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Home My WebLink AboutTR 31920 GEOTECHNICAL REPORT UPDATE SoilWorks Earth Sciences Group 350 Fischer Avenue Cast& Mesa, CA 42626 T: 714-668-5600 www.sollworksrnc.corn McMillin Land Development October 5, 2012 P.O. Box 85104 Project No. 118-003-01 San Diego, CA 92106 Attention: Mr. Don Mitchell Senior Vice President Subject: Geotechnical Report Update Parcels 2, 3, 5, 7, 8, and 12 Tract 31920 Summerly Development City of Lake Elsinore, California References: See attached List of Selected References Dear Mr. Mitchell: Pursuant to your request, SoilWorks, Inc. has reviewed the referenced documents prepared by Neblett & Associates, Inc., the former geotechnical of record for the Summerly Development site (Tract 31920), and has prepared this letter providing updated geotechnical recommendations for the design and construction of residence foundations for the subject parcels. Included in this letter are general site development recommendations for appurtenant construction, site drainage landscaping and irrigation. Project Background Rough grading for Parcels 2, 3, 5, 7 and 8 were performed as part of the mass grading for the Phase 1 Summerly Development in 2005-2006 under the observation and testing of former Neblett & Associates, Inc. (NA) and reported in Reference Nos. 4 through 9. During this same period, rough grading for Parcel 12 (previously identified as Parcel 13) was performed as part of the mass grading for the Phase 2 Summerly Development SW McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 2 of 21 Summerly Development City of Lake Elsinore, California (see Reference No. 10). The locations of these parcels within the Summerly Development site are shown on Figure 1, attached. Mass grading for these parcels included the removal of near surface weathered, disturbed or otherwise unsuitable materials and placement of approximately 13 to 22 feet (maximum) of engineered compacted fill beneath respective parcels to achieve rough grade elevations. Preliminary foundation recommendations for planned residences on the subject parcels were provided by NA in the referenced reports and included conventional continuous and spread footings with floor slabs on grade and optional post-tensioned slab foundations. In late 2010 - early 2011, the pads within parcel 5 were reconditioned under the observation and testing of this firm and recertified for construction. However the lots within this parcel, as well as the lots on the remaining subject parcels, remain undeveloped and have experienced vegetation re-establishment and / or minor weathering. Reconditioning of the lots on these parcels and recertification will therefore be necessary prior to planned on-site construction. Foundation Design Criteria Conventional Foundations The planned residential structures may be supported on conventional continuous and spread footings bearing on compacted engineered fill. For potential low soil expansion, continuous and spread footings may be designed based on the following criteria: Allowable Bearing Pressure (1) = 1,500 psf Minimum Footing Depth (2) = 18 inches Minimum Footing Width = Per 2010 CBC Passive Soil Pressure (3) = 250 psf/ft., subject to a maximum of 2,000 psf Friction Coefficient = 0.35 (ultimate) SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 3 of 21 Summerly Development City of Lake Elsinore, California Minimum Footing Reinforcement = For continuous footings, min. two No. 4 bars, one at top and one at bottom. Garage Door Grade Beam = 12 inches square with two No. 4 bars, one at top and one at bottom. The grade beam should be tied to the adjacent footings (1) The above value may be increased 250 lbs./sq.ft. for each additional foot exceeding the minimum embedment depth, subject to a maximum of 2,500 psf. Allowable bearing pressures may be increased by one-third for short term loading due to wind or seismic forces. (2) Footing depth is below lowest adjacent soil grade. (3) Passive soil pressure value is for level soil conditions adjacent to footings. Post-Tensioned Slab/Footings As an alternate to conventional foundations, post-tensioned slab foundation systems may be preferable to conventional foundations/slabs and offer the following advantages: • Post-tensioned slabs can provide additional foundation and slab rigidity and help in mitigating potential effects due to differential soil movement resulting from settlement and soil expansion. • Some residential developers have recently opted for post-tensioned slab/footing design on some sites without consideration of existing on-site soil conditions, stating that construction of post-tension slabs are less labor intensive. • Some developers prefer post-tensioned slabs due to the higher degree of quality control (e.g. concrete inspector required, etc.). Also, cracking development as a result of concrete shrinkage tends to stay closed longer. The Owner and Project Civil/Structural Engineer should evaluate the suitability of such a foundation system for the project site conditions and needs SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 4 of 21 Summerly Development City of Lake Elsinore, California Presented below are preliminary geotechnical criteria for post-tensioned slab/footings. These parameters are based on low soil expansion and the "Design of Post-Tensioned Slabs-On-Ground (Third Edition with 2008 Supplement) by the Post-Tensioning Slab Institute: Thornthwaite Moisture Index -20 Constant Suction (pF) 3.9 Center Lift Condition Edge Moisture Variation Distance, em 9.0 feet Differential Swell, ym 0.24 inches Edge Lift Condition Edge Moisture Variation Distance, em 5.3 feet Differential Swell, ym 0.61 inches Minimum Depth of Footings 12 inches (perimeter) Slab Thickness Per Structural Engineer Sub-grade Pre-saturation Presoak or maintain a soil moisture condition of approx. 