
Design Assumption
Design References
Selected
Representative
Design Assumption
Rationale for Selected
Design Assumption
MS4 Permit
Attachment H
Los Angeles
County LID
Manual, static
method
Los Angeles
County LID
Manual, routing
method
City of Los
Angeles LID
Manual
Ventura
County TGM
Ponding Depth, ft 0.5 to 1.5 0.5 to 1.5 0.5 to 1.5 0.5 to 1.5 0.5 to 1.5 1.5
Many designers will utilize
deepest depth allowable
because of space efficiency.
Media Depth, ft 2 to 3 2 to 3 2 to 3 2 to 3 2 to 3 2
Typical design approach is to
use minimum depth due to
cost of media.
Gravel “sump” depth
below underdrain, ft
Not specified;
narrative
Not specified,
narrative
Not specified,
narrative
At least 1 feet;
up to 2 feet if
soils allow
incidental
infiltration
0.5 minimum
below
underdrain
Depth that would
drain in 24 hours.
For example, 1.5 ft
if site infiltration
rate estimated at just
less than 0.3 in/hr
Approach produces a
reasonable design that
considers infiltration rates;
Attachment H states that
volume infiltrated within 24
hours can be considered
retained.
Media Filtration Rate,
in/hr 5 to 12 5 to 12 5 to 12 5 to 12 1 to 12 (5) 5 Representative of long term
operation after some clogging
Allowable Routing
Period for
Biofiltration
Treatment, hrs
Not specified
Routing is not
part of simple
method
Allows routing
of 24-hour
design
hydrograph from
LA County
HydroCalc
model
3 hours, unless
using a routing
model
Depth up to
ponding depth
(1.5 ft) can be
considered
routed
6 hours1
Based on evaluation of storm
durations for events similar to
design event. See footnote 1.
Resulting Footprint
Factor at 0.3 in/hr
Infiltration Rate, in/hr
(% of impervious
area)
Not enough
information to
calculate
7.5% 1.4%
2.4% (1.4%
with routing
similar to LA
County)
2.8% 2.0% Calculated based on
assumptions.
Note: where a range of guidance is allowed, the bolded number indicates the value that was used in calculations. The design v alues were selected based on
developing the most economical and space-efficient design that meets the applicable criteria.
1 – The allowable routing period was estimated based on the typical storm duration associated with events similar to the 85 th percentile, 24-hour storm depth (1.0
inches at LAX). This was estimated in two ways. For days with precipitation totals between 0.9 and 1 .1 inches, the total number of hours with rainfall was
tabulated (average = 11 hours; 10th percentile = 6 hours). This does not consider dry periods between hours with rainfall, therefore is somewhat conservative in
estimating the period of time available for routing biofiltered water during a given day. For unique precipitation events, separated by 6 hour dry period (potentiall y
spanning across breaks in calendar days), with precipitation totals between 0.9 and 1.1 inches, the total storm durations wer e tabulated (average = 16 hours; 10th
percentile = 7 hours). Based on this analysis, a 6 hour routing period is considered to be defensible and conservative in estimating the amount of w ater that can be
routed through a biofiltration system during typical storm events similar to the design storm event.
APPENDIX B – SWMM MODELING METHODOLOGY AND ASSUMPTIONS
Equivalency Scenarios
The relative performance of Filterra systems and conventional biofiltration was compared under
the following climate and site conditions:
Climate (and associated precipitation and ET): Los Angeles
Land Use (and associated imperviousness and runoff quality): Multi-family Residential
Soil infiltration rate: 0, 0.01, 0.05, 0.15, and 0.3 inches per hour
A hypothetical 1-acre catchment was used for this analysis and was not varied.
For conventional biofiltration, the sizing and design criteria described in Appendix A were
followed.
For Filterra systems, all combinations of the following sizing criteria were evaluated for each
combination of climate and site conditions:
Design precipitation intensity: 10 sizing increments were evaluated between 0.1 and 0.8
inches per hour.
Catchment time of concentration: 5 increments were evaluated between 5 minutes and 30
minutes
Downstream retention storage volume: 5 increments were evaluated between 0% (absent)
and 50% of the runoff from the 85th percentile, 24-hour storm event.
Specific SWMM modeling representations of each combination of site conditions and BMP
parameters are described in this Appendix.
Overview of SWMM Analysis Framework
SWMM was used to estimate the long-term capture efficiency and volume reduction from
conventional biofiltration BMPs and Filterra systems for each scenario. SWMM
compartmentalizes its computations based on several physically-based processes including
surface runoff, evaporation, infiltration, and flow routing. A conceptual representation of the
SWMM model framework used for this analysis is provided in Figure B.1. Within this
framework, parameters were adjusted for each scenario to account for soil condition and BMP
sizing and design attributes.
In SWMM, subcatchment elements are used to generate a runoff hydrograph. Input data defining
the surface characteristics include subcatchment area, imperviousness, width, depression storage,
surface roughness, surface slope, and infiltration parameters. SWMM performs a mass balance
Filterra Equivalency Analysis
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of inflows and outflows to determine runoff from a subcatchment. The inflows to this mass
balance are precipitation and any runoff directed from another subcatchment. The outflows from
the mass balance include evaporation, infiltration, and runoff. The runoff parameters assumed for
this analysis are discussed in this Appendix.
A variety of hydraulic flow routing elements exist in SWMM, but fundamentally, the program
includes nodes (i.e., storage units, manholes, and outfalls) and links (i.e., conduits, pipes, pumps,
weirs, orifices, and outlets). Storage units were used in this equivalency analysis to represent the
storage and routing attributes of BMPs. The elements defining the storage volume and related
discharge were adjusted based on the various sizing and design criteria evaluated in the
equivalency scenarios, the details of which are discussed in this Appendix.
Figure B.1. Schematic SWMM modeling framework in support of equivalency analysis
SWMM was run in continuous simulation mode over a 15-year period (2000-2015). A
continuous hydrograph of runoff was generated and routed through the model representations of
BMPs. The results were tracked and reported in terms of long term runoff volume, long term
volume lost in the BMP, long term volume bypassing or overflowing the BMP, and long term
volume treated in the BMP. The 15-year period of record was selected based on the availability
of high quality 5-minute resolution precipitation data, which are important for representing urban
catchments with short time of concentration. To ensure comparability, the same forcing d ata
(rainfall, ET) were applied to conventional biofiltration scenarios and Filterra scenarios.
Filterra Equivalency Analysis
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Meteorological Inputs
Precipitation
Precipitation data utilized this study included continuous hourly precipitation data collected by
the National Climatic Data Center (NCDC) and five-minute precipitation data from the
Automated Surface Observation System (ASOS); both part of the National Oceanic and
Atmospheric Administration (NOAA). The hourly precipitation datasets from NCDC provided
an extensive record of precipitation data from 1948 through February 2015. NCDC precipitation
datasets at major airports are known to be of high quality with few areas of missing or
unreportable data and therefore were used as a quality standard to compare to the ASOS dataset
as well as the basis for estimating long term precipitation statistics. The ASOS dataset does not
receive the same level of quality review that the NCDC data and has considerably shorter period
of data (ASOS dataset is from 2000 to February 2015). However, the ASOS data is collected at
5-minute intervals, providing considerably better temporal resolution for precipitation when
modeling of urban BMPs, particularly for small catchments. Therefore, NCDC data were used to
define the 85th percentile 24-hour sizing criteria and to validate the ASOS data, while the ASOS
data was used as the input to comparative model simulations. The period of record of ASOS data
(15 years) is less than ideal for characterizing long term averages, however because the same
dataset was used for both conventional biofiltration and Filterra systems, this length if record is
ample to provide a valid comparison of performance.
The Los Angeles Airport location was included in this analysis (NCDC: 045114, ASOS:
KLAX). The 85th percentile 24-hour precipitation depth was determined using the entire length
of record at the NCDC gage and compared to the values produced from the ASOS gages (Table
B-1). In determining the 85th percentile, 24-hour depth, days with 0.1 inches or less were
excluded from both datasets. The resulting 85th percentile, 24-hour depths are well matched
between the NCDC and ASOS gage. Scatter plot comparisons of NCDC and ASOS datasets for
monthly and 24-hour totals at each location also show good agreement (Figure B-1 and Figure
B-2). This indicates that the ASOS data provide a reasonable estimate of absolute long term
performance in addition to providing a reliable comparison between BMP types.
Table B.1. Summary of 85th percentile 24-hour storm depths.
Storms Gage Location 85th Percentile 24-Hour
Depth (in)
All NCDC Storms > 0.1 inch
(1948-2015) Los Angeles Airport (045114) 1.01
All ASOS Storms > 0.1 inch
(2000-2015) Los Angeles Airport (KLAX) 0.96
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Figure B.2. Scatter plot comparisons of monthly (left) and daily (right) precipitation depths
for NCDC and ASOS datasets.
ET Parameters
Reference ET values for Zone 4 of the California Irrigation Management Information System
were used to estimate evaporation for all simulations (CDWR 2015). Zone 4 represents coastal
areas; actual ET may be higher in inland areas and is likely higher on average in Southern
California than the San Francisco Bay Area, however the influence of this assumption is minor
and will tend to cancel out in comparison between BMP types. Average ET conditions were
represented by setting the modeled evaporation values equal to 60% of the reference ET values
to represent a mix of urban conditions with varied plant pallets and shading conditions based on
guidance provided by CIMIS (CDWR 2015). The assumed ET values for this analysis are
presented in Table B.2.
Table B.2. Assumed ET values for all scenarios
Month Evapotranspiration Rates 60%
inch / day days / month inch / month inch / month
January 0.05 31 1.55 0.93
February 0.08 28 2.24 1.34
March 0.12 31 3.72 2.23
April 0.17 30 5.1 3.06
May 0.22 31 6.82 4.09
June 0.26 30 7.8 4.68
July 0.28 31 8.68 5.21
August 0.25 31 7.75 4.65
Filterra Equivalency Analysis
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Month Evapotranspiration Rates 60%
inch / day days / month inch / month inch / month
September 0.19 30 5.7 3.42
October 0.13 31 4.03 2.42
November 0.07 30 2.1 1.26
December 0.05 31 1.55 0.93
Total (year) 365 57.04 34.22
Runoff Parameters
The key SWMM parameters used to estimate surface runoff are subcatchment area, width,
imperviousness, depression storage, surface roughness, surface slope, and infiltration parameters.
The majority of surface characteristics were kept constant for both BMP systems and across all
land use types. The values assumed for each of these parameters are in Table B.3.
Imperviousness was varied for different land uses as described in the Ventura County Technical
Guidance Manual for Stormwater Quality Control Measures (Larry Walker Associates and
Geosyntec 2011) and is presented for each land use within Table B.3. Additionally, for Filterra
simulations, the width parameter (defines the overland flow length for runoff to travel), were
adjusted to reflect differences in time of concentrations. The values applied within the model
were estimated through an iterative process during the modeling phase.
Runoff estimation is affected by losses to infiltration processes over pervious areas of the
subcatchment. The Green-Ampt method of estimating infiltration was used to represent this
process. Three input parameters were used to characterize infiltration with this method: initial
deficit, saturated hydraulic conductivity, and suction head. These parameters represent surface
conditions and are not necessarily related to the saturated infiltration processes that may occur
below a BMP (typically several feet below the surface). Because the purpose of this equivalency
analysis was to isolate differences between two BMP types, the subcatchment infiltration
parameters were held fixed for all scenarios. Parameters were selected to represent typical urban
conditions with disturbed urban soils (Table B.3).
Table B.3. Summary of SWMM parameters to represent runoff parameters
SWMM Runoff
Parameters Units Values Source/Rationale
Wet time step seconds 150
Set to half the time steps of
precipitation input data (300
seconds)
Dry time step seconds 14,400 Equivalent to 4 hours.
Period of Record January 2000-December 2014 Availability of ASOS data
Filterra Equivalency Analysis
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SWMM Runoff
Parameters Units Values Source/Rationale
Percent of Impervious
Area percent Multifamily Residential = 74 Los Angeles County Hydrology
Manual (2006)
Impervious Manning’s
n unitless 0.012 James and James, 2000
Pervious Manning’s n unitless 0.15
James and James, 2000 (mix of
dense grass and mulched
landscaping)
Drainage area acres 1 Hypothetical for purpose of
analysis
Width feet
174 feet by default (equates to
250-ft path length)
For Filterra scenarios, variable to
represent different time of
concentrations
Typical assumption for urban
drainage patterns
Slopes ft/ft 0.03 (represents average of roofs,
landscaping, and streets) Professional judgment
Evaporation in /
month
60% of reference ET values
(Table B.4) CIMIS (CWDR, 2015)
Depression storage,
impervious inches 0.02 James and James, 2000
Depression storage,
pervious inches 0.06 James and James, 2000
Saturated Hydraulic
Conductivity (in/hr) in/hr 0.15 EPA SWMM User’s Manual for
typical disturbed urban soils
Initial Moisture Deficit
(in/in) in/in 0.29 EPA SWMM User’s Manual for
typical disturbed urban soils
Maximum Suction
Head (inches) inches 8 EPA SWMM User’s Manual for
typical disturbed urban soils
BMP Representation
Both the conventional biofiltration BMPs and Filterra systems were simulated using a storage
unit with outlets to represent infiltration losses (if present) and treated discharge, and a weir to
represent overflow/bypass. The elevations of these elements within the storage unit were used to
represent the design profiles of these systems. Storage compartments were broken into:
evaporation storage (i.e., water stored in soil that is not freely drained); infiltration storage (i.e.,
water stored below the lowest outlet that can either infiltration or ET only); and freely drained
storage (i.e., water that can drain through the underdrains of the system at a rate controlled by the
Filterra Equivalency Analysis
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media hydraulic conductivity). In some scenarios an additional storage unit was located
downstream of the Filterra BMP to represent additional retention storage.
Conventional Biofiltration
Sizing criteria for the conventional biofiltration system was based on the runoff from the 85th
percentile, 24-hour storm depth (1.0 for LAX). For each scenario, this depth was applied to the
catchment area and imperviousness to compute an estimated runoff volume. Storage profiles for
the conventional biofiltration system were established to represent typical profiles for
conventional biofiltration consistent with what is required by Attachment H of the MS4 Permit,
which are presented in Appendix A. The storage profiles included equivalent storage volumes
provided in the ponding depth, media depth (divided between ET storage and freely drained
storage), gravel layer, and placement of the underdrain system specific to the site conditions.
Based on the equivalent storage depth in these profiles and the design storm runoff volume, the
required footprints were calculated. For gravel, a porosity of 0.4 was assumed. For media, a
porosity of 0.4 in/in was assumed, divided as 0.15 in/in soil suction storage (i.e. ET storage) and
0.25 in/in freely drained storage. The profiles used for this analysis and the typical footprints are
presented in Table B.4.
For the purpose of estimating long term volume reduction and baseline capture efficiency, the
entire pore volume was assumed to be immediately available. However, because water takes
time to travel through the soil column, it is possible for a biofiltration BMP to overflow before
the entire soil poor volume is utilized. Based on analysis of flow monitoring data, Davis et al.
(2011) found that the volume immediately available within a storm is better represented by the
bowl volume (surface ponding) and the freely drained pores within the root zone (approximately
the top 1 foot of soil). To check whether this condition controlled, para llel model runs were
conducted where the storage volume equaled the bowl volume plus freely drained pores in the
soil root zone, and the drawdown time was adjusted for only this volume. The result was that this
condition reduced capture efficiency by approximately 2 percent. This indicates that this
condition controls performance relatively rarely, but is not negligible.
Filterra Equivalency Analysis
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Table B.4. Summary of conventional biofiltration profiles
Infiltration
Rate, in/hr
Retention
Sump
Depth (as
gravel
depth)1, ft
Effective
Water
Storage in
Retention
Sump (ft)
Media
Depth,
ft
Effective
Water
Storage
in
Media2,
ft
Ponding
Depth,
ft
Total
Effective
Water
Depth
(ft)
Approximate
Footprint
Sizing
Factor (Los
Angeles)3
0.3 1.5 0.60 2 0.8 1.5 2.9 1.5%
0.15 0.75 0.30 2 0.8 1.5 2.6 1.6%
0.05 0.25 0.10 2 0.8 1.5 2.4 1.7%
0.01 0.05 0.02 2 0.8 1.5 2.32 1.7%
0 0 0.00 2 0.8 1.5 2.3 1.8%
1 Sump storage was determined based on the depth of water that would infiltrate in 24 hours based on guidance
provided in Attachment H.
2 Media storage depth divided as 0.3 ft suction storage and 0.5 ft freely drained storage.
3 Expressed as BMP footprint as percent of tributary area ; Multi-family density of 74% impervious was used as a
representative value for simulations.
Filterra
An array of flow-based sizing increments were applied to define the physical dimensions of the
Filterra system to be modeled in each scenario. Ten increments of uniform design intensities
ranging from 0.1 inches/hour up to 0.8 inches/hour (0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5, 0.6,
0.8) were established to represent a range of potential Filterra sizing criteria to achieve
equivalency. For each scenario, the design intensity was applied to the catchment area and
imperviousness to calculate the runoff flowrate. The treatment capacity of the Filterra system
was set at 140 in/hr (or 0.0032 cu-ft/sec per sq-ft). Based on the required treatment flowrate and
the Filterra treatment capacity, the required Filterra footprint was determined.3 Similar to the
conventional biofiltration system, a vertical profile was also established as an input to the model,
including ponding depth, pore space in mulch and media, and underdrains (Table B.5). The
volume of the Filterra system is negligible; however the entire volume was assumed to be
available as a result of the very high infiltration rate of the Filterra media.
Further scenarios were developed for the Filterra system that included supplemental downstream
retention. These supplemental storage volumes were sized based on a percent age of the runoff
volume from the 85th percentile, 24-hour depth (0% (absent), 10%, 20%, 30%, 40%, 50%). For
these scenarios, an additional storage unit was simulated and received the treated flow from the
3 In practice, designers would select a standard Filterra size that meets or exceeds the required design flowrate,
therefore many systems will tend to be oversized in practice; the approach used for this equivalency analysis is
conservative in that it assumes exactly the minimum size is used.
Filterra Equivalency Analysis
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upstream Filterra storage unit. The profile of the Filterra system is described in Table B.5. The
downstream retention unit was modeled with an assumed depth of 2.1 feet, based on typical
Contech ChamberMaxx system geometry, assuming 6 inches gravel above and below the
ChamberMaxx units.
Table B.5. Summary of profile for Filterra systems
Media
Filtration
Rate,
in/hr
Gravel
Underdrain1,
ft
Effective
Water
Storage in
Retention
Sump (ft)
Media
Depth,
ft
Effective
Water
Storage
in
Media2,
ft
Ponding
Depth,
ft
Total
Effective
Water
Depth
(ft)
Approximate
Footprint
Sizing for
0.3 in/hr
scenario3
140 0.5 0.2 2 0.5 0.5 2.4 0.19%
1 Gravel layer based on typical Filterra design; all of the gravel layer was assumed to drain freely
to the underdrain
2 Media storage depth divided as 0.3 ft suction storage and 0.5 ft freely drained storage.
3 Expressed as BMP footprint as percent of tributary impervious area (varies by land use and
sizing increment; for example purposes only).
Filterra Equivalency Analysis
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APPENDIX C – DATASETS AND ANALYSIS METHODS FOR POLLUTANT
TREATMENT EVALUATION
Data Development and Analysis Framework
BMP performance is considered to be a function of BMP type, BMP design parameters, influent
water quality characteristics, and other factors. As part of this analysis, it was necessary to
develop a statistical description of BMP performance that accounted for the difference between
conventional biofiltration and Filterra systems and also accounted for the influence of land use
runoff quality (i.e., BMP influent quality) on the expected BMP performance. The data
development and analysis framework used for this project included four steps:
1) Compile and review data from monitoring studies of conventional bioretention systems;
then screen these studies to identify studies that are reasonably representative of
conventional biofiltration designs that would meet the MS4 Permit requirements,
particularly focusing on factors that would influence treated effluent quality.