1-3 percentage points above the optimum moisture content to a depth of 12 inches Note: The above design parameters are based on climatic conditions only, and are applicable for sites with proper site drainage, landscaping and irrigation, and adequately maintained as addressed hereinafter. Raised Floor Foundation Option Post-construction problems typically associated with soils and moisture/water vapor intrusion can be reduced by isolation of the living space floor areas from direct contact with the ground, with the exception of footings. A very effective technique used in the past and in other areas of the country is that of incorporation of raised floors. Most SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 5 of 21 Summerly Development City of Lake Elsinore, California commonly, these foundations are known as "raised-wood-floor" foundations that rely on perimeter stemwalls and interior strip and isolated footings that allow for a subfloor to be raised from contact with the ground. This produces a "crawl-space" between the soil surface and the base of the subfloor. The air-gap is typically 1 to 1.5-feet, and produces a very effective capillary break to stop water vapor intrusion from migrating into the living areas. The effects of poor drainage conditions are generally less damaging. The crawl space also makes plumbing and other utility installation and maintenance much easier to deal with than that presented by a slab-on-grade system. Because the foundations directly transfer loads from the raised floor, more uniform soil loading, and higher confining loads are also developed that help mitigate expansive soils effects. Preliminary recommendations for this option can be provided at a later date, upon request, if this option is desired. General Foundation Remarks a) Foundation details such as concrete strength, reinforcements, etc. should be established by the Project Structural Engineer, considering the low soil expansion potential and loading and service conditions. The reinforcements provided should be considered as minimum requirements. b) Isolated column footings should be tied together by grade beams in at least two (2) orthogonal directions. c) Foundation excavations should be observed and approved by the Project Geotechnical Engineer prior to the placement of reinforcement or concrete. Forming of footing excavations may be required. Excavations should be free of slough and debris and thoroughly moisture conditioned prior to placing concrete. d) Excavated materials from footings and utility trenches should not be placed in slab-on-grade areas unless properly compacted and tested under the observation and testing by the geotechnical engineer. SoitWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 6 of 21 Summerly Development City of Lake Elsinore, California e) Footing depths should not be allowed to be affected adversely, such as through erosion, softening, digging, landscaping, etc. f) Where foundations encroach closer than five (5) feet horizontally from the flow line of drainage swales, the footing should be deepened sufficiently to maintain the required embedment depth below the adjacent flow line. g) Exposed footing excavations and slab subgrade soils should be pre-soaked and/or maintained at a soil moisture condition of 1-3 percentage points wet of optimum moisture content to a depth of at least 12 inches. Structure Movement Some structure movement should be expected both during and following construction, even when supported on engineered compacted fill, due to various factors including, but not limited to: • Sequence of foundation and slab loading during construction; • Variation in structural loads along foundation elements; • Variation in underlying soil types with different compressibility indices and subsurface soil profile, and associated primary and long-term secondary consolidation settlements; • Moisture changes due to climatic and non-climatic influences following construction, and associated shrink/swell of expansive soils; It should also be recognized that given residential construction tolerances, concrete floor slabs will not be cast perfectly level, and it has been our experience that floors slab elevations across a residence may vary by as much as an inch or more. For design purposes and considering the above factors, static settlements for continuous and spread footings designed in accordance with the above recommendations and for structural loading typical for the residential-type construction SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 7 of 21 Summerly Development City of Lake Elsinore, California (column and wall loads not