2) Compile and review monitoring data from full-scale monitoring studies of Filterra
systems.
3) Apply a common statistical analysis framework to analyze the data from both datasets.
4) Determine representative land use runoff quality.
5) Based on results from step 3 and 4, estimate the effluent quality expected for
conventional biofiltration and Filterra systems for each pollutant for a range of land use
types.
Compilation and Screening of Conventional Biofiltration Studies
The International Stormwater BMP Database (www.bmpdatabase.org) includes storm event
monitoring data from 28 peer-reviewed studies of bioretention BMPs with underdrains. These
data were used as the primary source for characterizing the treatment performance of
conventional biofiltration BMPs in this study. In addition to the 28 studies from the International
BMP Database, four peer-reviewed research studies (Davis 2007; Li and Davis 2009; David et
al., 2011; Gilbreath et al. 2012) not contained in the International BMP Database were added to
the sample pool for analysis. Two of these studies were conducted recently in the San Francisco
Bay area, which has biofiltration design standards and media specifications nearly identical to
Attachment H of the Los Angeles MS4 Permit. The two other additional studies were included
due to their similarity to Attachment H design criteria and rigor of their analytical methods.
Screening Process for Developing Conventional Biofiltration Sample Pool
To our knowledge, there have yet to be any BMPs monitored in Southern California that have
been constructed to the specific criteria of Attachment H. Additionally, the two studies
monitored in the San Francisco Bay area (designed to very similar standards as Attachment H)
Filterra Equivalency Analysis
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(David et al., 2011; Gilbreath et al. 2012) provide a relatively small sample size and did not
monitor for nutrients. Therefore, it was necessary to broaden the scope of studies to represent
conventional biofiltration.
In general, the bioretention BMPs in the International BMP Database are considered to be
representative of the range of designs that could meet the MS4 Permit Attachment H
requirements. Most of the bioretention studies in the BMP Database were completed fairly
recently (most in the last 10 years) and have typically been designed, constructed, and/or
monitored under the supervision of experienced researchers. Many of these systems have been
designed with BMP profiles (i.e., ponding depth, media depth), media filtration rates, and media
composition that are similar to the criteria in Attachment H. However, where design attributes
indicated that performance would be expected to be poorer than Attachment H designs and/or
representativeness could not be evaluated, these studies were screened out of the analysis pool
for this study. Systems that were expected to achieve similar or better performance than a typical
BMP designed per Attachment H were kept in the pool; this is a conservative approach when
evaluating Filterra equivalency because it tends to establish a higher baseline for comparison
than if these BMPs were excluded.
Screening criteria were developed based on professional judgment, as informed by review of
literature and BMP performance studies. Our understanding of the influence of design
parameters on bioretention performance was informed by studies in the BMP Database (see
various summary reports at www.bmpdatabase.org), a recent evaluation by Roseen and Stone
(2013), and review of recent bioretention media research in Washington State. A summary of the
relevant findings are provided in the paragraphs below.
Roseen and Stone (2013) conducted an evaluation of biofiltration performance to determine how
design criteria and media composition influence performance. As part of their research, they
compiled site, design, and performance data for 80 field bioretention systems and 114 lab
columns/mesocosms. Data from the International BMP Database were included in this pool as
well as other research studies. Performance data were compiled as study summaries (e.g., study
median influent, effluent, and removal efficiency). Roseen and Stone then utilized design
information to categorizing systems into groups based on common combinations of factors. They
then conducted a statistical evaluation of how performance was influenced by design factors
such as presence/absence of mulch layers, use of compost in media, infiltration rate of media,
ratio of tributary to biofiltration area, presence/absence of pretreatment, presence/absence of
internal storage layers, etc. Roseen and Stone found that the presence of compost in mixes
strongly influences the variability in performance and potential export of pollutants, including
phosphorus, nitrogen, and copper. Systems without compost and/or with a high fraction of sand
tended to provide the most consistent and best performance for these pollutants. Systems with an
Filterra Equivalency Analysis
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internal water storage zone tended to perform better for nutrients than systems without an
internal water storage zone. Finally, they found that media flowrate and depth of media bed
tended to have an influence on performance. Beyond these findings, the influence of other
parameters was less conclusive.
Recent bioretention studies, many in Washington State (Herrera 2014b, 2015a, 2015b), have
identified the potential severity of pollutant export of nitrogen, phosphorus, and copper from
conventional biofiltration systems and have evaluated the potential sources of these issues. For
example, a full scale field monitoring stud y in the City of Redmond (WA) observed export of
nitrate on the scale of 100 mg/L higher than influent quality and dissolved copper on the scale of
10 to 20 ug/L higher than influent. Follow up research has shown that compost is consistently
associated with export of copper, nitrogen and phosphorus, even when the highest quality
compost products available are used in designs and at proportions as low as 10% of the media
blend by volume. This research also found that some sand products can also contain elevated
levels of phosphorus and copper. These studies are relevant because the standard biofiltration
media specifications for Western Washington are very similar to Attachment H, calling for 60 to
65 percent sand and 35 to 40 percent compost. It should also be noted that the compost
certification criteria in Washington State (Washington Department of Ecology, 2014) allow for
half as much metals content as allowed in the Attachment H specification, therefore should
theoretically have less potential for export of metals than compost meeting the Attachment H
specification.
Based on these literature findings and best professional judgment, the following criteria were
applied as part of screening bioretention studies:
Systems with media filtration rates substantially higher than 12 inches per hour were
excluded – while higher rate media has been found to provide good performance in some
cases, the general trends observed by Roseen and Stone (2013) indicated a decline in
performance for some parameters with increased infiltration rates.
Systems with sizing factors (BMP area as fraction of tributary area) substantially smaller
than the 3 to 5 percent (20:1 to 30:1 ratio of tributary area to BMP area) were excluded –
this parameter is related to media filtration rate and is an indicator of the degree of
hydraulic loading.
Systems that were observed to have very infrequent underdrain discharge (i.e., mostly
infiltration) were excluded – for these designs, the effluent that was sampled for water
quality was likely not representative of the entire storm event.
Systems with internal water storage zones were kept in the pool of data; these systems are
believed to provide better control of nutrients than systems without internal water
storage; Attachment H does not require internal water storage to be provided.
Filterra Equivalency Analysis
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Based on the findings of Roseen and Stone (2013) as well as recent research in
Washington State, mixes with less compost and a higher fraction of sand than the
Attachment H specification were kept in the sample pool because they are believed to
provide more reliable performance and less potential for export of pollutants on average
than a 70-30 sand/compost mix.
Systems that contained media with experimental components were excluded.
Finally, systems were excluded if there was not enough design information reported to be
able to evaluate representativeness, and/or any other factors were noted by the original
study researchers that were believed to contribute to poorer performance than average.
For example, some studies were noted as underperforming studies due to construction
issues, premature clogging, etc.
Overall, the screening that was applied is believed to improve the representativeness of the
sample pool and generally increase the average performance of the samp le pool compared to the
entire pool of studies contained in the International BMP Database. As discussed above,
establishing a higher baseline level of performance for conventional biofiltration is conservative
in the context of this evaluation.
Screening Results
Table C.2 summarizes the number of data points for each constituent after applying screening to
remove unrepresentative studies and without screening.
Table C.2. Summary of data points by parameter for conventional biofiltration BMPs
Constituent Number of Screened Data
Pairs
Number of Unscreened Data
Pairs
Total Suspended Solids 234 354
Total Phosphorus 242 384
Total Nitrogen 71 184
Total Copper 190 216
Total Zinc 200 252
Inventory of Bioretention Studies and Screening Results/Rationales
Table C.4 (located at the end of this Appendix) provides an inventory of studies of bioretention
with underdrains from the International BMP Database, screening results, and brief rationales for
screening.
Filterra Equivalency Analysis
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Compilation of Filterra Studies
Data were compiled from various field-scale Filterra monitoring studies from 2004 through
2014. The design of the Filterra system has not changed appreciably over time; therefore a
screening step to determine representative studies was not necessary. The studies used in thi s
analysis are summarized in Table 3 below. Full citations for these studies can be found in the
references section.
Table C.3. Inventory of studies and data points by parameter for Filterra systems
Pollutant (total
count of data
pairs)
Data Pairs
by Study Reference
Total Suspended
Solids
(n= 165)
11 TARP (2004-2005) : Yu and Stanford (2006)
7 TARP Addendum (2006-2007): ATR Associates (2009)
25 Perf. Over Time: Cal's Pizza (2008-2014): Americast (2009b; 2015)
24 Perf. Over Time: Jiffy Lube (2008-2011): Americast (2009b; 2015)
13 Perf. Over Time: Coliseum (2007-2014): Americast (2009b, 2015)
29 NCDNR Fayetteville (2013-14): NCSU (2015a)
22 TAPE Bellingham (2013): Herrera (2014a)
34 TAPE Port of Tacoma (2009): Herrera (2009)
Total Phosphorus
(n=146)
14 TARP (2004-2005) : Yu and Stanford (2006)
6 TARP Addendum (2006-2007): ATR Associates (2009)
71 Perf. Over Time: Cal's Pizza (2008-2014): Americast (2009b; 2015)
33 NCDNR Fayetteville (2013-14): NCSU (2015a)
22 TAPE Bellingham (2013): Herrera (2014a)
Total Nitrogen (n =
34) 34 NCDNR Fayetteville (2013-14): NCSU (2015a)
Total Copper
(n = 112)
8 TARP (2004-2005): Yu and Stanford (2006)
24 Perf. Over Time: Jiffy Lube (2008-2011): Americast (2009b; 2015)
21 Perf. Over Time: Coliseum (2007-2014): Americast (2009b, 2015)
13 NCDNR Fayetteville (2013-14): NCSU (2015a)
29 TAPE Port of Tacoma (2009): Herrera (2009)
17 TAPE Bellingham (2013): Herrera (2014a)
Filterra Equivalency Analysis
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Pollutant (total
count of data
pairs)
Data Pairs
by Study Reference
Total Zinc
(n = 120)
16 TARP (2004-2005): Yu and Stanford (2006)
24 Perf. Over Time: Jiffy Lube (2008-2011): Americast (2009b; 2015)
21 Perf. Over Time: Coliseum (2007-2014): Americast (2009b, 2015)
13 NCDNR Fayetteville (2013-14): NCSU (2015a)
29 TAPE Port of Tacoma (2009): Herrera (2009)
17 TAPE Bellingham (2013): Herrera (2014a)
Key to acronyms:
TARP: Technology Acceptance Reciprocity Partnership
TAPE: Technology Acceptance Protocol-Ecology (Washington State)
NCDNR: North Carolina Department of Natural Resources
NCSU: North Carolina State University
Data Analysis Method
The most common ways to characterize BMP performance include (1) removal efficiency
(percent removal) in various forms, and (2) effluent probability. In general, the effluent
probability approach is recommended for evaluating BMP performance and applying BMP
performance to pollutant load models (Geosyntec and Wright Water, 2009). This method
involves conducting a statistical comparison of influent and effluent quality to determine if
effluent is significantly different from influent. If effluent is significantly different from influent,
then the effluent quality is characterized by a statistical distribution developed from all effluent
data points. Probability plots are prepared indicating the probability that a certain effluent quality
is achieved.
However, to isolate differences in performance between two BMP types, the effluent probability
method requires the assumption that the influent quality was similar between the studies of the
two BMP types being compared. This assumption is generally reliable for categorical analysis of
BMPs in the International BMP Database because of the large number of studies in the most
categories in the Database. However, when comparing BMP types with a relatively limited
number of study sites (such as the Filterra dataset), this assumption may not be reliable.
To address these challenges and help ensure a valid comparison between conventional
biofiltration and Filterra systems, a moving bootstrap method (Leisenring et al., 2009) was
applied to both datasets. This method characterizes influent-effluent relationships such that the
BMPs compared do not need to have been studied under conditions with similar influent quality.
In this approach, all data pairs are used to form the total sample population. Then for each
increment of influent quality, a subsample of the overall population is formed including only
those data pairs that lie within a certain span of the selected influent quality. Applying bootstrap
Filterra Equivalency Analysis
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principles (Singh and Xie, 2008), the median and the confidence interval around the median is
computed as well the mean and the confidence interval around the mean. Then a new increment
of influent quality is selected and the process is repeated with a new subsample population until a
statistical description of effluent quality has been developed for each increment of influent
quality over the range of the data. Rules are also imposed regarding selection the initial span of
the moving window and expansion the span of the window, if needed, to ensure monotonicity
(i.e., ensure that effluent quality always increases or stays the same with increasing influent
quality).
Resulting tables and plots from this analysis are presented in Appendix D.
Land Use Stormwater Quality Inputs and Assumptions
Representative stormwater runoff concentrations for the land use condition used in this analysis
were developed based on the land use stormwater quality monitoring data reported in the Los
Angeles County 1994-2000 Integrated Receiving Water Impacts Report, 2000 and Los Angeles
County 2000-2001 Stormwater Monitoring Report, 2001(LA County 2000; LA County 2001).
The median and mean runoff quality values from this dataset were used as representative influent
water quality conditions for the purpose of evaluating BMP performance. These concentrations
represent only one land use monitoring station in one geographic area; actual conditions for a
given drainage area in a given region are anticipated to vary. Beyond the range of water quality
presented in this table, this analysis did not attempt to characterize the uncertainty/variability in
runoff water quality. This simplification is considered appropriate for evaluating equivalency in
BMP performance.
Land use runoff quality is reported in Appendix D.
Filterra Equivalency Analysis
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Table C.4. Inventory of conventional biofiltration studies from the International BMP Database and screening
rationale
Source Site Name Sponsoring Entity
State
City
Selected? Selection/Rejection Reasons
Int. BMP
Database
Rocky Mount
Grassed
Bioretention Cell 1
North Carolina State NC Rocky Mount Yes
Aligns with Att. H; Has
internal water storage zone
and underdrain
Int. BMP
Database
Rocky Mount
Mulch/Shrub
Bioretention Cell 1
North Carolina State NC Rocky Mount Yes
Aligns with Att. H; Has
internal water storage zone
and underdrain
Int. BMP
Database CHS_BioFilter The Thomas Jefferson Planning
District Commission VA Charlottesville Yes
Aligns with Att. H; Has
internal water storage zone,
underdrain, and mulch layer
(0.25 feet)
Int. BMP
Database
Parks & Forestry
Bioretention City of Overland Park KS Overland Park Yes
Aligns with Att. H; Has
internal water storage zone,
underdrain, and mulch layer
Int. BMP
Database Bioretention 6 Johnson County KS Shawnee Yes
Aligns with Att. H; Has
internal water storage zone
and underdrain
Int. BMP
Database G2 North Carolina State NC Greensboro Yes
Aligns with Att. H; Has
underdrain, and mulch layer
(7-10 cm)
Int. BMP
Database G1 North Carolina State NC Greensboro Yes
Aligns with Att. H; Has
underdrain, and mulch layer
(7-10 cm)
Int. BMP
Database L1 North Carolina State NC Louisburg Yes Aligns with Att. H;
Appropriate loading ratio
Int. BMP
Database Bioretention 3B Johnson County KS Shawnee Yes
Aligns with Att. H; Has
internal water storage zone
and underdrain
Int. BMP
Database
Parking Lot
Bioretention Cell City of Fort Collins CO Fort Collins Yes
Aligns with Att. H; Has
internal water storage zone
and mulch layer
Filterra Equivalency Analysis
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Source Site Name Sponsoring Entity
State
City
Selected? Selection/Rejection Reasons
Int. BMP
Database Bioretention Cells Johnson County SMP KS Overland Park Yes
Aligns with Att. H; Has
internal water storage zone,
underdrain, and mulch layer
Int. BMP
Database Bioretention Cell Johnson County SMP KS Overland Park Yes
Aligns with Att. H; Has
internal water storage zone
and underdrain
Int. BMP
Database
Bioretention
System (D1)
UNH/Cooperative Institute for
Coastal and Estuarine
Environmental Technology
NH Durham Yes
Aligns with Att. H; Has
pretreatment, internal water
storage zone, underdrain, and
mulch layer
Int. BMP
Database
UDFCD Rain
Garden
Urban Drainage and Flood
Control District CO Lakewood Yes
Aligns with Att. H; Has
internal water storage zone,
underdrain, and compost
layer
Int. BMP
Database
Hal Marshall
Bioretention Cell
City of Charlotte, North
Carolina NC Charlotte Yes Aligns with Att. H; Has
underdrain, and mulch layer
Int. BMP
Database
Rocky Mount
Grassed
Bioretention Cell 2
The Cooperative Institute for
Coastal and Estuarine
Environmental Technology
NC Rocky
Mountain Yes
Aligns with Att. H; Has
internal water storage zone
and underdrain
Li and
Davis
(2009)
Bioretention Cell 1
Prince George's County
Department of Environmental
Resources/ U of MD
MD College Park Yes Aligns with Att. H
Li and
Davis
(2009)
Bioretention Cell 2
Prince George's County
Department of Environmental
Resources/U of MD
MD Silver Spring Yes Aligns with Att. H
Davis
(2007) Bioretention Cell 1
Prince George's County
Department of Environmental
Resources/U of MD
MD College Park Yes Aligns with Att. H
David et al.
(2011)
Daly City Library
Rain Gardens San Francisco Estuary Institute CA Daly City Yes Aligns with Att. H
Gilbreath
et al. (2012)
San Pablo Ave
Green Streets San Francisco Estuary Institute CA El Cerrito Yes Aligns with Att. H
Int. BMP
Database Bioretention Area Virginia Department of
Conservation and Recreation VA Charlottesville No Not enough design info
provided
Int. BMP
Database Small Cell North Carolina Department of
Transportation NC Knightdale No Infiltration rate low; noted to
be underperforming BMP by
Filterra Equivalency Analysis
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Source Site Name Sponsoring Entity
State
City
Selected? Selection/Rejection Reasons
study researchers
Int. BMP
Database BRC_B North Carolina State NC Nashville No Infiltration too low and
undersized
Int. BMP
Database North cell North Carolina State NC Raleigh No Media very different from
Att. H
Int. BMP
Database
WA Ecology
Embankment at
SR 167 MP 16.4
Washington State Dept. of
Transportation WA Olympia No
Linear design; lateral flow;
not representative of typical
biofiltration design
Int. BMP
Database Bioretention Cell Delaware Department of
Transportation DE Dover No Design is very different from
Att. H
Int. BMP
Database East 44th St. Pond City of Tacoma WA Tacoma No No design data
Int. BMP
Database Tree Filter
UNH/Cooperative Institute for
Coastal and Estuarine
Environmental Technology
NH Durham No Design is very different from
Att. H
Int. BMP
Database BRC_A North Carolina State University NC Raleigh No
Infiltration rate very low;
noted to be a partially
clogged/failing system
Int. BMP
Database
Cub_Run_Biorete
ntion Fairfax County VA Fairfax No No design data provided
Int. BMP
Database South cell North Carolina State University
(BAE) NC Raleigh No Design is very different from
Att. H
Int. BMP
Database R Street City of Tacoma WA Tacoma No No design data provided
Filterra Equivalency Analysis
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APPENDIX D – RESULTS OF POLLUTANT TREATMENT DATA ANALYSIS
The data analysis methods described in Appendix C were applied to the datasets described in
Appendix C. The following pages present tabular and graphical results of this analysis.
Table D.1. Summary Statistics - Bioretention Studies and Filterra Studies
Median Statistics
Median 95th percentile UCL on
Median Median 95th percentile UCL on
Median Median 95th percentile UCL on
Median
TSS mg/L 53 12 13.7 11 12 4.9 5
Total Phosphorus mg/L 0.27 0.46 0.55 0.26 0.37 0.06 0.08
Total Nitrogen mg/L 2.3 1.6 2.9 1.19 1.52 1 1.6
Copper ug/L 22 12 15 12 14 10 10
Zinc ug/L 192 35 44 36 40 70 77
TSS mg/L 61 12 15 12 13 5.0 5.0
Total Phosphorus mg/L 0.32 0.47 0.55 0.28 0.43 0.09 0.11
Total Nitrogen mg/L 2 1.6 2.9 1.2 1.5 1 1.6
Copper ug/L 11 5.3 5.9 5.3 6.4 5.5 6.0
Zinc ug/L 66 20 27 18 26 31 35
TSS mg/L 129 16 18 16 18 5.2 7.0
Total Phosphorus mg/L 0.3 0.47 0.55 0.27 0.42 0.09 0.11
Total Nitrogen mg/L 2.4 1.6 2.9 1.2 1.5 1.3 1.6
Copper ug/L 21 12 15 12 13.85 10 10
Zinc ug/L 366 35 44 36 40 80 95
TSS mg/L 24 10.8 12.5 9.9 9.9 3 3
Total Phosphorus mg/L 0.14 0.39 0.45 0.21 0.25 0.04 0.05
Total Nitrogen mg/L 1.5 1.6 2.9 1.2 1.5 0.9 1
Copper ug/L 12 5.6 6.1 5.6 6.6 5.5 6.0
Zinc ug/L 89 20 27 18 26 35 37
Mean Statistics
Mean 95th percentile UCL on Mean Mean 95th percentile UCL on Mean Mean 95th percentile UCL on Mean
TSS mg/L 66 28 49 25 39 6.0 7.9
Total Phosphorus mg/L 0.39 0.80 1.3 0.65 1.0 0.11 0.14
Total Nitrogen mg/L 3.6 2.9 4.3 2.1 2.8 NA NA
Copper ug/L 39 19 29 16 24 18 29
Zinc ug/L 241 65 145 59 108 69 105
TSS mg/L 95 28 49 25 39 6.0 8.5
Total Phosphorus mg/L 0.39 0.80 1.3 0.65 1.0 0.11 0.14
Total Nitrogen mg/L 3.0 2.9 4.3 2.1 2.8 NA NA
Copper ug/L 15 13 21 13 19 12 19
Zinc ug/L 79 33 50 32 46 28 45
TSS mg/L 240 46 105 40 87 16 31
Total Phosphorus mg/L 0.41 0.80 1.3 0.65 1.0 0.11 0.14
Total Nitrogen mg/L 3.1 2.9 4.3 2.1 2.8 NA NA
Copper ug/L 32 19 29 16 24 18 29
Zinc ug/L 639 NA NA 59 108 168 285
TSS mg/L 46 18 28 18 27 6.0 7.9
Total Phosphorus mg/L 0.2 0.8 1.3 0.6 1.0 0.06 0.07
Total Nitrogen mg/L 2.1 2.9 4.3 2.1 2.8 1.1 1.5
Copper ug/L 12 10 15 9 14 9 15
Zinc ug/L 146 45 90 32 46 38 60
NA - Average values could not be computed for because the land use average influent is outside of the range of influent observed in monitoring studies.
Key to cell formatting
Red bold indicates median or mean effluent concentration higher than influent concentration. This is indicative of the potential for pollutant export.
Blue indicates upper confidence interval of effluent concentration is higher than the influent concentration. This is not a conclusive indicator, but is provided for reference.
Pollutant Units Median Representative
Runoff Quality
Conventional Biofiltration Effluent (Screened)Filterra EffluentConventional Biofiltration Effluent (Unscreened)
Commercial
High Density Single
Family Residential
Light Industrial
Multi-family
Residential
Land Use
High Density Single
Family Residential
Light Industrial
Multi-family
Residential
Conventional Biofiltration Effluent (Screened)Filterra Effluent
Commercial
Land Use Pollutant Units Mean Representative
Runoff Quality
Conventional Biofiltration Effluent (Unscreened)
Figure D.1 Moving Window Plots of Medians
Screened Biofiltration Dataset Unscreened Biofiltration Dataset Filterra Dataset
Figure D.1 Moving Window Plots of Medians
Screened Biofiltration Dataset Unscreened Biofiltration Dataset Filterra Dataset
Figure D.2 Moving Window Plots of Means
Screened Biofiltration Dataset Unscreened Biofiltration Dataset Filterra Dataset
Figure D.2 Moving Window Plots of Means
Screened Biofiltration Dataset Unscreened Biofiltration Dataset Filterra Dataset
WHITE PAPER
Filterra® Bioretention Systems:
Technical Basis for High Flow Rate
Treatment and Evaluation of Stormwater
Quality Performance
Prepared for
Contech Engineered Solutions, LLC
9025 Centre Pointe Drive
West Chester, OH 45069
Telephone: 1-800-338-1122
Prepared by
John Lenth and Rebecca Dugopolski
Herrera Environmental Consultants
2200 Sixth Avenue, Suite 1100
Seattle, Washington 98121
Telephone: 206.441.9080
Marcus Quigley, Aaron Poresky, and Marc Leisenring
Geosyntec Consultants
1330 Beacon Street, Suite 317
Brookline, Massachusetts 02446
Telephone: 617.734.4436
September 20, 2010
Filterra® Bioretention Systems: Technical Basis for
High Flow Rate Treatment and Evaluation of Stormwater Quality Performance
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Abstract
Media flow rate is one of many variables that influence the performance of
bioretention systems. While conventional thinking is that bioretention systems
with lower media flow rates provide better pollutant removal, a review of
scientific principles and monitoring data suggests otherwise. Based on a review of
scientific principles, the Filterra® Bioretention Stormwater Treatment System is
expected to be capable of achieving pollutant removal efficiencies and system
longevity on par with conventional slow flow rate bioretention systems. A review
of monitoring data demonstrates that Filterra® systems are capable of achieving
higher pollutant removal efficiency ratios and lower effluent concentrations, on
average, compared to similar categories of non-proprietary stormwater treatment
best managements practices (BMPs). In addition, Filterra® systems showed
statistically significant removals for a broader range of pollutants than similar
classes of non-proprietary BMPs. Finally, hydraulic performance data
demonstrate sustained high media flowrates in Filterra® systems over a variety of
ages. Overall, this paper finds that incorporation of a specialized media that can
efficiently treat stormwater at a high flow rate while supporting biological
processes within a relatively small footprint makes the Filterra® Bioretention
System an effective tool based on low impact development (LID) principles.
Filterra® Bioretention Systems: Technical Basis for
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1. Executive Summary
Conventional thinking is that slow flow rate bioretention media works better than high flow rate
bioretention media to remove pollutants from stormwater; however, an understanding of the
pollutant removal mechanisms of bioretention systems and analysis of water quality data
collected from high flow rate systems demonstrates that this is not the case. In addition, the
common use of high flow rate media and natural high flow systems for both water and
wastewater treatment provides long standing empirical evidence of the effectiveness of these
types of systems.
The dominant unit treatment processes provided by bioretention systems occur predominantly
during storm events and consist of inert and reactive filtration. A review of the scientific
principles behind these mechanisms suggests that high flow rate bioretention media would not
necessarily achieve significantly lower removal of particulate-bound and dissolved constituents
than low flow rate media. Processes occurring between storm events are also critical for the
retention of captured pollutants and the preservation or regeneration of hydraulic capacity and
the function of the dominant treatment mechanisms. Inter-storm processes, including
microbially-mediated transformations, biological uptake and sequestration, volatilization,
bacterial inactivation processes, soil processes, and routine maintenance, do not vary
significantly between high flow rate and slow flow rate bioretention systems. The Filterra®
Bioretention S ystem (Filterra® system) is designed to promote the within-storm and inter-storm
treatment processes characteristic of bioretention systems through the incorporation of mulch,
specialized media, and biologically active components. Based on a review of scientific
principles, the Filterra® system is expected to be capable of achieving pollutant removal
efficiencies and system longevity on par with conventional slow flow rate bioretention systems.
Third-party analyses of the Filterra® system have demonstrated sustained high media flow rates
and treatment performance. Laboratory scale testing results support media filtration rates of
greater than 100 inches per hour. Results from field scale testing of hydraulic function of systems
of a variety of ages support the current design flow rate recommendation of 100 to 140 inches
per hour. Field scale testing of treatment performance has demonstrated variable, but generally
high and sustained performance. Results from five field studies were fairly consistent for total
suspended solids (TSS) with efficiency ratios ranging from 83 to 88 percent. The efficiency ratio
for total phosphorus had a much wider range from 9 to 70 percent, across five studies; the low
end of this range was due to low total phosphorus concentrations and high fractions of soluble
reactive phosphorus measured during one study. Total Kjeldahl nitrogen (TKN) had an
efficiency ratio of 40 percent in one study. The efficiency ratio for total copper ranged from 33 to
77 percent in three studies, while dissolved copper had an efficiency ratio of 48 percent in one
study. The efficiency ratio for total zinc removal ranged from 48 to 79 percent in three studies,
while dissolved zinc had an efficiency ratio of 55 percent in one study. The oil and grease
efficiency ratio was lower than expected (59 percent) due to low influent concentrations near the
detection limit in one study; however, the total petroleum hydrocarbon (TPH) efficiency ratio
was 96 percent in a different study.
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Effluent concentrations achieved in the full-scale studies were generally equal to or lower than
median effluent concentrations for the biofilter and media filter classes of best management
practices (BMPs) reported in the International Stormwater BMP Database. In addition, Filterra®
systems showed statistically significant removals for a broader range of pollutants than were
shown for the biofilter and media filter categories in the International Stormwater BMP
Database.
In summary, the Filterra® Bioretention System incorporates a specialized media that can treat
stormwater at a high flow rate to provide pollutant removal capabilities using a relatively small
footprint compared to slow flow rate bioretention systems. These design characteristics make the
Filterra® system a well-suited BMP, designed based on low impact development (LID)
principles, for a wide variety of conditions, allowing pollutant loads to be addressed close to
their source even on space-constrained sites where the use of traditional slow flow rate systems
would be problematic or infeasible. The Filterra® system also supports inter-storm processes that
work to preserve and restore treatment capacity and hydraulic function. These processes are
believed to help preserve the longevity of the system and reduce the need for major maintenance
and media replacement.
2. Introduction
Conventional thinking is that slow flow rate bioretention media works better than high flow rate
bioretention media to remove pollutants from stormwater; however, an understanding of the
pollutant removal mechanisms of bioretention systems and analysis of water quality data
collected from high flow rate systems demonstrates that this is not necessarily the case. This
paper discusses the pollutant removal mechanisms and presents the technical basis to
demonstrate the effectiveness of high flow rate media used in the Filterra® Bioretention
Stormwater Treatment System (Filterra® system) developed by Americast, Inc.
Similar to rain gardens and planter boxes, the Filterra® system design is based on bioretention
and LID principles. Bioretention technologies operate similarly to media filters (e.g., sand or
organic/sand filters) in terms of particulate removal and sorption of reactive constituents.
Additional unit treatment processes inherent to bioretention designs include microbially-
mediated transformations, biological uptake, evapotranspiration, and other processes associated
with the vegetation and root structure. A key difference between bioretention systems and
biologically inactive media filtration systems is the contribution of these biological processes to
the retention and sequestration of captured pollutants and preservation and regeneration of
hydraulic function and pollutant removal capacity; therefore, bioretention systems can be
considered a sustainable design.
Bioretention technology design ranges from conventional bioretention media facilities (with
large unit storage volumes and a relatively slow filtration rate) to specialized media facilities
(with small unit storage volumes and a high filtration rate). Filterra® systems lie near the latter
end of this continuum by treating stormwater near its source, filtering stormwater at a high rate,
Filterra® Bioretention Systems: Technical Basis for
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allowing for a small footprint, and providing a standardized, easily installed and maintained
design. Specialized media in the Filterra® system is designed to optimize both a high flow rate
and the treatment capacity of the system. Inter-storm processes help to maintain these higher
flow rates and partially regenerate the pollutant removal capacity of the media. High flow rate
media and natural high flow systems are commonly used in both water and wastewater treatment
(Crites and Tchobanoglous 1998).
Section 3 of this white paper discusses treatment processes inherent to bioretention systems, with
a specific discussion of how media flow rates are expected to affect system performance. The
unit treatment mechanisms provided by Filterra® systems are discussed in Section 4.1, and a
summary of laboratory and field-scale evaluations of Filterra® system performance are provided
in Sections 4.2, and 4.3, respectively. Results from flow rate longevity studies and
recommendations for system maintenance are provided in Section 4.4.
3. Review of Unit Treatment Processes Provided by Bioretention
Systems
3.1 The Unit Treatment Process Approach
The unit treatment process approach to stormwater BMP selection and design is a widely
accepted approach that explicitly considers the characteristics of the pollutants of concern to
identify effective removal mechanisms that target those pollutants. The stormwater treatment
system is then designed to include components that provide the identified removal mechanisms.
This approach has been recommended in stormwater guidance documents published by respected
national research organizations (WERF 2005; NCHRP 2006) and is recognized as a robust
approach for BMP selection and design.
Bioretention systems provide numerous removal mechanisms to address a variety of stormwater
pollutants. For the purposes of this white paper, the key unit treatment processes provided by
bioretention areas are classified as within-storm treatment processes and inter-storm treatment
processes:
Within-storm treatment processes act on stormwater as it fills the bioretention
system, flows through the system, and is drawn down after the event. Most
bioretention systems are designed to:
1. Process a significant volume of water during an event
2. Draw down the remaining volume relatively quickly following an event
3. Retain little water between events
Therefore, within-storm processes are considered the most important for the
removal of pollutants from stormwater; the bulk of load reductions occur as
stormwater is briefly retained on the vegetated surface and then passed through
the underlying porous media to the bioretention system underdrains or to the
underlying native soils.
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Inter-storm treatment processes act on water and pollutants remaining in the
bioretention system (i.e., within soil pore spaces) for days, weeks, or months
between storm events. Inter-storm treatment processes do not provide a
significant direct contribution to pollutant removal due to the relatively small
volume of water retained within media pore spaces after an event, but are critical
for the retention of captured pollutants and the preservation or regeneration of
within-storm treatment mechanisms. For example, mechanisms like microbially-
mediated transformations and biological uptake can stabilize pollutants and
regenerate sorption sites.
Bioretention systems provide the following key pollutant removal mechanisms:
Within-storm Treatment Processes Inter-storm Treatment Processes
Inert Filtration (including surface sedimentation)
Reactive Filtration
Microbially-mediated Transformations
Biological Uptake and Sequestration
Volatilization
Bacterial Inactivation Processes
Soil Processes
Routine Maintenance
In addition to the efficiency of a BMP in removing of pollutants from treated water, the overall
effectiveness of a BMP in reducing pollutant loads is a function of the percentage of the long
term stormwater runoff volume that the BMP captures and treats (i.e., the capture efficiency),
and percentage of this volume that is lost to infiltration and evapotranspiration and is not
discharged (i.e., volume reduction). Capture efficiency is dependent on runoff patterns, the
storage volume of the BMP, the rate at which water is processed during a storm event, and the
rate at which the stored water is drawn down after an event. Bioretention systems with higher
media flow rates can achieve relatively high capture efficiency in smaller footprints, while
bioretention systems with slower flow rates generally require more storage volume and a
larger footprint to achieve the same capture efficiency. Volume reduction is a function of the
surface area of the BMP, the infiltration rate of underlying soils, depth to groundwater, the
moisture retention capacity of the media, and the evapotranspiration rates during the periods
between storm events. For bioretention systems without an impermeable liner, volume loss to
infiltration can be an important mechanism for removal of pollutant loads; volume losses to
evapotranspiration tend to be relatively minor for both lined and unlined bioretention systems.
3.2 Within-storm Treatment Processes
As mentioned above, within-storm treatment processes for bioretention systems primarily
include those that are associated with surface detention and filtration. For the purpose of
discussion, removal mechanisms are divided into two types of filtration:
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1. Inert filtration: filtration components that remove particulate-bound pollutants
through physical processes (e.g., straining); sedimentation at the surface of a filter
bed is considered to be a component of inert filtration
2. Reactive filtration: filtration components that remove dissolved and colloidal
pollutants through chemical or biological processes
The following sections describe these processes as they apply to conventional and high flow rate
bioretention systems.
3.2.1 Inert Filtration
Inert filtration involves six distinct mechanisms (Metcalf and Eddy 2003):
1. Straining – surficial straining or chance contact within the filter
2. Sedimentation – particles settle on the filtering medium within the filter
3. Impaction – heavy particles cannot follow the flow streamlines
4. Interception – particles following streamlines are removed upon contact with
media surfaces
5. Adhesion – particles become attached to surfaces as they pass by
6. Flocculation – large particles overtake small particles and join them to form
larger particles
Inert filtration is the dominant treatment mechanism for particulate-bound pollutants in
bioretention systems where removal is primarily accomplished by sedimentation and retention of
particles near the surface via surface straining, cake filtration, and shallow depth filtration.
Surface straining is the retention of particles larger than the pore size at the surface of the media
bed. Cake filtration occurs after particles have accumulated on the surface and this “cake” layer
begins to control the filtration process. Depth filtration retains small particles that are unable to
follow the convoluted paths through the media, where removal is primarily caused by
electrostatic attraction of particles to media, and micro-settling when laminar zones around the
media particles are formed.
Vegetation and mulch at the surface of bioretention systems also play an important role in inert
filtration processes by helping to promote localized settling and inhibiting the re-suspension of
settled pollutants. The roots and stems of plants also help keep soils open for infiltration,
effectively counteracting clogging mechanisms associated with filtration.
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For poorly-graded media beds (i.e., uniformly-graded sand), the ability of inert filtration to retain
a specific particle size is primarily a function of filter media particle size and bed depth. As a
general rule, when the median particle size of the influent is greater than one-tenth the median
particle size of the media, surface filtration (also known as cake filtration) will dominate
(Sansalone and Teng 2004; Teng and Sansalone 2004). Depth filtration also occurs for smaller
particles, but as influent particles become very small relative to the median particle size of the
media, mechanical filtration is no longer effective and sorption processes tend to dominate.
The depth of the media bed becomes a critical design factor when depth filtration and sorption
processes dominate. However, depths greater than 24 inches are typically not needed to achieve
high sediment removal in granular media filters (Crites and Tchabanoglous 1998). Further, the
top layer of the soil column represents the biologically active zone in which much of the
microbial, animal, and plant activity takes place.
Table 1 summarizes the dominant filtration mechanism by median diameter of the media
(D50media) and median diameter of the influent particles (D50influent).
Table 1. Dominant filtration mechanism based on media and influent particle size.
Condition Dominant Removal Mechanisms for Particles
D50media / D50influent < 10 Surface filtration (cake filtration)
10 < D50media / D50 influent < 20 Depth filtration of particulates
D50media / D50 influent > 20 Physical sorption of colloidal particulates
Source: Sansalone and Teng (2004)
D50media is the median diameter of the media (by mass).
D50influent is the median diameter of the influent particles (by mass).
Based on the classical model of a uniformly-graded media bed filter developed by O’Melia and
Ali (1978), permeability is inversely proportional to the square of the specific surface area of the
filter (internal surface area per bed volume). Because the internal surface area decreases as the
media particle size increases, larger media particle sizes are required to increase the treatment
flow rate. As shown by the relationships presented in Table 1, an increase in media particle size
would tend to result in less removal by cake filtration, and more removal by depth filtration for a
given stormwater particle size distribution. Thus, an increase in media particle size requires an
increase in bed depth to achieve equivalent particle removal performance (Yao 1971). However,
Johnson et al. (2003) found that particle removal within various media filters did not increase as
contact times increased beyond about 3 minutes.