exceeding 30 kips and 3 kips/lineal foot, respectively) are not anticipated to exceed 1-inch total. In addition, differential movement between similarly loaded adjacent column footings and for continuous footings and slabs over a distance of 30 feet are not expected to exceed 3/4 inch. The potential differential movement for slabs specified above does not include potential deformations as a result of subgrade responses to seasonal and other moisture variation and expansive soils phenomena, which may exceed the above specified values. Seismic Design Considerations The site, as is all of southern California, is within a zone of seismic activity. Strong ground motion from an earthquake generated along active faults should therefore be anticipated at this site. The proposed development should be designed and constructed to the prevailing seismic design standards. Seismic design should be based on current and applicable CBC requirements, as appropriate. The 2010 CBC (2010 ASCE 7) Seismic Design Parameters are presented in Appendix A. Slab on Grade For design purposes, concrete floor slabs should be designed to resist potential expansive soil pressures and structural and/or construction loading considerations. The slab design and construction details should be established by the Project Design Engineer. From a geotechnical standpoint, the minimum criteria for slab-on grade are shown below: a) Concrete Floor Slabs for Conventional Foundation Construction Concrete floor slabs should be 4 inches thick (minimum) and should be reinforced with No. 4 bars at 18 inches on center, each way at mid height. No. 4 bars at 18 inches on center should be provided connecting floor slabs to footings. In order to minimize migration of moisture up the concrete slab from soil sub- SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 8 of 21 Summerly Development City of Lake Elsinore, California grade and damage to floor coverings, a moisture barrier/water vapor retarder system should be placed beneath floor slabs as recommended hereinafter. b) Garage Floor Slabs for Conventional Foundation Construction Garage floor slabs should be 4 inches thick (minimum) with No. 4 bars at 18 inches on center, each way at mid-height. The slabs should be quartered or saw- cut. The floor slab should be isolated from stem wall footings. Provide 4 inches pea gravel below slab. Generally, a moisture/water vapor retarder system is not considered necessary for the garage floor slab, provided that a moisture sensitive floor covering, built-in features, or other moisture sensitive objects will not be placed on the slab. A grade beam should be placed across the garage door opening as described in the Conventional Foundation Design Criteria section. c) Driveways Driveway concrete slabs should be 4 inches thick (minimum). No moisture barrier is required under driveway slabs. From a design standpoint, the project Civil / Structural Engineer may want to increase the slab thickness and / or incorporate reinforcing in the slab based on the planned construction joint spacing, design compressive strength of concrete, service load conditions, etc. d) Exterior Flatwork Sidewalks and walkways should be 4 inches thick (minimum). Hardscape areas within two feet of the descending slopes should include a thickened edge deepened to provide a minimum five (5) feet horizontal setback between the bottom outside face of the thickened edge and slope face. c) Slab Sub-grade Pre-saturation Prior to concrete placement, the prepared soil sub-grade should be moisture conditioned to and maintained at about 1 to 3 percentage points wet of optimum moisture contents to a depth of 12 inches and exhibit at least 90 percent relative compaction as determined by ASTM: D1557. SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 9 of 21 Summerly Development City of Lake Elsinore, California d) General Flatwork Remarks • Interior floor slabs and exterior concrete flatwork should be properly designed for the construction and service loading conditions, and potential differential movements. The structural details, such as slab thickness, concrete strength, reinforcing criteria, joint spacing, etc. should be established by the Project Civil / Structural Engineer. The recommended minimum reinforcements for concrete slabs provided above are intended for preliminary design only. More restrictive criteria as dictated by structural design or regulatory requirements shall govern. • All reinforcement must be appropriately spaced and supported/maintained during the pouring/finishing work such that it remains in proper condition. • Unless specifically allowed for and approved as such by the project Civil Engineer, no water is to be added to the concrete mix after the truck leaves the plant. It should be cautioned that addition of water to the concrete mix will change the water-cement ratio of the plant design mix and can lead to undesirable shrinkage cracking, curling, etc. of concrete slabs during curing. • All concrete to be properly finished per American Concrete Institution / Portland Cement association standards and moist cured (for preferably at least 7 days). If moist curing is not feasible, an appropriate curing compound / sealant should be applied in accordance with the timing and methodology specified by the curing compound manufacturer. • Truck tickets to include mix design, time leaving plant, time of site arrival, and time onsite / location of pour to be documented and copies sent to the project engineer. • All poured concrete should be protected from loading and traffic for at least 7- days without written approval of the project engineer. SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 10 of 21 Summerly Development City of Lake Elsinore, California Moisture/Water Vapor Retarder for Concrete Slab-on-Grade It should be recognized that, even with site surface and sub-drainage measures, there is potential for saturation of ground beneath concrete floor slabs due to water infiltration from irrigation, rain, and run-off or flow through the soil subgrade. The upward migration of moisture in vapor phase from soil subgrade through the slab-on-grade is inevitable under normal living conditions as they exist within a closed environment (e.g., residence). It is imperative that the Contractor properly install the recommended site drainage measures, utility trench backfill, and the moisture/water vapor retarder system in accordance with the project design requirements and specifications to mitigate potential moisture/water vapor transmission into the structures. In order to reduce the potential for moisture/water vapor migration up through the slab and possibly affecting floor covering, wood cabinets and other objects, a moisture/vapor retarder is recommended under concrete slab-on-grade. The recommendations provided below are based on the guidelines of the American Concrete Institute (ACI Committee Report 302.1 R-96): • The moisture/water vapor retarder should consist of high strength polyethylene membrane and should meet or exceed the ASTM: E-1745-97 Class C material requirements for water vapor permeance, tensile strength and puncture resistance. The vapor retarder should consist of "Moistop Plus" (Fortifiber Building Products Systems) or "Vapor Block" VB 15 (Americover, Inc.), or approved equal. The vapor retarder should be underlain by a capillary break comprised of minimum 4 inches thick pea gravel layer. The gravel layer should be placed and compacted on approved soil sub-grade. • The installation of the moisture/water vapor retarder system requires specialized knowledge and experience and should be accomplished with the technical assistance and supervision of retarder system manufacturer and/or supplier. The membrane should be placed on approved gravel layer and properly lapped and Soil Works Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 11 of 21 Summerly Development City of Lake Elsinore, California sealed. Membranes intersecting utility pipes, sewer lines, ducts or drains must be properly wrapped around the penetrations and sealed. All punctures and rips in the membrane should be repaired prior to placement of concrete, following manufacturer's recommendations. • The vapor retarder should be installed in general accordance with the procedures outlined in ASTM: E-1643, and in conformance with the installation procedures recommended by the manufacturer. • To minimize slab curling, a low shrinkage / low slump concrete (concrete mix with a 4,500 psi compressive strength and water cement ratio of 0.45) should be used for the slab construction, as determined by the Project Structural Engineer. The mix design should be verified by the project Civil / Structural Engineer, and placement of concrete should be observed and certified by the Concrete Deputy Inspector. • In addition, floor coverings (e.g., wood, tile, etc.) and other built-in features should be carefully selected with vapor transmission in mind, and include proper preparation and installation in accordance with the manufacturer's recommendations. • It should be emphasized that, even with proper moisture/water vapor installation, proper control of irrigation and landscape water adjacent to the structure is very important to minimize problems caused by moisture and water vapor intrusion, and is the responsibility of the Homeowner. In addition, the Homeowner and Homeowner's Association (H.O.A.) is responsible for maintaining proper site drainage as recommended hereinafter. Soil Expansion Based on laboratory test results presented in Reference Nos. 9 and 10, the fill soils underlying the subject tract consist predominantly of silty and clayey sands exhibiting Soil Works Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 12 of 21 Summerly Development City of Lake Elsinore, California very low to low soil expansion characteristics. Considerations for this potential soil expansion should be incorporated in the design and construction, as appropriate. Soil Corrosivity and Concrete The results of soluble soil sulfate tests presented in Reference Nos. 9 and 10 and Table 4.3.1 of ACI 318 Building Code (Table 4.2.1 of ACI-318-08), sulfate exposure to concrete is considered negligible (not applicable), and there are no special requirements for concrete in contact with soils. However, it has been our experience that post-construction factors such as the use of fertilizers in lawn/landscape areas, near surface soil wetting and drying cycles, etc. can increase the soluble sulfate contents