While the classical model is useful in understanding filtration concepts, bioretention systems
may behave differently. Bioretention media beds are not commonly designed to utilize the
full depth of filtration. Media bed depth is typically selected to provide sufficient contact time
for reactive filtration processes rather than to provide greater depth for inert bed filtration.
Li and Davis (2008) found that TSS particles typically will not penetrate beyond the first 2 to
8 inches (5 to 20 centimeters) of bioretention media. By comparison, bioretention filter beds
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are commonly designed to be 18 to 36 inches deep. Therefore, an increase in the particle size
distribution of bioretention media (and infiltration rate) may not result in a significant reduction
in performance; instead, it may promote a greater utilization of the filter bed depth while
achieving similar overall performance.
For well-graded media beds (i.e., beds with a well-distributed range of particle sizes), the median
grain size is a poor proxy for the average pore size, and smaller particles may be retained through
cake and depth filtration mechanisms. Compared to sand filter media, bioretention media
typically contains a more heterogeneous mix of granular materials and organic materials, which
would limit the depth of particle penetration to a smaller depth than predicted by the classical
model based on median particle diameter.
The combination of these factors suggests that high flow rate bioretention media would not
necessarily achieve significantly lower particle removal than low flow rate media. This is
supported by Filterra® performance monitoring data as introduced and discussed later in this
paper.
3.2.2 Reactive Filtration
Beyond the mechanisms provided by inert filtration, reactive filtration involves three primary
mechanisms (Metcalf and Eddy 2003):
1. Chemical adsorption – bonding and chemical interaction
2. Physical adsorption – electrostatic forces, electrokinetic forces, and van der
Waals forces
3. Biological growth – growth of biological film; can be significant in continuously-
fed filters, but is uncommon in well-drained filters that are allowed to dry
between events
While inert filtration is the dominant removal mechanism for solids and particulate-bound
pollutants in bioretention systems, reactive filtration can play a major role in the removal of
dissolved constituents and very fine particles. In well drained systems (i.e., bioretention
systems), biological (biofilm) growth is limited. Therefore, reactive filtration generally includes
chemical and physical sorption processes—specifically precipitation, ion exchange, and
adsorption.
Precipitation primarily occurs when carbonates are released by the media and combined by
constituents in solution to form solid precipitates that are subsequently filtered by the media
matrix. Ion exchange involves the replacement of a charged media particle (e.g., Mn2+, Fe2+,
Ca2+) with a charged particle in solution (e.g., Cu2+, Zn2+). Adsorption primarily involves the
incorporation of constituents onto the surface of media particles by bonding, chemical
interactions, and to a lesser extent, molecular dipole attractions (i.e., van der Waals forces). The
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cation exchange capacity (CEC) of a reactive medium defines the bulk quantity of positively-
charged ions that can be exchanged or adsorbed. Materials such as granulated activated carbon
(GAC), zeolite, rhyolite, clays, diatomaceous earth, and organic matter all can have high CECs.
When analyzing pollutant affinity and reaction kinetics, two primary media characteristics are of
interest:
1. Equilibrium capacity – how much pollutant the media can retain
2. Reaction rate – how fast the media can retain the pollutant
Equilibrium capacity is defined by sorption isotherms that can be used to predict the amount of
pollutant removed at a known concentration for a fixed mass of media at a constant temperature
and pH. While various researchers have reported coefficients for their fitted isotherm models,
isotherms are not readily transferrable since they are specific to the media, solids gradation, and
water chemistry used in their development (WERF 2005). The reaction rates for the various
mechanisms also depend on the pollutant type, stormwater characteristics, water (e.g., pH,
temperature, etc.), and media characteristics. For example, phosphorus can generally be removed
in reactive filters through a combination of sorption and precipitation, depending on pH, with
reaction rates of minutes to several hours (WERF 2005).
Various materials used in media filters have a wide range of capacities and reaction rates to
accumulate and retain dissolved pollutants. Materials can be specifically selected and engineered
to have more reactive surfaces and a higher density of sorption sites. Based on extensive testing
of various media types, Johnson et al. (2003) found that a peat-sand mix, zeolite, compost, and
iron oxide-coated sand generally showed the best overall performance at removing dissolved
metals from stormwater. Literature suggests that contact times of several hours may be needed
for conventional materials found in bioretention media such as silica sand, loam soil, and
compost (e.g., Wanielista and Chang 2008; Sun and Davis 2007), but only a few minutes may be
needed for highly reactive media such as magnesium oxide-coated sand (e.g., Liu et al. 2004).
Johnson et al. (2003) found that increasing contact times beyond the scale of several minutes
does not to significantly improve treatment efficiency.
An optimized point can therefore be identified where the ability to treat a higher fraction of the
stormwater runoff volume is balanced with the ability to provide longer residence times. With
consideration of observed diminishing returns in treatment efficiency beyond the scale of several
minutes of residence time, the optimal design for space constrained locations likely lies in a
system with high media flow rate, specialized media, and relatively small footprint per unit
volume of water captured.
3.3 Inter-storm Treatment Processes
For well-drained bioretention systems, the inter-event volume stored equals the water content
associated with the field capacity of the porous media. The treatment processes that act upon this
inter-event volume include microbially-mediated transformations, biological uptake and storage,
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and volatilization. These processes are considered critical to retaining pollutants that have been
removed by within-storm processes and regenerating the capacity of reactive filtration processes.
Other important processes that occur between events include evaporation, surface drying/
cracking, plant activity (e.g., root growth/penetration, vegetative stabilization), and animal
activity (e.g., earthworm, insect, etc.), considered collectively as soil processes. These processes
are believed to be important to preserve the hydraulic function of bioretention media. Routine
maintenance is also considered to be an important inter-storm pollutant removal process.
3.3.1 Microbially-Mediated Transformations
Microbially-mediated transformations include the metabolic activity of bacteria, algae and fungi
that promotes degradation of organic pollutants and oxidation or reduction of inorganic
pollutants (WERF 2005). Metabolic activity is primarily associated with the natural biochemical
cycles of carbon, nitrogen, phosphorus, and sulfur (Crites and Tchabanoglous 1998). However,
xenobiotic metabolism (i.e., biotransformation of chemicals foreign to an organism) can play a
significant role in the transformation, stabilization, and detoxification of heavy metals and
organic chemicals.
Stormwater bioretention systems are variably-saturated and include root zone biomass that can
create pockets of aerobic and anaerobic conditions that promote diverse microbial activity. For
example, an aerobic environment is generally needed for nitrification (ammonia → nitrite →
nitrate) and an anaerobic environment is needed for denitrification (nitrate → nitrogen gas). If
this process is completed within a bioretention system, nitrogen can be removed. However,
anaerobic conditions are often not prevalent enough to cause large nitrate reductions. Clark and
Pitt (2009) evaluated the retention of pollutants for a variety of media types and found that
dissolved metals adsorbed to media are likely to be retained by most media types under both
aerobic and anaerobic conditions, but phosphorus release may occur during anaerobic conditions,
especially if the media contains highly organic compost.
Microorganisms within the root zone of plants can alter the pH and redox potential within the
soil, which can degrade organic chemicals, cause metals to precipitate, or convert various
pollutants into a form that can be accumulated or adsorbed by plants and microbes (McCutcheon
and Schnoor 2003). These microbially-mediated transformations have the ability to regenerate
the sorption capacity of filtration media between storms.
3.3.2 Biological Uptake and Sequestration
Biological uptake and sequestration as a pollutant removal mechanism refers to the removal of
organic and inorganic constituents from stormwater by plants and microorganisms through
nutrient uptake and bioaccumulation. Biological uptake results in the conversion of nutrients in
stormwater into living tissue, while bioaccumulation results in the sequestering of pollutants into
organisms regardless of what is immediately needed (WERF 2005). Organisms may assimilate
macronutrients such as phosphorus for metabolism and growth, in addition to micronutrients
Filterra® Bioretention Systems: Technical Basis for
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(i.e., some trace metals), and nonessential constituents (i.e., other trace metals). Phosphorus
uptake by plants and microbes may improve the capacity of the soil to adsorb other constituents.
Some plants sequester metals in the root zone, and expel matter that can foster metals
precipitation. Uptake of metals depends on bioavailability; some chemical forms are more
reactive and readily assimilated by biological matrices than others.
Uptake as a within-storm removal process may not be significant in high flow rate BMPs due to
the time needed for such processes; however, biological uptake is believed to help regenerate
media function between storms by freeing sorption sites and providing more permanent pollutant
retention mechanisms within biomass in the media.
3.3.3 Volatilization
Volatilization is the process of liquids and solids vaporizing and escaping to the atmosphere.
Compounds that readily evaporate at normal pressures and temperatures are considered volatile
compounds. While these compounds are not frequently detected in urban runoff, volatile organic
compounds (VOCs) or semi-volatile organic compounds (SVOCs) are sometimes present,
including various petroleum hydrocarbons (e.g., BTEX 1 and PAHs 2), gasoline oxygenates (e.g.,
MTBE 3), herbicides, and pesticides. VOCs can also be formed during some microbial and
phytochemical redox transformations of other pollutants in urban runoff. Volatile compounds are
usually highly soluble in water and can easily pass through bioretention systems if they are not
volatilized between storm events.
3.3.4 Bacterial Inactivation Processes
The term “inactivation” with respect to bacteria is analogous to sequestration of non-living
pollutants. Bacteria are removed from stormwater by the within-storm processes; particulate-
bound bacteria are predominantly addressed by physical filtration while free-floating bacteria are
predominantly addressed by reactive components of filtration (sorption). Once removed, other
processes may work to inactivate the bacteria so that they do not multiply or wash out in
subsequent events.
While limited study has been conducted, it is believed that inactivation processes of bacteria in
bioretention systems may include predation by other microorganisms (Ruby 2008), solar
irradiation of material retained on the surface of the media, and development of conditions
inhospitable for growth, including drying of media between storm events (Hunt and Lord 2010).
It is believed that the media goes through a maturation process where it develops a complex
microbiological ecosystem that enhances predation of bacteria (Ruby 2008). Studies have found
that long term removal efficiencies of over 90 percent can be achieved by bioretention systems
(Ruby 2008; Hunt and Lord 2006), indicating that slow media flow rates do not necessarily result
in higher initial removal and inactivation (Ruby 2008).
1 Benzene, toluene, ethylbenzene, and xylenes
2 Polycyclic aromatic hydrocarbon
3 Methyl tert-butyl ether
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3.3.5 Soil Processes
Soil processes means evapotranspiration, surface weathering, plant activity (e.g., root growth and
penetration, vegetative stabilization), animal activity (e.g., earthworms, insects), and other
processes (e.g., fungal activity).
Evapotranspiration is the combined effects of evaporation and
transpiration in reducing the volume of water in a vegetated area during a
specific period of time. The volume of water in the root zone of soils is
taken up by roots and then transpired through the leaves of the plant. The
suction pressure exerted by evapotranspiration may have the effect of
loosening soil that may have been compacted by hydraulic impact (i.e., the
downward forces of incoming stormwater) during an event. Drying of the
media can exert environmental stress on pathogenic bacteria that are
retained in the media via desiccation, contributing to inactivation of these
constituents (Crites and Tchobanoglous 1998).
Weathering (i.e., drying or cracking) is caused by evaporation, media
expansion and contraction, and other physical processes and that can break
up accumulated surface sediment and cause internal adjustments to the
structure of the media matrix. Unlike mineral sands; peats, zeolites, and
loams have high internal porosity and therefore, can exhibit more dramatic
expansion and contraction during hydration and dehydration processes.
Li and Davis (2008) state that compared to rigid sand filter media,
bioretention media is relatively plastic, allowing for media shape
adjustments to incorporate captured particles and improve the infiltration
capacity during the dry period.
Plant activity in the media layer can be important for preserving and
regenerating hydraulic function, stabilizing accumulated sediment, and
preserving/increasing levels of organic matter in the soil. In addition, the
movement of plant stalks due to wind and bird activity can break up
surface crusts thereby maintaining or increasing infiltration rates. Plant
roots contract and expand depending on water availability which helps to
develop preferential flow pathways. Plant roots also increase aeration and
void space by breaking up the media for water and oxygen to permeate.
Root growth aids in the development of healthy and biologically-active
soil structures and can increase infiltration rates over time due to the
creation of macropores in the media (Facility for Advancing Water
Biofiltration in Australia 2008; PGC-DER 2009).
Animal activity in the soil layer can be important for maintaining or
increasing porosity, preserving hydraulic function over the long term,
preserving or increasing the organic content of the soil, and stimulating
microbial activity (Nogaro et al. 2006; Nogaro et al. 2007; Derouard
1997). Worms aid in the development of natural soil structure over time,
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which can increase infiltration rates. Worms create cavities and worm
castings can help with soil aggregation as well as pollutant removal.
Other processes, such as those performed by fungi, also may play a
critical role in maintaining aggregate stability within the media. For
example, fungi contain individual fungal filaments known as hyphae,
which together form mycelia and aid in soil structure stabilization. Fungi
also excrete microbial slime that aids in aggregation. In addition,
mycorrhizae fungi located on and within the plant root system aid in water
and pollutant uptake.
3.3.6 Routine Maintenance as a Pollutant Removal Mechanism
Particulate “break-through” in bioretention systems may occur if fine particles migrate through
the media bed. In addition, reductions in hydraulic capacity may result from an increase in the
percentage of fine particles in the media bed, resulting in greater frequency of bypass of the
system. Finally, dissolved constituent break-through is possible due to short-circuiting or
depletion of adsorption sites. Maintenance activities, in addition to inter-storm processes, can
promote effective long-term inert and reactive filtration. The removal of accumulated sediment
at the surface of the system and removal and replacement of the surface mulch layer may have
the following effects:
Reduces the potential for migration of particles from the surface cake
layer into the media bed
Permanently removes the dissolved constituents adsorbed to accumulated
sediment and mulch
Refreshes the adsorption capacity of the entire bed through the addition of
new mulch
The accumulation of fines in the filter media theoretically improves the ability of the media to
remove pollutants; however, these fines also tend to decrease the media filtration rate over time
which can reduce the capture efficiency of the BMP. The effect of reduction in media flow rate
on the capture efficiency achieved by a Filterra® system is shown for an example location in
Figure 1. As this figure illustrates, the influence of reduction in media flow rate on capture
efficiency is relatively minor; a reduction in media flow rate of 50 percent from 140 to 70
inches/hour results in an expected decline in capture efficiency of less than 10 percent. This is
explained by the fact that smaller, more frequent storms contribute the majority of average
annual runoff volume. Relationships will vary based on precipitation patterns of an area, but the
general nonlinear trend is expected to be consistent across a wide range of climates.
3.4 Summary of Unit Treatment Processes
Table 2 summarizes unit treatment processes provided by bioretention systems and the pollutant
or conditions that they are intended to address or support.
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Figure 1. Effect of media flow rate on capture efficiency in Fairfax County, Virginia
(adapted from Geosyntec 2008a, 6’× 6’ Filterra®, 0.23-acre tributary area).
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Table 2. Summary of unit treatment processes and pollutant removal.
Unit Removal Processes
Potentially Provided by
Bioretention Systems
Pollutant Removal
Other Performance
Factors Particulates and Particulate-bound Dissolved Metals Dissolved Nitrogen Dissolved Phosphorus Bacteria Oil and Grease VOCs and SVOCs Hydraulic Capture Efficiency Volume Reduction Inert Filtration NA NA
Reactive Filtration NA NA
Microbially-mediated
Transformations NA NA
Biological Uptake and Storage NA NA
Volatilization NA NA
Bacterial Inactivation
Processes NA NA
Soil Processes
Routine Maintenance NA
Primary removal mechanism in bioretention systems
Generally limited removal mechanism in bioretention systems unless specific design attributes are included
Supporting process in well-drained bioretention systems
Process with no contribution or unknown contribution to pollutant removal
NA: not applicable; VOCs: volatile organic compounds; SVOCs: semi-volatile organic compounds
S S S S S S S
S S S S S S S S S
S S
M S
S S S S S
S S S S S
M M
M
S
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4. Filterra® Bioretention Stormwater Treatment System
4.1 System Components and Unit Treatment Processes
The Filterra® system is housed in a precast concrete curb inlet structure with a tree frame and
grate cast in the top slab, and includes engineered filter media topped with mulch that supports a
tree or other type of plant (Figure 2). The following sections describe the three key pollutant
removal components of the Filterra® system: mulch, engineered filter media, and vegetation and
other system biota.
Figure 2. Typical Filterra® system design.
4.1.1 Mulch
The Filterra® system includes a 3-inch layer of shredded wooden mulch. The mulch provides
pretreatment and protection of the engineered filter media, and is expected to perform the
following within-storm unit treatment processes:
Inert filtration
Reactive filtration
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To promote filtration, the Filterra® system is typically designed with approximately 6 inches of
freeboard above the top of the mulch to the gutter elevation at the curb face. This ponding area
provides surface storage for a portion of the water quality treatment volume and promotes
settling of fine particles present in the stormwater on the surface of the mulch (CWP 1996). The
mulch layer filters out large particles (gross and suspended solids) present in the stormwater that
might otherwise prematurely clog the media. Because the mulch is heterogeneous, it captures
relatively small particles without limiting the hydraulics of the system. The amount of inert
filtration that occurs in the mulch layer is a function of particle density, size, and water density.
Mulch also supports reactive filtration processes. Due to the high CEC present in organic matter
contained in the mulch layer, the mulch adsorbs dissolved pollutants, such as heavy metals.
Mulch also provides a constant supply of organic material to the media from mulch fines to
sustain the CEC of the media for removal of dissolved constituents.
The mulch layer also helps to retain moisture in the Filterra® system, which supports vegetation
growth, decomposition of organic matter, and microbial communities (CWP 1996). This
moisture retention may lead to a lower frequency of irrigation requirements for system
maintenance. Semi-annual removal and replacement of the mulch layer allows for removal of
pollutants that have been absorbed by the mulch, as well as trash, debris, and silt that have
accumulated on top of the mulch layer.
4.1.2 Media
The mulch layer is underlain by 1.5 to 3.5 feet of engineered filter media, consisting of a
specified gradation of washed aggregate and organic material homogeneously blended under
strict quality controlled conditions. The engineered filter media is tested for hydraulic
functionality, fertility, and particle size distribution to ensure uniform performance. At a design
infiltration rate of 100 to 140 inches/hour, a media bed depth of 2.0 feet, and a porosity of
40 percent, the steady state residence time in the media layer would be approximately 4 to 6
minutes. While initial flows entering a dry system may begin to discharge somewhat more
quickly than steady state as a result of initial wetting processes, the calculated steady state
residence time (4 to 6 minutes) is expected to be provided for the great majority of volume
during each storm event and is therefore considered to be characteristic of Filterra® system
operation. The media is expected to perform the following within-storm unit treatment processes:
Inert filtration
Reactive filtration
Using data from studies conducted by the University of Virginia (2001), the filter media was
optimized to operate under high flow rates while maintaining pollutant removal performance.
The engineered filter media contains hydrophilic adsorbents such as aluminosilicates (sand) and
hydrophobic adsorbents such as carbonaceous/organic matter, which have been included to
promote the partitioning of pollutants to the soil particles. The combination of hydrophilic and
hydrophobic adsorbents is designed to capture a wide range of pollutants through physical
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adsorption (e.g., electrostatic forces). The amount of adsorption that occurs is a function of the
available surface area and the polarity of the constituents passing through the Filterra® system.
As discussed in the previous section, media specifically designed for rapid reactive filtration can
achieve significant removal on the order of several minutes (consistent with the 4- to 6-minute
characteristic residences time calculated for the Filterra® system).