and these conditions predispose them to being highly corrosive to both concrete and buried metals. Higher strength concrete with lower water/cement ratio will improve overall slab performance, durability, water and corrosivity resistance. As recommended in the "MoistureMater Vapor Retarder for Concrete Slab-on-Grade", a low shrinkage / low slump concrete (concrete mix with a 4,500 psi compressive strength and water cement ratio of 0.45) should be used for the slabs constructed on the moisture water vapor retarder system. Use of admixtures in the concrete mix can enhance the workability of the concrete, reducing bleeding, facilitate finishing, and reduce potential for slab cracking during curing. For this reason, it may be prudent to use a concrete mix designed specifically for concrete floor slab application. As a minimum, and subject to the approval of the project Civil / Structural Engineer, concrete with minimum 2,500 psi strength and maximum water:cement ratio of 0.5 may be used for exterior hardscape construction. Laboratory tests to evaluate the potential soil corrosivity to metallic installations were not performed. In the absence of such testing, the soils along with any transient waters flowing through them should be considered to be highly corrosive to metals in contact SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 13 of 21 Summerly Development City of Lake Elsinore, California with them. Attention to minimizing galvanic / chemical corrosivity (i.e., protective coatings, dielectric couplings, eliminating mixing metal types in contact or in near vicinity to each other) where in contact with soil and soil moisture can minimize these effects. An experienced corrosion consultant should be retained and their recommendations incorporated into the design if special / critical corrosive issues exist or further corrosion potential study is warranted. Retaining Walls Ancillary retaining walls may be designed based on the following criteria: • Retaining wall footings supported on approved engineered compacted fill may be designed based on a maximum allowable soil pressure of 1,500 psf. The recommended minimum footing depth is 2 feet below lowest adjacent soil grade. • Retaining wall footings should be adequately designed to resist the lateral soil pressures and the anticipated construction and service load conditions. The earth pressure acting on retaining walls depends primarily on the allowable wall movement, type of backfill materials, backfill slopes, wall inclination, surcharges, and any hydrostatic pressure. The following minimum lateral earth pressures are recommended for vertical cantilevered retaining walls with no hydrostatic pressure and no surcharge loading: Lateral Earth Pressure Wall Condition Backfill Slope (Equivalent Fluid Pressure) Active Case Level 40 pcf (Cantilever Walls) 21-1 : 1 V 65 pcf SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 14 of 21 Summerly Development City of Lake Elsinore, California The above values are applicable for walls backfilled with non-expansive, free- draining granular backfill (sands) placed between the wall and a 45 degree imaginary plane projecting upwards and outwards from the heel of the wall footing. • The surcharge effect of anticipated adjacent loads located on the wall backfill (e.g., traffic, footings) should be included in wall design. For cantilever walls, an additional lateral pressure equal to 33 percent of the maximum surcharge load located within a distance equal to the wall height should be used in design. • The wall design should include waterproofing (where appropriate) and weep holes or backdrains for relieving hydrostatic pressure. The backdrain should consist of perforated Schedule 40 PVC pipe, minimum 4-inch diameter, embedded in minimum 3 cubic feet / foot of gravel, and enveloped in Mirafi 140 geo-fabric or approved equal. The drain pipe should be installed as a minimum gradient of 1 percent and should discharge unto a suitable outlet. • No backfill should be placed against concrete until minimum design strengths are attained, as determined by concrete compression tests. • Retaining wall backfill should be mechanically compacted to 90 percent (minimum) relative compaction (ASTM: D1557). No ponding, jetting or flooding should be permitted. Foundation Setbacks Structure and retaining wall foundations located adjacent to slopes should be setback laterally from the slope face in accordance with the 2010 CBC and the requirements of the City of Lake Elsinore. The horizontal setback distance from the outside edge of footings to the face of slope, as a minimum, should be no less than 10 feet. For minor masonry screen walls, a minimum horizontal setback of 5 feet from the outer edge of footings to the slope face may be considered. Soi/Works Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 15 of 21 Summerly Development City of Lake Elsinore, California Utility Trench Backfill a) The on-site soils consist mostly of clayey and silty sandy soils and are generally considered unsuitable for use as bedding material. Bedding and shading material should consist of sandy material exhibiting a Sand Equivalent (S.E.) value of 30 or greater, be free of objectionable inclusions and fines to prohibit free flow and