The media is also expected to perform the following inter-storm unit treatment processes:
Microbially-mediated transformations
Biological uptake and storage
Volatilization
The engineered filter media is designed with a high percentage of organic material for uptake of
nutrients and other pollutants. Organic material is added for initial organic complexing (i.e.,
cation exchange) with pollutants and to help promote biological growth. The mulch, rhizosphere
degradation, and runoff continuously add organics to the media to replace the amount lost to
microbiological processes.
Bacterial growth, supported by the root system and organic soil content, also contributes to
pollutant removal and are a function of moisture, temperature, pH, salinity, pollutant
concentrations (particularly toxins), and available oxygen. In addition, volatilization may also
occur if VOCs (i.e., gasoline) are captured in the filter media.
Finally, the wetting and drying of the media during and after storm events expand and contract
organics in the system, which help in the creation of preferential flow pathways (Americast, Inc.
2009a).
4.1.3 Vegetation and Other System Biota
The Filterra® system includes a vegetation component selected based on aesthetics, local climatic
conditions, traffic safety (i.e., limiting the height or breadth of the vegetation), and maintenance
considerations (i.e., may restrict deciduous vegetation).
The selected vegetation may include flowers, grasses, a shrub, or a tree, and is expected to
perform the following inter-storm unit treatment processes:
Microbially-mediated transformations
Biological uptake and storage
Soil processes
As discussed previously, microorganisms present in the root zone of the vegetation in the
Filterra® system can assist with adsorption of pollutants into the media layer and regeneration of
the sorption capacity of the media between storm events. Bacterial growth on the root system can
bind with particulate organic matter and heavy metals. Growth of vegetation in the Filterra®
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system also requires macronutrients (i.e., nitrogen and phosphorus) and micronutrients (i.e.,
metals) found in stormwater runoff for metabolic processes (i.e., energy production and growth).
As the biomass (i.e., plant and microbes) of the Filterra® system grows, it is assumed that the
system’s capacity to capture and process more pollutants increases (Ruby and Appleton 2010).
This increase in biomass not only increases infiltration rates but also the surface area of the roots,
allowing for increased pollutant adsorption and creation of additional pore space in the media
layer. Filterra® systems have also been observed to contain fungi and worms which help with
media stabilization, aggregation, and development of the media structure over time, maintaining
the flow rate capacity of the system.
4.2 Results Documenting High Flow Rate Treatment from Bench-scale Testing
Third-party bench-scale testing efforts have been conducted to evaluate achievable treatment
flow rates and particle removal performance of the media in the Filterra® system. Summaries of
these independent studies are provided below.
4.2.1 Media Flow Rates in Bench-scale Testing
Column tests were completed by GeoTesting Express (2005) to support Technology Assessment
Protocol-Ecology (TAPE) monitoring in Washington State. The specific goal of these column
tests was to evaluate flow rates in heavily- and lightly-compacted media. Measured infiltration
rates were approximately 50 inches/hour for heavily-compacted media, and 300 inches/hour for
lightly-compacted media. Under normal operating conditions and maintenance schedules, the
Filterra® system media is expected to perform between these extremes. The concrete top slab
covering the Filterra® system is also designed to protect the media from vehicular and foot traffic
which would prevent heavy compaction of the media from occurring and would maintain the
high flow rate capacity of the system.
4.2.2 Bench-scale Testing of TSS Removal
Two bench-scale analyses were conducted to evaluate removal of TSS by Filterra® system
media.
Geosyntec Consultants (2006) conducted a column study to analyze the TSS treatment
performance of the Filterra® system media. A manufactured silica product (Sil-Co-Sil 106)
with a size distribution consisting of 80 percent of the particle mass less than 50 microns (µm)
was selected to simulate expected influent TSS from an urban setting. A total of 15 treatment
simulations were conducted, with influent TSS concentrations ranging from 8.3 to
260 milligrams per liter (mg/L) and hydraulic loading rates of 50 to 55 inches/hour. The effluent
TSS concentrations were consistently less than 20 mg/L for all simulations and the median
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effluent TSS concentration was 7.8 mg/L. The TSS removal ranged from 70 to 95 percent with a
median removal of 90.7 percent 4.
Americast, Inc. conducted a second column study in 2009 to investigate how hydraulic loading
affects the TSS treatment performance of the Filterra® system media. Sil-Co-Sil 106 was used to
represent the particle size distribution typical of TSS in urban runoff. Thirty events were
simulated with flow rates ranging from 25 to 150 inches/hour and influent TSS concentrations
ranging from 42 to 252 mg/L. The effluent TSS concentration ranged from 0.8 to 42.8 with a
median of 5.1 mg/L. The TSS removal ranged from 25 to 99.5 percent with a median removal of
96.7 percent. Mehta and Williamson (2009) conducted a third-party review of this study. No
statistically significant correlation was found between hydraulic loading and effluent
concentration (Mehta and Williamson 2009). Similarly, no significant correlations between
influent and effluent TSS concentrations were found. Figure 3 compares the effluent TSS
concentrations to flow rates and influent TSS concentrations. Note the very low coefficient of
determination (R2) and the statistically insignificant p-value (>0.05) for both regression lines.
-20
-10
0
10
20
30
40
50
20 40 60 80 100 120 140 160Effluent (mg/L)Flowrate (in/hr)
Linear fit (9.257 -0.02234x)
95% CI
R2 = 0.01
p-value = 0.58
-20
-10
0
10
20
30
40
50
0 50 100 150 200 250 300Effluent (mg/L)Influent (mg/L)
Linear fit (9.613 -0.01641x)
95% CI
R2 = 0.02
p-value = 0.50
Figure 3. Effluent TSS concentration compared to flow rate and influent TSS concentration.
4 In general, the concept of a percent reduction should be applied with caution as a sole means of quantifying
stormwater treatment performance, particularly because this estimator is inherently biased towards “dirtier” sites,
(i.e., those with relatively high influent levels) (Strecker et al. [2001]). When influent levels are low, it becomes
increasingly difficult to achieve a dramatic percent reduction; furthermore, variability inherent to the analysis
methods, sampling procedures and other factors unrelated to actual treatment performance have an exaggerated
influence on the result when influent is very close to effluent. Where used, percent reductions should be reported
with observed influent and effluent concentrations.
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4.2.3 Applicability of Bench-scale Testing to Field Performance
The controlled lab experiments indicate that media flow rates greater than 100 inches/hour
and significant removal of small particles are possible using Filterra® system media. Both
studies described previously were performed using a rigorous testing protocol designed to
mimic typical stormwater characteristics and media placement in the field. Compared to field
studies, laboratory studies allow for control of environmental conditions, flow rates, influent
concentrations, and particle size distributions. Controlled experiments reduce the number of
variables that may influence performance, providing higher confidence in the collected data and
eliminating the site specificity of the study. For these reasons, the results of the laboratory
studies can be more generally applicable than field study results at a particular location.
Because stormwater characteristics vary significantly from site to site, the results of laboratory
studies are not a reliable predictor of performance for a specific site during a specific storm
event. However, these studies can inform estimates of average performance under average
stormwater conditions, and provide cross-validation of results obtained during field-scale testing.
4.3 Results Documenting High Flow Rate Treatment from Full-scale Testing
4.3.1 Evaluation of Hydrologic Performance
Maximum capacity flow rate tests performed on 10 different Filterra® systems of varying age
(recently activated to 3 years) and varying maintenance periods (recently maintained to 2 years
without maintenance) demonstrated that the saturated hydraulic conductivity (Ksat) of Filterra®
media ranged from 86 inches per hour to 205 inches per hour, with a 95th percent confidence
interval on the median of 129 to 197 inches per hour. Tests included two systems with greater
than or equal to 4.5 inches of sediment accumulation. While the results from the sediment-laden
systems were not found to be true statistical outliers, the range of observed Ksat without these
studies was 152 to 205 inches per hour. From these tests, a design media flow rate of 140 inches
per hour was recommended, based on the lower 95th percent confidence limit of all data points
(including sediment-laden system), adjusted to account for driving head on the system under
normal operation (Geosyntec 2008b). Different wetting periods were also tested during these
flow rate studies, looking at both constant and periodic wetting. These studies showed that
Filterra® systems that received a periodic introduction of runoff (i.e., similar to that of a typical
storm event) achieved the highest flow rate. In general, the media is well drained under normal
operating conditions.
Core samples collected from 11 Filterra® systems of different ages (6 to 18 months) with no
maintenance showed that there was not a significant change in the particle size distribution of the
media and the amount of silts and clays up to 18 months after installation (Brim 2007). Four core
samples were collected from each Filterra® system and the particle size distribution in the top
10 centimeters of the media was evaluated. All of the evaluated systems contained a percentage
of fine particles that matched the Filterra® system media specification, demonstrating that
significant media degradation had not occurred. (However, the younger systems had relatively
higher accumulations of fine particles than the older systems due to a difference in drainage area
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size and stormwater runoff quality.) These findings reinforce the important role that the mulch
plays in capturing relatively small particles without limiting the hydraulic capacity of the system.
4.3.2 Evaluation of Water Quality Treatment Performance
This section presents water quality treatment performance data collected from the following
Filterra® installations:
One Filterra® system installation in Falls Church, Virginia (Technology
Acceptance Reciprocity Partnership [TARP] study and TARP addendum)
Three Filterra® system installations in Maryland and Virginia
(performance over time study)
Two Filterra® system installations at the Port of Tacoma in Tacoma,
Washington (TAPE study)
One Filterra® system installation in Bellingham, Washington (Bellingham
study)
The TARP study was conducted from October 2004 through November 2005 to obtain approval
for basic treatment in California, Massachusetts, Maryland, New Jersey, Pennsylvania, and
Virginia (Yu and Stanford 2006). The TARP addendum study using simulated storm events was
conducted in December 2006 and January 2007 to supplement the TSS and total phosphorus data
presented in the TARP (ATR Associates 2009). The performance over time study was conducted
from January 2008 through February 2010 on three Filterra® systems installed in restaurant, oil
service station, and gas station parking lots (Americast, Inc. 2009b). The Filterra® systems
monitored for the performance over time study ranged in age from 2 years (restaurant parking
lot) to 5 years (gas station parking lot). The TAPE study was conducted from May 2008 through
May 2009 at two sites at the Port of Tacoma (POT1 and POT2 test systems) to obtain a General
Use Level Designation (GULD) basic, enhanced (dissolved metals), and oil treatment from the
Washington Department of Ecology (Ecology) (Herrera 2009). The Bellingham study was
conducted from March 2009 through April 2010 to test the phosphorus removal performance of
the Filterra® system (M. Ruby, personal communication, June 8, 2010).
The pollutant removal performance of these systems was evaluated based on flow-weighted
composite samples and discrete grab samples that were collected from influent and effluent of
each system during storm events. Automated samplers were used to collect flow-weighted
composite samples of the influent and effluent during discrete storm events for the TARP,
TAPE, and Bellingham studies. Flow-weighted composite samples were manually collected
during the TARP addendum study. Discrete grab samples were also collected for the TAPE
study for TPH analysis. All samples collected for the performance over time study were discrete
grab samples.
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The pollutant removal performance was quantified based on efficiency ratios that were
calculated for each parameter using the following equation:
where:
EF = efficiency ratio
Ceffluent = mean or median effluent concentration
Cinfluent = mean or median influent concentration
The efficiency ratio is a commonly used method for calculating pollutant removal performance
(Geosyntec et al. 2002; CWP 2008). It was calculated based on event mean concentrations
(EMC) from the flow-weighted composite samples that were collected for the TARP and TAPE
studies, and concentrations from discrete samples that were collected for the performance over
time study. In each case, the efficiency ratios were computed based on the mean influent and
effluent concentrations if the associated data were found to potentially arise from a normal
distribution (i.e., the null hypothesis that the data come from a normal distribution could not be
rejected at an alpha significance level of 0.05 using a Shapiro-Wilk test). If the data had a non-
normal distribution, a natural logarithmic transformation was applied to the influent and effluent
concentrations. The transformed data were then analyzed to determine if they have a normal
distribution. If this proved to be the case, the mean and standard deviation of the log transformed
data were used to calculate arithmetic estimates of the means in their original units and used to
calculate the efficiency ratios. If the log transformed data of either the influent or effluent did not
have a normal distribution, the efficiency ratios were calculated based on the median influent and
effluent concentrations.
Results from all five studies were fairly consistent for TSS with efficiency ratios ranging from
83.3 percent (ATR Associates 2009) to 88.3 percent (Americast, Inc. 2009b) (Table 3). The
efficiency ratio for total phosphorus had a much wider range from 8.5 percent (Herrera 2009) to
69.5 percent (ATR Associates 2009) due to low total phosphorus concentrations and high soluble
reactive phosphorus fractions measured during the TAPE study. Follow-up field testing in two
more typical urban applications for phosphorus monitoring under TAPE is pending. TKN was
only measured during the TARP study and had a removal efficiency of 39.5 percent (Yu and
Stanford 2006). The efficiency ratio for total copper ranged from 33.2 percent (Yu and Stanford
2006) to 76.9 percent (Americast, Inc. 2009b), while dissolved copper was only monitored
during the TAPE study and had an efficiency ratio of 48.0 percent. The efficiency ratio for total
zinc removal ranged from 48.1 percent (Yu and Stanford 2006) to 78.7 percent (Americast, Inc.
2009b), while dissolved zinc had an efficiency ratio of 54.9 percent during the TAPE study. The
oil and grease efficiency ratio measured during the performance over time study was lower than
expected (58.6 percent) due to low influent concentrations near the detection limit; however, the
TPH efficiency ratio calculated for the TAPE study was 96.1 percent (Herrera 2009).
Infleunt
Effuent
C
CEF−=1
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Table 3. Pollutant removal performance of the Filterra® system.
Pollutant n
Median
Influent
(mg/L) a
Median
Effluent
(mg/L) a
Mean
Influent
(mg/L) a
Mean
Effluent
(mg/L) a
Effluent <
Influent?
Efficiency
Ratio Reference
Total Suspended
Solids
11 20 2.5 U 28.8 5.2 Yes b 87.5% d TARP
7 63.4 11.6 66.3 11.1 Yes c 83.3% e TARP Addendum
34 38.0 4.1 71.0 f 8.3 f Yes c 88.3% f Perf. Over Time
18 36.3 4.8 68.9 7.4 Yes b 86.9% d Bellingham g
10 27.5 4.2 28.8 4.3 Yes c 85.2% e TAPE g
Total Phosphorus 14 0.14 0.076 0.23 0.090 Yes c 59.7% f TARP
6 0.52 0.16 0.59 0.18 Yes c 69.5% f TARP Addendum
41 0.29 0.16 1.15 0.49 Yes b 44.8% d Perf. Over Time
15 0.12 0.054 0.16 0.065 Yes b 56.5% d Bellingham h
12 0.15 0.14 0.19 f 0.17 f No c 8.5% f TAPE h,i
Total Kjeldahl
Nitrogen
6 1.90 1.15 2.22 1.27 Yes b 39.5% d TARP
Total Copper 8 0.012 0.01 U 0.015 0.01 U No c 33.2% f TARP
30 0.061 0.014 0.083 0.029 Yes b 76.9% d Perf. Over Time
29 0.0081 0.0034 0.0082 0.0037 Yes b 58.0% d TAPE
Dissolved Copper 23 0.0056 0.0033 0.0070 f 0.0036 f Yes c 48.0% f TAPE j
Total Zinc 16 0.039 0.02 U 0.070 0.023 Yes b 48.1% d TARP
30 0.355 0.08 88.7 18.1 Yes b 78.7% d Perf. Over Time
29 0.384 0.102 0.516 0.230 Yes b 73.4% d TAPE
Dissolved Zinc 23 0.194 0.082 0.267 f 0.120 f Yes c 54.9% f TAPE k
Oil & Grease 20 7.0 2.9 26.8 4.2 Yes b 58.6% d Perf. Over Time l
TPH 12 43.4 1.2 55.7 f 2.2 f Yes c 96.1% f TAPE m
mg/L: milligrams per liter
U: at or below detection limit
TARP: Technology Acceptance Reciprocity Partnership study conducted in Falls Church, Virginia (Yu and Stanford 2006)
TARP Addendum: Technical Report Addendum Additional Field Testing and Statistical Analysis conducted in Falls Church,
Virginia (ATR Associates 2009)
Perf. Over Time: Performance Over Time study conducted in Maryland and Virginia (Americast 2009b)
Bellingham: study conducted in Bellingham, Washington, not all data summarized meets storm coverage criteria and post-storm
dry period data required by TAPE (M. Ruby, personal communication, June 8, 2010)
TAPE: Technology Assessment Protocol – Ecology study conducted in Tacoma, Washington (Herrera 2009)
a Non-detect values (U) assigned a value of one-half the detection limit in calculations.
b Based on a Wilcoxon signed-rank test (1-tailed) test with a significance level at p<0.05.
c Based on a paired t-test with a significance level at p<0.05.
d Based on median influent and effluent concentrations.
e Based on mean influent and effluent concentrations.
f Based on arithmetic estimate of the mean computed from log-transformed influent and effluent concentrations.
g TSS data in the influent range accepted by Ecology (20 mg/L and greater).
h TP data in the influent range accepted by Ecology (0.1 to 0.5 mg/L).
i Low TP removal due to anomalous phosphorus data collected at the Port of Tacoma included very low TP influent
concentrations and a high fraction of soluble reactive phosphorus.
j Dissolved copper data in the influent range accepted by Ecology (0.0029 to 0.02 mg/L).
k Dissolved zinc data in the influent range accepted by Ecology (0.02 to 0.6 mg/L).
l Low oil and grease removal due to low influent concentrations near the detection limit (5.0 mg/L).
m TPH data in the influent range accepted by Ecology (10 mg/L and greater).
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Table 4 compares effluent concentrations for the Filterra® system from the five studies identified
above to typical effluent concentrations for biofilters and media filters; two categories of BMPs
reported in the International Stormwater BMP Database that generally provide similar unit
treatment processes to Filterra® systems. Performance summaries for the biofilter and media
filter classes of BMPs were derived from studies of the International Stormwater BMP Database
(Geosyntec and WWE 2008a, 2008b). For reference, Table 4 also presents influent
concentrations that were measured during the sampling of each system. These data generally
show that effluent concentrations for the Filterra® system are equivalent or slightly lower than
those from the other two BMP types. All the systems were able to achieve significant reductions
in influent concentrations for the following parameters: TSS, total zinc, dissolved zinc and total
copper, and dissolved copper. Biofilters and Filterra® systems were also able to achieve
significant reductions in influent dissolved zinc concentrations. Finally, media filters and
Filterra® systems were able achieve significant reductions in influent total phosphorus
concentrations.
4.3.3 Evaluation of Hydraulic Loading Rate
To evaluate Filterra® system performance as a function of hydraulic loading, the following three
types of hydraulic loading rates were calculated from data collected during the TAPE study:
1. Average hydraulic loading rate: average flow rate across entire sampled
storm event
2. Peak hydraulic loading rate: maximum flow rate across entire sampled
storm event
3. Average instantaneous hydraulic loading rate: average of flow rates
measured during collection of individual aliquots for flow-weighted
composite samples
All three types of hydraulic loading rates were calculated for each of the 22 sampled storm
events sampled for TSS during the TAPE study (POT1 test system). Based on these calculations,
the average hydraulic loading rate from storm events sampled for TSS ranged from 5 to
36 inches/hour, the peak hydraulic loading rates ranged from 14 to 133 inches/hour, and the
average instantaneous hydraulic loading rates ranged from 8.6 to 53 inches per hour. Because
composite samples are flow-weighted, the samples tend to be weighted towards system
performance under higher hydraulic loading; therefore, the majority of the runoff volume in the
sampled storms occurred during periods of high flow.
The average and peak hydraulic loading rates were also calculated for each of the 23 sampled
storm events sampled for dissolved metals during the TAPE study (POT1 and POT2 test
systems). Based on these calculations, the average hydraulic loading rate from storm events
sampled for dissolved metals ranged from 5 to 55 inches/hour, the peak hydraulic loading rates
ranged from 14 to 133 inches/hour, and the average instantaneous hydraulic loading rate ranged
from 8.6 to 81 inches per hour.
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Table 4. Typical influent and effluent concentrations in the International Stormwater Best Management Practice Database
and for the Filterra® system.
Pollutant Units
Biofilter Media Filter Filterra® System
Influent
Range
Effluent
Range
Effluent
< Influent? a
Influent
Range
Effluent
Range
Effluent
< Influent? a
Influent
Range
Effluent
Range
Effluent
< Influent? b
Total Suspended Solids mg/L 41-63 15-33 Yes 27-60 9.7-22 Yes 31-41 3.5-5.0 Yes
Total Phosphorus mg/L 0.22-0.28 0.26-0.41 No 0.15-0.26 0.11-0.16 Yes 0.16-0.25 0.08-0.14 Yes
Total Copper µg/L 25-39 7.7-14 Yes 11-18 8.2-12 Yes 9.3-26 4.3-10 Yes
Dissolved Copper µg/L 10-18 5.7-12 Yes 4.6-11 7.3-11 No 4.5-7.0 2.6-3.9 Yes
Total Zinc µg/L 128-225 28-52 Yes 52-132 17-59 Yes 158-290 41-80 Yes
Dissolved Zinc µg/L 33-79 19-32 Yes 38-101 29-74 Yes 177-322 75-110 Yes
mg/L: milligrams per liter
µg/L: micrograms per liter
Influent and effluent ranges are calculated based on the 95 percent confidence intervals about the median for the ISBMPD (Geosyntec and WWE 2008a) and five Filterra® field
studies (Yu and Stanford 2006; ATR Associates 2009; Americast, Inc. 2009b; Herrera 2009; M. Ruby personal communication, June 8, 2010).
a Based on a non-parametric analysis of the difference in median values of site averages (Geosyntec and WWE 2008b).
b Based on a Wilcoxon signed-rank (1-tailed) test with a significance level at p<0.05.
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To evaluate potential influences on system performance, correlation analyses were performed on
the TSS, dissolved copper, and dissolved zinc data from the TAPE study to determine if effluent
concentrations varied in relation to any of the following variables: influent concentration,
average hydraulic loading, average instantaneous hydraulic loading, and peak hydraulic loading.
Computed correlation coefficients (Spearman’s rho) from these analyses are presented in Table 5
while graphical representations of these relationships are shown in Figure 4 using matrix
scatter plots. These results indicate that effluent concentrations for all three parameters show
a significant positive correlation with influent concentrations; in other words, effluent
concentrations decreased when influent concentrations decreased. When the various measures of
hydraulic loading are examined, the results indicate that dissolved copper shows a negative
correlation with both average instantaneous hydraulic loading, and peak hydraulic loading. In
addition, dissolved zinc shows a negative correlation with peak hydraulic loading.
Table 5. Correlation between influent concentration, effluent concentration, and
hydraulic loading at the Port of Tacoma in Tacoma, Washington.
Pollutant Correlation Parameter
Influent
Concentration
Average
Hydraulic
Loading
Average
Instantaneous
Hydraulic Loading
Peak
Hydraulic
Loading
Total
Suspended
Solids
Spearman's rho 0.49 -0.15 0.11 0.15
95% Confidence Interval 0.09 to 0.76 -0.54 to 0.29 -0.33 to 0.51 -0.29 to 0.54
p-value 0.020 0.493 0.636 0.514
Dissolved
Copper
Spearman's rho 0.91 -0.32 -0.43 -0.45
95% Confidence Interval 0.8 to 0.96 -0.65 to 0.1 -0.71 to -0.02 -0.73 to -0.04
p-value 0.000 0.134 0.042 0.032
Dissolved
Zinc
Spearman's rho 0.51 -0.23 -0.28 -0.50
95% Confidence Interval 0.06 to 0.79 -0.63 to 0.26 -0.66 to 0.21 -0.78 to -0.04
p-value 0.030 0.351 0.253 0.034
Bolded values are significant at p <0.05 at the 95% confidence level.
While these results would seem to indicate that effluent concentrations are decreasing as
hydraulic loading increases, it is more likely that other confounding factors are influencing these
relationships. Specifically, influent concentrations of both dissolved copper and zinc may be
decreasing as hydraulic loading increases due to dilution. Therefore, the primary influence in
these relationships is likely influent concentration and not hydraulic loading; as noted above, the
correlations analyses show that effluent concentrations for these parameters decrease when
influent concentrations decrease.
Correlations analyses were also performed to determine if percent removal for the parameters
identified above varied in relations to average hydraulic loading, average instantaneous hydraulic
loading, and peak hydraulic loading. Computed correlation coefficients from these analyses are
presented in Table 6 while graphical representations of these relationships are shown in Figure 5
using matrix scatter plots. These results show there was generally no correlation between the
various measures of hydraulic loading and percent removal with one exception: percent removal
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for dissolved copper was negatively correlated with average hydraulic loading rate. Again, the
primary influence in this relationship is likely influent concentration and not hydraulic loading.
Specifically, as average hydraulic loading rate increases, influent concentrations decrease and
become more difficult to treat.
Figure 4. Matrix scatter plots showing relationships between effluent concentration and
the following variables: influent concentration, average hydraulic loading,
average instantaneous hydraulic loading, and peak hydraulic loading.
9 18 27 36 45Inf. TSS (mg/L)
1
2
3
4
5
6
7
8
Eff. TSS (mg/L)0 10 20 30 40Ave. Flow (in/hr)0 15 30 45 60Inst. Flow (in/hr)04080120160Peak Flow (in/hr)
0 5 10 15 20Inf. DCu (ug/L)
12345678910Eff. DCu (ug/L)0 10 20 30 40Ave. Flow (in/hr)0 15 30 45 60Inst. Flow (in/hr)04080120160Peak Flow (in/hr)90180270360450Inf. DZn (ug/L)
0
50
100
150
200
250
Eff. DZn (ug/L)0 10 20 30 40Ave. Flow (in/hr)0 15 30 45 60Inst. Flow (in/hr)04080120160Peak Flow (in/hr)
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Table 6. Correlation between percent removal and hydraulic loading at the Port of
Tacoma in Tacoma, Washington.
Pollutant Correlation Parameter
Average Hydraulic
Loading
Average Instantaneous
Hydraulic Loading
Peak Hydraulic
Loading
Total Suspended
Solids
Spearman's rho -0.17 -0.05 -0.10
95% Confidence Interval -0.55 to 0.27 -0.46 to 0.38 -0.5 to 0.33
p-value 0.450 0.832 0.645
Dissolved Copper Spearman's rho -0.47 -0.29 -0.36
95% Confidence Interval -0.74 to -0.08 -0.63 to 0.13 -0.67 to 0.06
p-value 0.022 0.173 0.090
Dissolved Zinc Spearman's rho -0.04 0.13 0.34
95% Confidence Interval -0.49 to 0.44 -0.36 to 0.56 -0.15 to 0.7
p-value 0.887 0.616 0.168
Bolded values are significant at p <0.05 at the 95% confidence level.
in/hr: inches per hour
mg/L: milligrams per liter
4.4 Maintenance
The major challenge to the longevity of the Filterra® system is sediment buildup on the surface
of the Filterra® system, which could restrict free flow of runoff, trash and debris into the system.
As long as routine maintenance is performed, the Filterra® system will theoretically last
indefinitely, since it essentially sequesters and recycles nutrients, metals, and organics in the
biomass (i.e., plant and microbes). The only major maintenance required would be replacement
of the plant if it should die. As long as the plant is thriving, the Filterra® system should function
as designed.
Contech Engineered Solutions recommends a semiannual maintenance schedule for installations
on the east coast and an annual maintenance schedule for installations on the west coast.
However, in industrial areas with heavy petroleum loading, the frequency of maintenance may
need to be increased to maintain the flow rate of the mulch layer that protects the filtration
media. For other land use applications where petroleum loadings are expected to be lower,
progressive accumulation of petroleum that leads to reduction in hydraulic capacity and more
frequent bypasses of the treatment system is not expected to be a significant issue.
As mentioned previously, maximum capacity flow rate tests performed on 10 different Filterra®
systems demonstrated that the influent flow rate was maintained at or above the design flow rate
(100 to 140 inches/hour) for systems of varying age (recently activated to 3 years) and varying
maintenance periods (recently maintained to 2 years without maintenance) (Geosyntec 2008b).
Filterra® Bioretention Systems: Technical Basis for
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Figure 5. Matrix scatter plots showing relationships between percent removal and the
following variables: average hydraulic loading, average instantaneous hydraulic
loading, and peak hydraulic loading.
5. Conclusion
The Filterra® system design is based on bioretention technology and involves similar unit
treatment processes. The mulch and the media layer perform inert and reactive filtration
processes during storm events. The media layer also is expected to perform microbially-mediated
transformations, biological uptake and sequestration, bacterial inactivation processes, and
volatilization between storm events. In addition to microbially-mediated transformations and
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biological uptake and sequestration, soil processes such as evapotranspiration, surface
weathering, plant activity, and animal activity occur in and around the vegetation component and
its root system. These inter-storm processes support the retention of captured pollutants and the
preservation and regeneration of hydraulic function and pollutant removal capacity.
Filterra® systems filter stormwater at a high rate, allowing for a small footprint and providing a
standardized, easily installed and maintained design. Field flow rate tests performed on Filterra®
systems of varying age and varying maintenance periods resulted in a recommended design flow
rate of 140 inches per hour. Bench-scale experiments indicated that media flow rates greater than
100 inches/hour and significant removal of small particles is possible using Filterra® system
media. Five full-scale studies evaluating water quality treatment performance also found:
TSS efficiency ratio of 83 to 88 percent; median TSS effluent
concentration of less than 2.5 to 11.6 mg/L
Total phosphorus efficiency ratio of 9 to 70 percent; median TP effluent
concentration of 0.054 to 0.16 mg/L
TKN efficiency ratio of 40 percent; median TKN effluent concentration of
1.15 mg/L Total copper efficiency ratio of 33 to 77 percent; median total
copper effluent concentration of 0.0034 to 0.014 mg/L
Dissolved copper efficiency ratio of 48 percent; median dissolved copper
effluent concentration of 0.0033 mg/L
Total zinc efficiency ratio of 48 to 78 percent; median total zinc effluent
concentration of less than 0.02 to 0.102 mg/L
Dissolved zinc efficiency ratio of 55 percent; median dissolved zinc
effluent concentration of 0.082 mg/L
Oil and grease efficiency ratio of 59 percent; median oil and grease
effluent concentration of 2.9 mg/L
TPH efficiency ratio of 96 percent; median TPH effluent concentration of
1.2 mg/L
Effluent concentrations achieved in the full-scale studies were generally equal to or lower than
median effluent concentrations for the biofilter and media filter classes of BMPs reported in the
International Stormwater BMP Database. In addition, Filterra® systems showed statistically
significant removals for a broader range of pollutants than were shown for the biofilter and
media filter categories in the International Stormwater BMP Database.
Correlation analyses performed on effluent concentrations and computed percent removals for
TSS, dissolved copper, and dissolved zinc showed that system performance varied with influent
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concentration; however, these same analyses indicated that there is likely not a direct relationship
between system performance and hydraulic loading rate.
The semiannual maintenance schedule recommended by Contech Engineered Solutions. for east
coast installations and annual maintenance schedule for west coast installations appears to be
sufficient, based on results from maximum capacity flow rate tests demonstrating that the media
flow rate was maintained at or above 100 to 140 inches/hour for Filterra® systems of varying age
and varying maintenance periods. In industrial areas with heavy petroleum loading, the
maintenance frequency for the Filterra® system may need to be increased to maintain the flow
rate of the mulch layer protecting the filtration media.
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Filterra® Bioretention Systems: Technical Basis for
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Note: Filterra® Bioretention Systems became part of Contech Engineered Solutions, LLC in
September 2014.
DMAAREAPERVIOUSAREA (SF)IMPERVIOUSAREA (SF)TOTALAREA (SF)TOTALAREA (AC)EFFECTIVEIMPERVIOUSFRACTION*DMARUNOFFFACTORDMA AREAS x RUNOFF FACTORQ(BMP) REQUIRED(CFS)FILTERRA REQUIRED SURFACE AREA (SF)*V(BMP)REQUIRED (CF)PROVIDEDSURFACEAREA (SF)PROPOSED BMPSIZINGPROVIDED FLOW RATE (CFS)A 43587 59493 103080 2.37 0.704 0.50 51301 0.236 58 3420 60 FTBSV0610 0.243B 18798 38059 56857 1.31 0.769 0.56 32075 0.147 36 2139 48 FTBSV0608 0.194C 63078 43281 106359 2.44 0.585 0.40 42291 0.194 48 2820 48 FTBSV0608 0.194D 20212 55863 76075 1.75 0.814 0.62 46860 0.215 53 3124 60 FTIBC0610‐C 0.243E 21211 55578 76789 1.76 0.807 0.61 46655 0.214 53 3082 60 FTIBC0610‐C 0.243F 34063 66648 100711 2.31 0.763 0.56 56115 0.258 64 3744 72 FTBSV0612 0.292G 16363 29528 45891 1.05 0.750 0.54 24952 0.115 28 1664 36 FTBSV0606 0.146H 19515 32117 51632 1.19 0.735 0.53 27272 0.125 31 1819 36 FTBSV0606 0.146I 24532 37706 62238 1.43 0.724 0.52 32185 0.148 37 2146 48 FTBSV0608 0.194J 13796 29689 43485 0.99 0.778 0.57 24964 0.115 28 1665 36 FTBSV0606 0.146K 6813 31332 38145 0.88 0.875 0.69 26505 0.122 30 1767 36 FTBSV0606 0.146Q(BMP)/PROPRIETARY BMP FILTRATION RATE OF 175 IN/HR=REQUIRED SURFACE AREA*BASED ON AN INFITRATION RATE OF 175 IN/HR
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
A 103,080 Mixed Surface
Types 0.704 0.49768 51,301
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
103080 51301 0.20 0.236 0.243
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA A - BIOFILTRATION FILTERRA MODEL FTBSV0610
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
B 56,857 Mixed Surface
Types 0.769 0.56413 32,075
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
56857 32075 0.20 0.147 0.194
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA B - BIOFILTRATION FILTERRA MODEL FTBSV0608
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
C 106,359 Mixed Surface
Types 0.585 0.39763 42,291
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
106359 42291 0.20 0.194 0.195
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA C - BIOFILTRATION FILTERRA MODEL FTBSV0608
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
D 76,075 Mixed Surface
Types 0.814 0.61598 46,860
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
76075 46860 0.20 0.215 0.243
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA D - BIOFILTRATION FILTERRA MODEL FTIBCB0610-C
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
E 76,789 Mixed Surface
Types 0.807 0.60757 46,655
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
76789 46655 0.20 0.214 0.243
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA E - BIOFILTRATION FILTERRA MODEL FTIBCB0610-C
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
F 100,711 Mixed Surface
Types 0.763 0.55759 56,155
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
100711 56155 0.20 0.258 0.292
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA F - BIOFILTRATION FILTERRA MODEL FTBSV0612
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
G 45,891 Mixed Surface
Types 0.750 0.54372 24,952
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
45891 24952 0.20 0.115 0.146
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA G - BIOFILTRATION FILTERRA MODEL FTBSV0606
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
H 51,632 Mixed Surface
Types 0.735 0.5282 27,272
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
51632 27272 0.20 0.125 0.146
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA H - BIOFILTRATION FILTERRA MODEL FTBSV0606
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
I 62,238 Mixed Surface
Types 0.724 0.51713 32,185
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
62238 32185 0.20 0.148 0.194
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA I - BIOFILTRATION FILTERRA MODEL FTBSV0608
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
J 43,485 Mixed Surface
Types 0.778 0.57409 24,964
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
43485 24964 0.20 0.115 0.146
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA J - BIOFILTRATION FILTERRA MODEL FTBSV0606
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
Date
I = 0.20 in/hr
DMA
Type/ID
DMA Area
(square feet)
Post‐Project
Surface Type
(use pull‐down menu)
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Rainfall
Intensity
(in/hr)
Design Flow
Rate (cfs)
Proposed
Flow Rate
(cfs)
K 38,145 Mixed Surface
Types 0.875 0.69486 26,505
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
38145 26505 0.20 0.122 0.146
Notes:
Drainage Management Area Tabulation
Insert additional rows if needed to accommodate all DMAs draining to the BMP
Design Rainfall Intensity
TotalDMAs BMP Identification
BMP NAME / ID DMA K - BIOFILTRATION FILTERRA MODEL FTBSV0606
Must match Name/ID used on BMP Design Calculation Sheet
Design Rainfall Depth
Designed by K MIKAMI Case No 2022-0005
Company Project Number/Name Tentative Tract Map 38378
Santa Ana Watershed - BMP Design Flow Rate, QBMP
(Rev. 10-2011)
Legend:Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook )
Company Name Wilson Mikami Corporation 9/13/2022
1
SECTION (_____)
Filterra®Bioscape Configuration
Bioretention System Standard Specification
1.0 GENERAL
1.1 This item shall govern the furnishing and installation of the Filterra® Bioscape Bioretention
System by Contech Engineered Solutions LLC, complete and operable as shown and as
specified herein, in accordance with the requirements of the plans and contract documents.
1.2 Contractor shall furnish all labor, materials, equipment and incidentals necessary to install
and/or prepare the site for placement of the bioretention system, appurtenances and
incidentals in accordance with the Drawings and as specified herein.
1.3 Bioretention system shall utilize the physical, chemical and biological mechanisms of an
engineered biofiltration media, plant and microbe complex to remove pollutants typically
found in urban stormwater runoff. The treatment system shall be a fully equipped, pre-
constructed, drop-in-place unit designed for applications in the urban landscape to treat
contaminated runoff from impervious surfaces.
1.4 Bioretention plants shall be incorporated into the system with plant material extending into
the treatment zone of the engineered media at time of Activation.
1.5 The bioretention system shall be of a type that has been installed and in use for a minimum
of five (5) consecutive years preceding the date of installation of the system. The
Manufacturer shall have been, during the same consecutive five (5) year period, engaged in
the engineering design and production of systems deployed for the treatment of storm water
runoff and which have a history of successful production, acceptable to the Engineer of
Record and/or the approving Jurisdiction. The Manufacturer of the Filterra Bioscape
Bioretention System shall be, without exception:
Contech Engineered Solutions LLC
9025 Centre Pointe Drive
West Chester, OH, 45069
Tel: 1 800 338 1122
1.6 Applicable provisions of any Division shall govern work in this section.
1.7 Manufacturer or authorized supplier to submit shop drawings for bioretention system with
engineered biofiltration media and accessory equipment. Drawings shall include principal
dimensions, engineered biofiltration media placement, and location of piping.
1.7.1 Manufacturer or authorized supplier shall submit site preparation and installation
instructions to the contractor.
1.7.2 Manufacturer or authorized supplier shall submit Operations and Maintenance
Manual to the contractor.
2
1.7.3 Before installation of the bioretention system, Contractor shall obtain the
written approval of the Engineer of Record for the system drawings.
1.8 No product substitutions shall be accepted unless submitted 10 days prior to project bid date,
or as directed by the Engineer of Record. Submissions for substitutions require review and
approval by the Engineer of Record, for hydraulic performance, impact to project designs,
equivalent treatment performance, and any required project plan and report
(hydrology/hydraulic, water quality, stormwater pollution) modifications that would be
required by the approving jurisdictions/agencies. Contractor to coordinate with the Engineer
of Record any applicable modifications to the project estimates of cost, bonding amount
determinations, plan check fees for changes to approved documents, and/or any other
regulatory requirements resulting from the product substitution.