hydro-consolidation, and should comply with the requirements of the controlling governing jurisdiction. Adherence to these requirements is important in order to prevent bridging of soils along the sides of the utility lines, infill potential voids around the base of pipe, and provide more uniform relative compaction of materials surround the line. b) The site soils are considered suitable for trench backfill, provided they are properly processed / moisture conditioned and free of organic material and rocks over 4 inches in maximum dimension. c) To reduce potential water migration into building sub-grade through the granular bedding/shading layer and trench backfill, utility trenches crossing beneath building perimeter edges should be backfilled with the onsite finer grained materials or sand-cement slurry for minimum 3 feet length at their entry points. Utility line backfill placed below or within a zone defined by a theoretical plane downwards and outwards at a 1:1 (horizontal to vertical) projection from the outside edge of footings should be compacted to a minimum 95 percent relative compaction or slurry backfilled (minimum 2 sack cement- sand mix). d) Backfill of all exterior and interior trenches should be placed in thin lifts not exceeding 4 inches and mechanically compacted to achieve a relative SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 16 of 21 Summerly Development City of Lake Elsinore, California compaction of not less than 90% based on ASTM: D1557. Care should be taken not to damage utility lines. e) Trenches greater than 4 feet in depth should be shored or sloped back as required by the local regulatory agency, the State of California Division of Industrial Safety Construction Safety Orders, and Federal OSHA requirements. The soil and temporary excavation conditions should be evaluated on a case-by-case basis by the project geotechnical engineer / engineering geologist, using the actual conditions exposed for developing recommendations regarding such excavations. Site Drainage Of all the post-construction maintenance items — attention to site drainage is the most important as water is the cause of most problems. The Homeowners, Landscape Architect, and H.O.A should be aware of the potential problems that may develop when drainage is altered through construction of retaining walls, paved walkways, and patios. Conditions which will lead to ground saturation must be avoided. a) All roof and surface drainage should be directed away from structures and their appurtenances and slopes to approved drainage facilities. Ponding of water should be avoided. Per the 2010 CBC, a minimum gradient of 5 percent away from structures should be maintained for graded soil areas to a distance of 10 feet or to approved drainage swales. b) The recommended drainage patterns should be established at the time of fine grading and maintained throughout the life of the structure or, if altered, should be replaced with properly designed area drain system. c) Irrigation activities at the site should be monitored and controlled to prevent over watering. Planter and lawn areas adjacent to structures should be avoided. If utilized, these should include measures to contain irrigation water Soi/Works Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 17 of 21 Summerly Development City of Lake Elsinore, California and prevent moisture migration into the walls and under foundations and slabs-on-grade. d) The selection of plant palettes should be based on that which is suitable for the area and be drought tolerant. e) It is imperative that all new construction maintain positive drainage to suitable discharge facilities. Adequate area drainage systems should be installed in planter areas and within flatwork areas, as required. Landscape, Irrigation, and Maintenance General guidelines for landscape, irrigation and maintenance are shown below: (1) Landscape planting should consist of appropriate drought resistant vegetation as recommended by the Landscape Architect. Landscaping of slopes should be completed as soon as possible and properly maintained. (2) The property owner is responsible for proper irrigation and for maintenance and repair of installed irrigation systems. Leaks should be repaired immediately. Sprinklers should be adjusted to provide maximum coverage with a minimum of water usage and overlap. Over-watering with consequent excessive runoff and ground saturation must be avoided. (3) If automatic sprinkler systems are installed, their use should be adjusted to account for natural rainfall conditions. (4) All interceptor ditches, drainage terraces, down-drains, and any other drainage devices that have been installed must be maintained and cleaned. (5) If rodent activity is present, the property owner should undertake a program for the elimination of burrowing animals. This should be an ongoing program in order to promote slope stability. SoitWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 18 of 21 Summerly Development City of Lake Elsinore, California (6) Water should be directed away from constructed or natural slopes faces. This may require the construction of berms or ditches along the top of slopes, if such devices are not in place. Plan Review, Observations and Testing