2.0 MATERIALS
2.1 All system components including engineered biofiltration media, underdrain stone, PVC
underdrain piping, and mulch must be included as part of the bioretention system and shall
be provided by Contech Engineered Solutions LLC.
2.1.1 Engineered biofiltration media shall consist of both organic and inorganic
components. Stormwater shall be directed to flow vertically through the media
profile, saturating the full media profile without downstream flow control.
2.1.2 Underdrain stone shall be of size and shape to provide adequate bridging
between the media and stone for the prevention of migration of fine particles.
Underdrain stone must also be able to convey the design flow rate of the system
without restriction and be approved for use in the Filterra Bioscape Bioretention
System by Contech Engineered Solutions LLC.
2.1.3 PVC Underdrain Piping shall be SDR35 with perforation pattern designed to
convey system design flow rate without restriction.
2.1.4 Mulch shall be double shredded wood or bark mulch approved for use with the
Filterra Bioscape Bioretention System by Contech Engineered Solutions LLC.
2.2 Vegetation shall be provided by the contractor and comply with the type and size required by
the site plans and shall be alive and free of obvious signs of disease.
2.3 Filterra Bioscape containment basin or structure shall be provided by the contractor in
accordance with the Engineer of Record site plans.
3.0 PERFORMANCE
3.1 Treatment Capabilities shall be verified via third-party report following either TAPE or TARP
protocols.
3.1.1 Engineered biofiltration media minimum treatment flow rate shall be 140”/hr.
The system shall be designed to ensure that high flow events shall bypass the
engineered biofiltration media preventing erosion and resuspension of
3
pollutants.
3.1.2 The system shall remove a minimum of 85% Total Suspended Solids (TSS).
3.1.3 The system shall remove a minimum of 62% Total Phosphorus (TP).
3.1.4 The system shall remove a minimum of 34% Total Nitrogen (TN).
3.2 Quality Assurance and Quality Control procedures shall be followed for all batches of
engineered biofiltration media produced. Engineered biofiltration media shall be certified by
the Manufacturer for performance and composition.
3.2.1 Media particle size distribution and composition shall be verified as per relevant
ASTM Standards.
3.2.2 Media pollutant removal performance shall be verified as per relevant ASTM
Standards as well as a minimum of one scientific method approved by the USEPA.
3.2.3 Media hydraulic performance shall be verified as per relevant ASTM Standards.
3.2.4 Media fertility shall be verified as per a minimum of one published scientific
method.
3.3 The Manufacturer shall ensure through third party full scale field testing of installed units that
the design flow rate of the system is not reduced over time. Studies shall be performed on a
minimum of 10 systems of various ages, maintenance frequencies, and land uses. At least
80% of the tested systems shall have been installed 2.5 or more years. At least 50% of the
systems shall have previous maintenance intervals greater than 2 times the manufacturer’s
recommendation.
4.0 EXECUTION
4.1 Contractor to prepare site for installation of the Filterra Bioscape Bioretention system as per
the “Filterra Bioscape Activation Guide for Contractors” provided by the Manufacturer.
4.1.1 Excavation of basin or installation of Cast-in-Place vault for the placement of
system components shall be completed by contractor
4.1.2 Inlet and outlet pipes shall be provided to the edge of the extents of the
Engineered Media for connection of underdrain during system installation by
contractor.
4.1.3 All bypass structures, piping, or other mechanisms should be installed and in
place by contractor prior to Filterra Bioscape System Activation.
4.2 The bioretention system shall not be placed in operation (activated) until the project site is
clean and stabilized (construction erosion control measures no longer required). The project
site includes any surface that contributes storm drainage to the system. All impermeable
4
surfaces shall be clean and free of dirt and debris. All catch basins, manholes and pipes shall
be free of dirt and sediment.
4.3 Activation consists of the placement of all system components identified in Section 2.1.
Activation must be provided by the contractor under supervision by Contech Engineered
Solutions, LLC, or a Contech certified 3rd Party Activation provider.
4.4 To ensure long term performance of the bioretention system, continuing annual
maintenance programs should be performed or purchased by the owner per the latest
Filterra Bioscape Bioretention System Operation and Maintenance manual.
SECTION A-ASLOTTED THROAT INLETSDR 35 OUTLET COUPLING CASTINTO PRECAST VAULT WALL(OUTLET PIPE LOCATION MAY VARY)ENERGY DISSIPATIONROCKSCURB AND GUTTER(NOT BY CONTECH)SEE FILTERRA BIOSCAPE VAULTCURB INLET DETAIL SHEET4"Ø - 6"Ø UNDERDRAINFLOWKIT (VARIES BY SIZE)PROVIDED BY CONTECH21" FILTERRA MEDIA, TYP.PROVIDED BY CONTECH6" UNDERDRAINSTONE LAYER, TYP.PROVIDED BY CONTECH3" MULCH LAYER, TYP.PROVIDED BY CONTECHSTREETPLANT PROVIDED BY CONTECH2"Ø IRRIGATION PORT,TYP. 3 PLACESGALVANIZED ANGLE NOSINGVAULT LENGTHPLAN VIEWSHORT SIDE INLETAA3'-9"
3'-5"4' CURB INLET (MAX)REFER TO OTHERDETAILS FORALTERNATE INLETSVAULT WIDTH*1'-0"*8"*1'-4"
*4"INLET SHAPING(NOT BY CONTECH)CURB(NOT BY CONTECH)UNDERDRAIN FLOWKIT*1'-0"SIDEWALK ELEVATIONIF APPLICABLE1"
3'-5" (3.42')
INV TO TOP
*8"
*2"
8"
MIN
1"
*1'-0"
2'-5" (2.42')
INV TO TOP
1"
3'-5" (3.42')
INV TO TOP
1"
1'-0" TYP
(1'-5" MAX)
1' MIN
BASIN DEPTH
ENERGY DISSIPATION ROCKSAT EACH INLET6"Ø MAX SDR 35INLET COUPLER(CAST-IN)1" TYP
2'-6"ENERGY DISSIPATION ROCKSAT EACH INLETCURB AND GUTTER(NOT BY CONTECH)SEE FILTERRA BIOSCAPE VAULT CURBINLET DETAIL SHEET18" GI INLET (CAST-IN)STREETENERGY DISSIPATION ROCKSPLANT PROVIDED BY CONTECHPLANT PROVIDED BY CONTECHPLANT PROVIDED BY CONTECHSECTION A-AGREEN INFRASTRUCTURE INLET - TOP FLUSH WITH TOP OFCURB, NOT INTENDED FOR SIDEWALK APPLICATIONSSECTION A-ABASIN - CURB INLET OR PIPE INLETS OPTIONALSECTION A-APIPE INLETFTBSV CONFIGURATION(OPTIONS: BASIN "-B", GREEN INFR. INLET "-I", PIPE INLET "-P", SLOTTED THROAT INLET "-T")MEDIABAY SIZEVAULT SIZE(L x W)LONG SIDE INLETDESIGNATIONSHORT SIDE INLETDESIGNATIONAVAILABILITYOUTLETPIPE DIAMIN. NO. OF INLETPIPES (-P ONLY)4 x 44 x 4FTBSV0404FTBSV0404ALL4" SDR 3516 x 46 x 4FTBSV0604FTBSV0406N/A CA4" SDR 3516.5 x 46.5 x 4FTBSV06504FTBSV04065CA ONLY4" SDR 3517.83 x 4.57.83 x 4.5FTBSV078045FTBSV045078DE,MD,NJ,PA,VA.WVONLY4" SDR 3518 x 48 x 4FTBSV0804FTBSV0408N/ADE,MD,NJ,PA,VA,WV4" SDR 3516 x 66 x 6FTBSV0606FTBSV0606ALL4" SDR 3518 x 68 x 6FTBSV0806FTBSV0608ALL4" SDR 35110 x 610 x 6FTBSV1006FTBSV0610ALL6" SDR 35212 x 612 x 6FTBSV1206FTBSV0612ALL6" SDR 35213 x 713 x 7FTBSV1307FTBSV0713ALL6" SDR 35214 x 814 x 8FTBSV1408†N/AALL6" SDR 35316 x 816 x 8FTBSV1608†N/AN/A OR,WA6" SDR 35315 x 915 x 9FTBSV1509†N/AOR,WA ONLY6" SDR 35318 x 818 x 8FTBSV1808†N/ACALL CONTECH6" SDR 35320 x 820 x 8FTBSV2008†N/ACALL CONTECH6" SDR 35422 x 822 x 8FTBSV2208†N/ACALL CONTECH6" SDR 354†UTILIZES (2) CURB OPENINGS WITH MIN 1' SPACINGN/A = NOT AVAILABLEI:\STORMWATER\COMMOPS\54 FILTERRA\40 STANDARD DRAWINGS\FTBSV - FILTERRA BIOSCAPE VAULT OFFLINE\LAYOUT DETAILS\DWG\FTBSV - FILTERRA BIOSCAPE VAULT OFFLINE CONFIG DTL.DWG 12/22/2020 2:50 PM
FILTERRA BIOSCAPE VAULT STANDARD OFFLINE (FTBSV)CONFIGURATION DETAILThe design and information shown on this drawing is provided as a service to the project owner, engineer and contractor by Contech Engineered Solutions LLC or one of its affiliated companies ("Contech"). Neither this drawing, nor any part thereof, may be used, reproduced or modified in any mannerwithout the prior written consent of Contech. Failure to comply is done at the user's own risk and Contech expressly disclaims any liability or responsibility for such use. If discrepancies between the supplied information upon which the drawing is based and actual field conditions are encountered as sitework progresses, these discrepancies must be reported to Contech immediately for re-evaluation of the design. Contech accepts no liability for designs based on missing, incomplete or inaccurate information supplied by others.INTERNAL PIPECONFIGURATION MAY VARYDEPENDING ON VAULT SIZE.DIMENSIONS PRECEDED BY " * " ARE CRITICAL AND MAY NOT BE MODIFIED WITHOUT CONSULTING CONTECH5670 Greenwood Plaza Blvd., Suite 530, Greenwood Village, CO 80111800-526-3999 303-796-2233 303-796-2239 FAXwww.ContechES.comTHIS PRODUCT MAY BE PROTECTED BY ONE OR MORE OFTHE FOLLOWING U.S. PATENTS: 6,277,274; 6,569,321;7,625,485; 7,425,261; 7,833,412; RELATED FOREIGN PATENTS.®AS WITH ALL OPEN TOP BIORETENTION SYSTEMS, FILTERRA BIOSCAPE IS OPEN TO THE ATMOSPHERE WITH A MEDIASURFACE RECESSED BELOW FINISHED GRADE. CONTRACTOR OR OWNER IS RESPONSIBLE FOR PROVIDING ANYREQUIRED SAFETY MEASURES AROUND SYSTEM PERIMETER. TO MAINTAIN AESTHETICS, REMOVAL OF HEAVYSTORMWATER DEBRIS MAY BE NECESSARY BETWEEN REGULAR FILTERRA SYSTEM MAINTENANCE EVENTS.
FTBSV - IGREEN INFRASTRUCTURE INLET - TOP FLUSHWITH TOP OF CURB, NOT INTENDED FORSIDEWALK APPLICATIONSFTBSVSLOTTED THROAT INLET - TOP EXTENDS 4"ABOVE CURB FOR ADJACENT SIDEWALKSFTBSV - BBASIN - CURB INLET OR PIPE INLET OPTIONALFTBSV - PPIPE INLETALTERNATE PIPEINLET OPENINGI:\COMMON\CAD\TREATMENT\54 FILTERRA\40 STANDARD DRAWINGS\FTBSV - BIOSCAPE VAULT OFFLINE\LAYOUT DETAILS\DWG\IN PROCESS\FTBSV - FILTERRA BIOSCAPE VAULT OFFLINE CONFIG DTL.DWG 11/3/2020 9:50 AM
FILTERRA BIOSCAPE VAULT STANDARD OFFLINE (FTBSV)SITE LAYOUT DETAILThe design and information shown on this drawing is provided as a service to the project owner, engineer and contractor by Contech Engineered Solutions LLC or one of its affiliated companies ("Contech"). Neither this drawing, nor any part thereof, may be used, reproduced or modified in any mannerwithout the prior written consent of Contech. Failure to comply is done at the user's own risk and Contech expressly disclaims any liability or responsibility for such use. If discrepancies between the supplied information upon which the drawing is based and actual field conditions are encountered as sitework progresses, these discrepancies must be reported to Contech immediately for re-evaluation of the design. Contech accepts no liability for designs based on missing, incomplete or inaccurate information supplied by others.5670 Greenwood Plaza Blvd., Suite 530, Greenwood Village, CO 80111800-526-3999 303-796-2233 303-796-2239 FAXwww.ContechES.comTHIS PRODUCT MAY BE PROTECTED BY ONE OR MORE OFTHE FOLLOWING U.S. PATENTS: 6,277,274; 6,569,321;7,625,485; 7,425,261; 7,833,412; RELATED FOREIGN PATENTS.®
INLET SHAPING(NOT BY CONTECH)CURB(NOT BY CONTECH)AAVAULT WIDTHPLAN VIEWSECTION A-A(SLOTTED THROAT INLET - TOP EXTENDS 4"ABOVE CURB FOR ADJACENT SIDEWALKS)VAULT LENGTH6"Ø - 10"Ø SDR 35OUTLET COUPLINGCAST INTOPRECAST VAULTWALL (OUTLET PIPELOCATION MAYVARY)ENERGY DISSIPATIONROCKSCURB AND GUTTER (NOT BY CONTECH)SEE FILTERRA BIOSCAPE VAULT CURBINLET DETAIL SHEET4"Ø - 6"Ø UNDERDRAINFLOWKIT (VARIES BY SIZE)PROVIDED BY CONTECH21" FILTERRA MEDIA, TYP.PROVIDED BY CONTECH6" UNDERDRAINSTONE LAYER, TYP.PROVIDED BY CONTECH3" MULCH LAYER, TYP.PROVIDED BY CONTECH6"Ø - 10"Ø BYPASSINLET GRATE4' CURB INLET (MAX.)REFER TO OTHER DETAILS FORALTERNATE INLET OPTIONS4'-2"STREETPLANT PROVIDED BY CONTECH2"Ø IRRIGATION PORT,TYP. 3 PLACESGALVANIZED ANGLE NOSING*4"
3'-10"
*1'-0"*1'-5"*1'-9"SIDEWALK/CURB ELEVATION(IF APPLICABLE)1"
3'-10" (3.83')
INV TO TOP
*8"
*2"
8"
MIN.
1"
*1'-5"
2'-5" (2.42')
INV. TO TOP
1"1"
*1'-5"1'-5" MIN.
BASIN DEPTH
ENERGY DISSIPATION ROCKSAT EACH INLET6"Ø MAX. SDR 35INLET COUPLER(CAST-IN)1" TYP.
2'-6" (2.5')ENERGY DISSIPATIONROCKS AT ALL INLETS ORPERIMETER, AS APPLICABLECURB AND GUTTER(NOT BY CONTECH)SEE FILTERRA BIOSCAPE VAULTCURB INLET DETAIL SHEET18" WIDE GI INLET (CAST-IN)STREETENERGY DISSIPATION ROCKSPLANT PROVIDED BY CONTECHPLANT PROVIDED BY CONTECHPLANT PROVIDED BY CONTECHSECTION A-AGREEN INFRASTRUCTURE INLET - TOP FLUSH WITH TOP OFCURB, NOT INTENDED FOR SIDEWALK APPLICATIONSSECTION A-ABASIN - CURB INLET OR PIPE INLETS OPTIONALSECTION A-APIPE INLETFTBSVIB CONFIGURATION(OPTIONS: BASIN "-B", GREEN INFRASTRUCTURE INLET "-I", PIPE INLET "-P", SLOTTED THROAT INLET "-T")MEDIABAY SIZEVAULTSIZE(L x W)LONG SIDEINLETDESIGNATIONSHORT SIDEINLETDESIGNATIONAVAILABILITYMAX.OUTLET /BYPASSPIPE DIA.MAX.BYPASSFLOW(CFS)UNDERDRAINPIPE DIA.(PERF)MIN. NO.OF INLETPIPES (-PONLY)4 x 44 x 4FTBSVIB0404FTBSVIB0404ALL6" SDR 351.424" SDR 3516 x 46 x 4FTBSVIB0604FTBSVIB0406N/A CA8" SDR 351.894" SDR 3516.5 x 46.5 x 4FTBSVIB06504FTBSVIB04065CA ONLY8" SDR 351.894" SDR 3517.83 x 4.57.83 x 4.5FTBSVIB078045FTBSVIB045078DE,MD,NJ,PA,VA.WVONLY8" SDR 351.894" SDR 3518 x 48 x 4FTBSVIB0804FTBSVIB0408N/ADE,MD,NJ,PA,VA,WV8" SDR 351.894" SDR 3516 x 66 x 6FTBSVIB0606FTBSVIB0606ALL8" SDR 351.894" SDR 3518 x 68 x 6FTBSVIB0806FTBSVIB0608ALL10" SDR 352.374" SDR 35110 x 610 x 6FTBSVIB1006FTBSVIB0610ALL10" SDR 352.376" SDR 35212 x 612 x 6FTBSVIB1206FTBSVIB0612ALL10" SDR 352.376" SDR 35213 x 713 x 7FTBSVIB1307FTBSVIB0713ALL10" SDR 352.376" SDR 35214 x 814 x 8FTBSVIB1408†N/AALL10" SDR 352.376" SDR 35316 x 816 x 8FTBSVIB1608†N/AN/A OR, WA10" SDR 352.376" SDR 35315 x 915 x 9FTBSVIB1509†N/AOR, WA ONLY10" SDR 352.376" SDR 35318 x 818 x 8FTBSVIB1808†N/ACALL CONTECH10" SDR 352.376" SDR 35320 x 820 x 8FTBSVIB2008†N/ACALL CONTECH10" SDR 352.376" SDR 35422 x 822 x 8FTBSVIB2208†N/ACALL CONTECH10" SDR 352.376" SDR 354†UTILIZES (2) CURB OPENINGS WITH MIN 1' SPACINGN/A = NOT AVAILABLEI:\STORMWATER\COMMOPS\54 FILTERRA\40 STANDARD DRAWINGS\FTBSVIB - FILTERRA BIOSCAPE VAULT INTERNAL BYPASS\LAYOUT DETAILS\DWG\FTBSVIB - FILTERRA BIOSCAPE VAULT INTERNAL BYPASS CONFIG DTL UPD.DWG 12/22/2020 2:45PM
FILTERRA BIOSCAPE VAULT INTERNAL BYPASS(FTBSVIB)CONFIGURATION DETAILThe design and information shown on this drawing is provided as a service to the project owner, engineer and contractor by Contech Engineered Solutions LLC or one of its affiliated companies ("Contech"). Neither this drawing, nor any part thereof, may be used, reproduced or modified in any mannerwithout the prior written consent of Contech. Failure to comply is done at the user's own risk and Contech expressly disclaims any liability or responsibility for such use. If discrepancies between the supplied information upon which the drawing is based and actual field conditions are encountered as sitework progresses, these discrepancies must be reported to Contech immediately for re-evaluation of the design. Contech accepts no liability for designs based on missing, incomplete or inaccurate information supplied by others.INTERNAL PIPE CONFIGURATION MAYVARY DEPENDING ON VAULT SIZE.800-338-1122 513-645-7000 513-645-7993 FAX9025 Centre Pointe Dr., Suite 400, West Chester, OH 45069www.ContechES.comTHIS PRODUCT MAY BE PROTECTED BY ONE OR MORE OFTHE FOLLOWING U.S. PATENTS: 6,277,274; 6,569,321;7,625,485; 7,425,261; 7,833,412; RELATED FOREIGN PATENTS.®DIMENSIONS PRECEDED BY " * " ARE CRITICAL AND MAY NOT BE MODIFIED WITHOUT CONSULTING CONTECHAS WITH ALL OPEN TOP BIORETENTION SYSTEMS, FILTERRA BIOSCAPE IS OPEN TO THEATMOSPHERE WITH A MEDIA SURFACE RECESSED BELOW FINISHED GRADE. CONTRACTOR OROWNER IS RESPONSIBLE FOR PROVIDING ANY REQUIRED SAFETY MEASURES AROUND SYSTEMPERIMETER. TO MAINTAIN AESTHETICS, REMOVAL OF HEAVY STORMWATER DEBRIS MAY BENECESSARY BETWEEN REGULAR FILTERRA SYSTEM MAINTENANCE EVENTS.