During the design and precise grading phases, the final Precise Grading and Foundation Plans, including the design details of planned structures (e.g., location, configuration, design loads, etc.) should be provided to the Project Geotechnical Engineer to verify the applicability of the recommendations provided above and to develop additional and/or revised recommendations, as appropriate. Precise grading, including foundation and on-site construction should be performed under the observation, documentation, and testing by the Project Geologist and Geotechnical Engineer. To document actual conditions encountered, work performed, and any in-field modifications / adjustments, an As-Graded report should be prepared upon the completion of work. Closure Our review and preparation of this report are based on our experience, available documents and our knowledge of the site, and were obtained in accordance with currently accepted professional engineering principles and practice in the field of geologic and geotechnical engineering, and reflect our best professional judgment. We make no other warranty, either express or implied. This report is subject to supplementation and revision as new information becomes available and the designs are refined. This report is also subject to the review of the City of Lake Elsinore and any comments /responses become a part hereto and the project specifications. The recommendations provided by this firm are made on the assumption that we will be retained to perform the geotechnical onsite observation, testing and support associated with the proposed work. If another geotechnical firm is used, these and any other SoilWorks Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 19 of 21 Summerly Development City of Lake Elsinore, California applicable recommendations developed by this firm are considered void. SoilWorks is not responsible for any implementation of recommendations or grading / construction that it did not have an adequate opportunity to observe, test, comment on, and document. Similarly, should unanticipated conditions be encountered or alterations to the current design be made, this office should be given the opportunity and retainage to evaluate and provide revisions / updates as warranted. We appreciate the opportunity of being of service to you on this project. Should you have any questions or need additional information, please contact the undersigned. Sincerely, SoilWorks, Inc. �aCL Qcorrssio.;:�.. LQ By: _ No.GE2726 By: ((( \\ Daniel . Morik ., .E. >� Steven E. Strickler, P.E., G.E. RGE 27 6, Reg RGE 2265, Reg. expires 3/31/14 FOF CA0�� Attachments: List of Selected References Composite Tract Map 2010 CBC Seismic Design Criteria Distribution: Addressee (3) Soi/Works Earth Sciences Group McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 20 of 21 Summerly Development City of Lake Elsinore, California LIST OF SELECTED REFERENCES 1. Neblett & Associates Inc., Preliminary Geotechnical Investigation and 40-scale Grading Plan Review, Tentative Tract 31920, Phase I Residential and Golf Course Development, City of Lake Elsinore, County of Riverside California, dated December 15, 2004 (Project No. 420-000-05). 2. Neblett & Associates Inc., Additional Fault Investigation and Response to County of Riverside Report Review, Tentative Tract 31920, Summerly Site, City of Lake Elsinore, California, dated October 18, 2005 (Project No. 420-000-03) 3. Preliminary Geotechnical Investigation and 40-Scale Grading Plan Review, Tentative Tract 31920, Stage 2 of Summerly Development, City of Lake Elsinore, County of Riverside, California, dated February 7, 2006, Project No. 420-001-05. 4. Neblett & Associates Inc., Interim Rough Grade Compaction Report, Parcel 3, Stage 1, Summerly Development Site, Tract 31920, Lake Elsinore, California, dated September 27, 2006 (Project No. 420-000-07). 5. Neblett & Associates Inc., Interim Rough Grade Compaction Report, Parcel 5, Stage 1, Summerly Development Site, Tract 31920, Lake Elsinore, California, dated November 8, 2006 (Project No. 420-000-07). 6. Neblett & Associates, Inc., Interim Rough Grade Compaction Report, Parcel 2, Stage 1, Summerly Development Site, Tract 31920, Lake Elsinore, California, dated December 15, 2006 (Project No. 420-000-07). 7. Neblett & Associates, Inc., Interim Rough Grade Compaction Report, Parcel 8, Stage 1, Summerly Development Site, Tract 31920, Lake Elsinore, California, dated January 17, 2007 (Project No. 420-000-07). 8. Neblett & Associates, Inc., Interim Rough Grade Compaction Report, Parcel 7, Stage 1, Summerly Development Site, Tract 31920, Lake Elsinore, California, dated March 21, 2007 (Project No. 420-000-07). 9. Neblett & Associates, Inc., Final Rough Grade Compaction Report, Stage 1 of the Summerly Development Project, Tract 31920, Lake Elsinore, California, dated May 24, 2007, Project No. 420-000-07. 10. Neblett & Associates, Inc., Rough Grade Compaction Report, Stage 2 of the Summerly Development Project, Tract 31920, Lake Elsinore, California, dated November 30, 2007, Project No. 420-001-07. 11. SoilWorks, Inc., Foundation Design Considerations, Summerly Stage 1, Tract 31920, Lake Elsinore, California, dated May 24, 2011, Project No. 118-001-01. 