FTBSVIB - IGREEN INFRASTRUCTURE INLET - TOPFLUSH WITH TOP OF CURB, NOT INTENDEDFOR SIDEWALK APPLICATIONSFTBSVIBSLOTTED THROAT INLET - TOP EXTENDS 4"ABOVE CURB FOR ADJACENT SIDEWALKSFTBSVIB - BBASIN - CURB INLET OR PIPE INLET OPTIONALFTBSVIB - PPIPE INLETALTERNATE PIPEINLET OPENINGI:\COMMON\CAD\TREATMENT\54 FILTERRA\40 STANDARD DRAWINGS\IN PROCESS FTBSVIB - BIOSCAPE VAULT INTERNAL BYPASS\LAYOUT DETAILS\DWG\FTBSVIB - FILTERRA BIOSCAPE VAULT INTERNAL BYPASS CONFIG DTL.DWG 11/3/2020 10:41 AM
FILTERRA BIOSCAPE VAULT INTERNAL BYPASS(FTBSVIB)SITE LAYOUTSThe design and information shown on this drawing is provided as a service to the project owner, engineer and contractor by Contech Engineered Solutions LLC or one of its affiliated companies ("Contech"). Neither this drawing, nor any part thereof, may be used, reproduced or modified in any mannerwithout the prior written consent of Contech. Failure to comply is done at the user's own risk and Contech expressly disclaims any liability or responsibility for such use. If discrepancies between the supplied information upon which the drawing is based and actual field conditions are encountered as sitework progresses, these discrepancies must be reported to Contech immediately for re-evaluation of the design. Contech accepts no liability for designs based on missing, incomplete or inaccurate information supplied by others.800-338-1122 513-645-7000 513-645-7993 FAX9025 Centre Pointe Dr., Suite 400, West Chester, OH 45069www.ContechES.comTHIS PRODUCT MAY BE PROTECTED BY ONE OR MORE OFTHE FOLLOWING U.S. PATENTS: 6,277,274; 6,569,321;7,625,485; 7,425,261; 7,833,412; RELATED FOREIGN PATENTS.®
Filterra Bioscape Plant List - Southern CaliforniaCommon Name1,2,8Latin Name Plant Type SunHardiness RangeMature Height5Mature Spread5Sizing7Availability9NativityAcacia, SweetAcacia smalliiDeciduous Full Sun 9A - 11 15' - 25' 15' - 25' Tree SoCAW-US, Central AmericaBeautyberryCallicarpa AmericanaDeciduous Partial Shade to Full Sun 7A - 10B 4' - 8' 6' - 7' LMA, NW, SE, SC, NoCA, SoCASE-US, S-USBlue Palo VerdeParkinsonia floridumDeciduous Full Sun 8A - 11 10' - 20' 15' XL NW, SC, NoCA, SoCA US-CACeanothus, Big-podCeanothus megacarpusDeciduous Partial Shade to Full Sun 7A - 10B 4' - 8' 6' - 7' L SoCA US-CAChokeberry, BlackAronia melanocarpaDeciduous Full Shade to Full Sun 3B – 8B 3’ – 6’ 4’ – 6’ MGl, MA, NE, NW, SE, NoCA, SoCA, E-CanE-Can, E-USChokeberry, RedAronia arbutifolia Deciduous Partial Shade to Full Sun 4B – 9A 6’ – 10’ 4’ – 6’ MGL, MA, NE, NW, SE, NoCA, SoCAE-USCoyote BrushBaccharis pilularis ssp. ConsanguineaDeciduous Partial Shade to Full Sun 5A - 10A 4' - 6' 6' - 8' L NoCA, SoCA US-HICrabapple, AmericanMalus coronariaDeciduous Full Sun 3B - 8A 15’ - 25’ 10’ - 25’ TreeGL, MA, NE, NW, SE, NoCA, SoCAMidwest-USCrape MyrtleLagerstoemia indicaDeciduous Full Sun 7A - 9A 15' - 25' 15' - 25' Tree MA, SE, NoCA, SoCA AsiaElderberry, AmericanSambucus canadensisDeciduous Partial Shade to Full Sun 4A – 9B 10’ – 15’ 6’ – 10’ LGL, GP, MA, NW, SC, SE, NoCA, SoCAE-USElderberry, MexicanSambucus mexican 'Blue Elderberry'Deciduous Partial Shade to Full Sun 7B - 10A 8' - 15' 15' XL NoCA, SoCA W-USFour-wing SaltbushAtriplex canescensDeciduous Partial Shade to Full Sun 8A - 11 4' - 6' 10' L SC, SoCAW-US, Midwest-USFringe Tree, ChineseChionanthus retususDeciduous Full Shade to Full Sun 5B - 9A 15’ - 25’ 10’ - 15’ TreeGL, MA, NW, NE, SC, SE, NoCA, SoCAAsiaHolly, WinterberryIlex verticillataDeciduous Partial Shade to Full Sun 3B – 9A 6’ – 10’ 8’ – 15’ LGL, MA, NW, SC, SE, NoCA, SoCA, E-CanE-US, E-CanLilac, DwarfSyringa meyeriDeciduous Full Sun 3B – 8A 5’ – 8’ 8’ – 10’ LGL, MA, NE, NW, SC, SE, NoCA, SoCAAsiaMagnolia, GalaxyMagnolia x ‘Galaxy’Deciduous Partial Shade to Full Sun 5A - 8B 15’ - 20’ 15’ - 25’ TreeGL, MA, NE, NW, SC, SE, NoCA, SoCAAsiaMagnolia, SaucerMagnolia x soulangianaDeciduous Partial Shade to Full Sun 5A - 9A 15’ - 25’ 15’ - 25’ TreeMA, NE, NW, SC, SE, NoCA, SoCAAsiaPlum, MexicanPrunus mexicanaDeciduous Partial Shade to Full Sun 6B - 8A 15' - 25' 15' - 25' TreeSoCA S-USPlum, PurpleleafPrunus cerasiferaDeciduous Full Sun 5B - 8A 15’ - 25’ 15’ - 25’ TreeGL, MA, NE, NW, SE, NoCA, SoCAEurope, AsiaPlum, Purpleleaf 'Krauter Vesuvius'Prunus cerasifera 'Krauter Vesuvius'Deciduous Full Sun 5B - 8A 15’ - 25’ 15’ - 25’ Tree NW, SoCA Europe, AsiaRedbud, EasternCercis canadensisDeciduous Partial Shade to Full Sun 4B - 9A 15’ - 25’ 15’ - 25’ TreeGL, GP, MA, NE, NW, SE, NoCA, SoCAE-US, S-US, MexicoRedbud, MexicanCercis canadensisDeciduous Partial Shade to Full Sun 6B - 8A 15' - 20' 10' - 15' XL SC, SoCAE-US, S-US, MexicoSugar Bush, Sugar SumacRhus ovataDeciduous Partial Shade to Full Sun 8A - 11 8' - 15' 10' L NW, NoCA, SoCA SW-USSweetshrubCalycanthus floridusDeciduous Full Shade to Full Sun 5B – 10A 6’ – 10’ 6’ – 12’ LGL, MA, NW, SC, SE, NoCA, SoCAE-USWillow, DesertChilopsis linearisDeciduous Full Sun 7A - 11 15' - 25' 15' - 25' Tree NoCA, SoCA SW-US, Mexico1
Common Name1,2,8Latin Name Plant Type SunHardiness RangeMature Height5Mature Spread5Sizing7Availability9NativityAcacia, Bailey's PurpleAcacia baileyana 'Purpurea'Evergreen Full Sun 10B - 11 15' - 20' 20' - 30' Tree NoCA, SoCA AustraliaAcacia, CatclawAcacia greggiEvergreen Full Sun 9A - 11 15' - 25' 15' - 20' Tree SoCA SW-USAfter Dark PeppermintAgonis flexuosa "Jervis Bay Afterdark'Evergreen Full Sun 10 - 11 15' - 18' 10' - 15' XL SoCA AustraliaBottlebrush, LemonCallistemon citrinusEvergreen Full Sun 9A - 11 10' - 15' 10' - 15' XL SE, SoCA AustraliaCamellia, JapaneseCamellia japonicaEvergreen Partial Shade to Full Sun 7A - 9A 10' - 15' 6' - 10' LMA, NW, SC, SE, NoCA, SoCAAsiaGold Medallion Shrub FormCassia leptophyllaEvergreen Partial Shade 7A - 9A 10' - 15' 6' - 10' L SoCA South AmericaHawthorn, IndianRaphiolepsis indicaEvergreen Partial Shade to Full Sun 8A - 11 4' - 10' 3' - 10' LNW, SC, SE, NoCA, SoCAAsiaHawthorn, YeddaRaphiolepsis umbellata 'Majestic Beauty'Evergreen Partial Shade to Full Sun 8A - 10A 8' - 10' 8' - 10' L SC, SE, NoCA, SoCA AsiaHolly, ChineseIlex cornutaEvergreen Partial Shade to Full Sun 7A - 9A 15' - 25' 15' - 25' TreeMA, NE, NW, SE, NoCA, SoCAAsiaHolly, Foster’sIlex x attenuata ‘Fosteri’Evergreen Partial Shade to Full Sun 6A - 9A 20’ - 25’ 6’ - 10’ LMA, NE, NW, SC, SE, NoCA, SoCASE-USHolly, InkberryIlex glabraEvergreen Partial Shade to Full Sun 6A – 9A 4’ – 8’ 2’ – 4’ SMA, NE, SC, SE, NoCA, SoCA, E-CanE-US, E-CanHolly, Nellie StevensIlex xEvergreen Partial Shade to Full Sun 6A - 9A 15’ - 25’ 6’ - 10’ LMA, NE, NW, SC, SE, NoCA, SoCAEurope/Asia-DevelopedHolly, San JoseIlex x aquipernyiEvergreen Full Shade to Full Sun 5B - 9A 15' - 20' 10' - 15' XL NW, SC, NoCA, SoCAEurope/Asia-DevelopedHolly, YauponIlex vomitoriaEvergreen Full Shade to Full Sun 7A - 10A 15' - 18' 10' - 15' XLMA, NW, SC, SE, NoCA, SoCASE-USJuniper, CaliforniaJuniperus californicaEvergreen Partial Shade to Full Sun 8A - 10A 8' - 12' 6' L SC, NoCA, SoCA US-CALemon Scented TeaLeptospermum petersoniiEvergreen Full Sun 9B - 10 12 - 20' 8' - 12' XL SoCA AustraliaManzanita, BigberryArctostaphylos glaucaEvergreen Partial Shade to Full Sun 7A - 11 6' - 15' 8' - 10' L NoCA, SoCA US-CAManzanita, Del MarGrandulosa ssp. CrassifoliaEvergreen Partial Shade to Full Sun 8A - 11 6' - 15' 8' - 10' L SC, NoCA, SoCA US-CAManzanita, EastwoodArctostaphylos glandulosaEvergreen Partial Shade to Full Sun 8A - 11 3' - 6' 5' - 6' M SC, NoCA, SoCA US-CAManzanita, Howard McMinnArctostaphylos densifloraEvergreen Partial Shade to Full Sun 8A - 11 4' - 6' 6' M SC, NoCA, SoCA US-CAMock OrangePittosporum tobiraEvergreen Partial Shade to Full Sun 8A - 11 6' - 10' 10' - 15' XL NW, SC, NoCA, SoCA AsiaNarrowleaf PittosporumPittosporum PhillyreoidesEvergreen Partial Shade to Full Sun 9A - 11 20' - 30' 15' - 20' TreeNoCA, SoCA US-CAOlive, FruitlessOlea europaea 'Fruitless'Evergreen Full Sun 8A - 11 15' - 25' 15' - 20' Tree SoCA Europe, AsiaOsmanthus, SweetOsmanthus , fragramsEvergreen Partial Shade to Full Sun 7B - 9A 15' - 25' 15' - 25' TreeSoCA AsiaPalm, MiraguamaCoccothrinax miraguamaEvergreen Partial Shade to Full Sun 9B-11 15' - 20’ 6' - 8’ L SoCA Caribbean2
Common Name1,2,8Latin Name Plant Type SunHardiness RangeMature Height5Mature Spread5Sizing7Availability9NativityPalm, Pacific/Fiji FanPritchardia pacificaEvergreen Partial Sun 10B-11 10' - 20’ 5' -10’ L SoCA OceaniaPalm, PeaberryThrinax morrisiiEvergreen Partial Sun to Full Sun 10B-11 15' - 20’ 6' - 8’ L SoCAUS-FL, CaribbeanPalm, Sea ThatchThrinax radiateEvergreen Partial Sun to Full Sun 10B-11 15' - 20’ 8' - 10’ L SoCAUS-FL, CaribbeanPalm, ThurstonPritchardia thurstoniiEvergreen Full Sun 10B-11 15' - 25’ 8’ L SoCA OceaniaPalm, WindmillTrachycarpus fortuneiEvergreen Partial Sun to Shade 8 - 10 10' - 20’ 6' - 10’ L SoCA AsiaPalmetto, DwarfSabal minorEvergreen Partial Sun to Full Sun 8B - 11 4' - 6' 3' - 6' M NoCA, SoCA SE-USPittosporum KohuhuPittosporum tenuifoliumEvergreen Partial Shade to Full Sun 9A-10B 12' - 20’ 6' - 15’ XL NoCA, SoCA OceaniaPowderpuffCalliandra haematocephalaEvergreen Partial Shade to Full Sun 9B-11 10' - 15’ 10' - 15’ XL SoCASouth AmericaPowderpuff, PinkCalliandra surinamensisEvergreen Partial Shade to Full Sun 10A-11 12' - 15’ 12' - 15’ XL SoCA South AmericaStrawberry TreeArbutus unedoEvergreen Partial Shade to Full Sun 7B - 11 15' - 25' 15' - 25' TreeSC, SE, NoCA, SoCA EuropeSumac, Lemonade BerryRhus, integrifoliaEvergreen Partial Shade to Full Sun 9B-11 6' - 10’ 10' - 15’ XL SoCA US-CAToyonHeteromeles arbutifoliaEvergreen Partial Shade to Full Sun 8B-10B 8' - 15’ 15’ XL SC, NoCA, SoCA W-USTrumpet TreeTabebuia impetiginosaEvergreen Full Sun 9B-11 15' - 20’ 15' - 20’ Tree SoCACentral America, South AmericaWax Myrtle, PacificMyrica californicaEvergreen Partial Shade to Full Sun 7B - 11 15' - 25' 15' - 25' TreeNW, SC, NoCA, SoCA W-USYellow-wood, Long LeafedPodocarpus henkeliiEvergreen Partial Shade to Full Sun 9A-11 15' - 25’ 8' - 15’ XL SoCA AfricaBerkeley SedgeCarex divulsaGrass/Sedge Partial Shade to Full Sun 5 - 9 12" - 18" 12" - 18" XS NW, NoCA, SoCA EuropeBlue Grama GrassBouteloua gracilisGrass/Sedge Partial Sun to Full Sun 4 - 9 12" - 36" 24" - 36" SGP, SC, GL, NoCA, SoCAW-USBlue Moor GrassSesleria caeruleaGrass/Sedge Partial Sun to Full Sun 5 - 9 12" 12" - 24" XS NoCA, SoCAEuropeBlue Oat GrassHelictotrichon sempervirensGrass/Sedge Full sun 4 – 8 20” – 24” 20” – 40” XSGL, MA, NW, NoCA, SoCAEuropeDeer GrassMuhlenbergia rigensGrass/Sedge Partial Sun to Full Sun 5 - 11 48" - 60" 48" - 72" M NoCA, SoCA US-CAFlax LilyDianella caeruleaGrass/Sedge Partial Sun to Full Sun 7 - 11 12"- 24" 12" - 24" XS NoCA, SoCA, SE AustraliaFoothill NeedlegrassNasella lepidaGrass/Sedge Partial Sun to Full Sun 6 - 9 12" - 36" 12" - 60" S NoCA, SoCA US-CANyalla Mat RushLomandra longifolia NyallaGrass/Sedge Partial Shade to Full Sun 7 - 11 36" - 48" 36" - 48" S NoCA, SoCA AustraliaSan Diego SedgeCarex spissaGrass/SedgePartial Shade to Partial Sun6 - 10 36" - 72" 24" - 60" S NoCA, SoCA SW-USTropic Belle Mat RushLomandra hystrix TropicbelleGrass/Sedge Partial Shade to Full Sun 8 - 11 24" - 36" 24" - 48" S SoCA Australia3
Common Name1,2,8Latin Name Plant Type SunHardiness RangeMature Height5Mature Spread5Sizing7Availability9NativityWire GrassJuncus patensGrass/Sedge Partial Shade to Full Sun 6 - 10 12" - 24" 12" - 24" XS NW, NoCA, SoCA US-CANotes:7. All Filterra vault systems incorporate a ponding depth ranging from 12"-36" between finished grade and media surface. For systems with more than 18" from finshed grade to media (FTIBC, FTIBP, FTPD, etc), Contech recommends choosing a species with "Sizing" noted as "XL" or "Tree".5. Mature height and spread do not reflect plant size at planting / system activation. Contact Contech for information on available sizes at activation. 1. The species listed are drought tolerant and have applicability to bioretention due to shallow root zones.2. The species highlighted in green are typically more readily available in the noted regions as the listed species or another similar cultivar.3. This list is subject to availability and Contech reserves the right to make appropriate substitutions when necessary. 4. For species not listed, please contact Contech for suitability.6. Contech promotes the use of non-invasive species in Filterra systems, and has made efforts to maintain a plant list free of invasives. However, always check with local sources, as some species listed (even natives) may be invasive in some regions and not others. 8. The species highlighted in orange are available for an additional charge of $250 per plant required.9. Availability Key: GL=Great Lakes; GP=Great Plains; MA=Mid-Atlantic; NE=Northeast; NW=Northwest; SW=Southwest; SE=Southeast; SC=South Central; NoCA=Northern CA; SoCA=Southern CA; E-Can=Eastern Canada; W-Can=Western Canada4
- 35 -
Appendix 7: Hydromodification
Supporting Detail Relating to Hydrologic Conditions of Concern
Sedco Master Plan of Drainage Line D Storm Drain Plans Drawings No. 3-119 Depicting
Discharge point for Storm Drain Line from Project Site with direct discharge into Lake Elsinore
WILSON MIKAMI
CORPORATION
PARK
WILSON MIKAMI
CORPORATION
- 36 -
Appendix 8: Source Control
Pollutant Sources/Source Control Checklist
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Appendix 9: O&M
Operation and Maintenance Plan and Documentation of Finance, Maintenance and Recording Mechanisms
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Appendix 10: Educational Materials
BMP Fact Sheets, Maintenance Guidelines and Other End-User BMP Information