12.Summerly - McMillin DDA, Tract Map Composite Exhibit, Sheet 1 of 1, Project No. 10001.13, undated. Soi/Works Earth Sciences Group �J R So- 1 4)O0 QO 000 ®® *0 000 0. Y 4 --` ol 3 C� CD I>j 3 •` k �n 0 u. i� U McMillin Land Development October 5, 2012 Geotechnical Report Update Project No. 118-003-01 Parcels 2, 3, 5, 7, 8, and 12, Tract 31920 Page 21 of 21 Summerly Development City of Lake Elsinore, California 2010 CBC SEISMIC DESIGN CRITERIA SoilWorks Earth Sciences Group Design Maps Summary Report http://geohazards.usgs.gov/designmaps/us/summary.php?template=mini... USGS Design Maps Summary Report User-Specified Input Building Code Reference Document ASCE 7-10 Standard (which makes use of 2008 USGS hazard data) Site Coordinates 33.648450N, 117.30149°W Site Soil Classification Site Class D -"Stiff Soil" Risk Category I/II/III lJfb Sun City a Simpson Rd 4VO Canyon �anycnlPkw Lake Menifee Lake I;`r:r.r,re Lake fnR0 State Elsinore X jt-AroadV 5d Re,(eatign Airs g, (741 Lakeland Sedco Hilfs Scott Rd village o Wildomar ¢ unfree t3tates r Mexlco USGS-Provided Output SS = 2.513 g SMs = 2.513 g SpS = 1.675 g Sl = 1.021 g SMl = 1.532 g SDI = 1.021 g For information on how the SS and S1 values above have been calculated from probabilistic (risk-targeted) and deterministic ground motions in the direction of maximum horizontal response, please return to the application and select the"2009 NEHRP"building code reference document. MCER Response Spectrum Design Response Spectrum 2.96 1.27 2.60 1.70 2.34 1.53 2.09 1.36 1.92 1.19 co 1.56 1.02 •r tir 1.30 H 0.95 1.04 0.68 0.79F 0.51 0.52 0.34 0.26 0.17 0.00 0.00 0.00 0.20 0.40 0.60 0.90 1.00 1.20 1.40 1.60 1.90 2.00 0.00 0.20 0.40 0.60 0.90 1.00 1.20 1.40 1.60 1.90 2.00 Period.T(sec) Period.T(sec) For PGAM,TL, CRS, and CR, values, please view the detailed report. Although this information is a product of the U.S. Geological Survey,we provide no warranty,expressed or implied,as to the accuracy of the data contained therein.This tool is not a substitute for technical subject-matter knowledge. 1 of 1 10/3/2012 5:27 PM Design Maps Detailed Report http://geohazards.usgs.gov/designmaps/us/report.php?template=minimal... MUM Design Maps Detailed Report ASCE 7-10 Standard (33.648450N, 117.30149°W) Section 11.4.1 — Mapped Acceleration Parameters Note: Ground motion values provided below are for the direction of maximum horizontal spectral response acceleration. They have been converted from corresponding geometric mean ground motions computed by the USGS by applying factors of 1.1 (to obtain SS) and 1.3 (to obtain S1). Maps in the 2010 ASCE-7 Standard are provided for Site Class B. Adjustments for other Site Classes are made, as needed, in Section 11.4.3. From Figure 22-1 �lI Ss = 2.513 g From Figure 22-2 E21 S1 = 1.021 g Section 11.4.2 — Site Class The authority having jurisdiction (not the USGS), site-specific geotechnical data, and/or the default has classified the site as Site Class D, based on the site soil properties in accordance with Chapter 20. Table 20.3-1 Site Classification Site Class v N or N s s cn U A. Hard Rock >5,000 ft/s N/A N/A B. Rock 2,500 to 5,000 ft/s N/A N/A C. Very dense soil and soft rock 1,200 to 2,500 ft/s >50 >2,000 psf D. Stiff Soil 600 to 1,200 ft/s 15 to 50 1,000 to 2,000 psf E. Soft clay soil <600 ft/s <15 <1,000 psf Any profile with more than 10 ft of soil having the characteristics: • Plasticity index PI > 20, • Moisture content w >_ 40%, and • Undrained shear strength s < 500 psf u F. Soils requiring site response See Section 20.3.1 analysis in accordance with Section 21.1 For SI: 1ft/s = 0.3048 m/s ilb/ft2 = 0.0479 kN/mz 1 of 6 10/3/2012 5:28 PM Designs Maps Detailed Report http://geohazards.usgs.gov/designmaps/us/report.php?template=minimal... Section 11.4.3 - Site Coefficients and Risk-Targeted Maximum Considered Earthquake (MCE ) .....................R Spectral Response Acceleration Parameters Table 11.4-1: Site Coefficient F a Site Class Mapped MCE R Spectral Response Acceleration Parameter at Short Period Ss :50.25 Ss = 0.5 Ss = 0.75 Ss = 1 Ss >_ 1.25 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 D 1.6 1.4 1.2 1.1 1.0 E 2.5 1.7 1.2 0.9 0.9 F See Section 11.4.7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of S s For Site Class = D and SS = 2.513 g, Fa = 1.000 Table 11.4-2: Site Coefficient F Site Class Mapped MCE R Spectral Response Acceleration Parameter at 1-s Period S <_ 0.1 S = 0.2 S = 0.3 S = 0.4 S >_ 0.5 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.7 1.6 1.5 1.4 1.3 D 2.4 2.0 1.8 1.6 1.5 E 3.5 3.2 2.8 2.4 2.4 F See Section 11.4.7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of S For Site Class = D and Sl = 1.021 g, F� = 1.500 2 of 6 10/3/2012 5:28 PM Desigri'Maps'Detailed Report http://geohazards.usgs.gov/designmaps/us/report.php?template=minimal... Equation (11.4-1): SMs = F a S S = 1.000 x 2.513 = 2.513 g Equation (11.4-2): S M1 v 1= F S = 1.500 x 1.021 = 1.532 g Section 11.4.4 — Design Spectral Acceleration Parameters Equation (11.4-3): SDS = % SMs = % x 2.513 = 1.675 g Equation (11.4-4): SDI = i/3 SMl = 2/ x 1.532 = 1.021 g Section 11.4.5 — Design Response Spectrum From Figure 22-12[31 T = 8 seconds Figure 11.4-1: Design Response Spectrum T<T.:S.=S,,(0.4+b.6T1T,o) Sc,;=1675 -- 1 Tr5T5Ta:5a=So, � 1 T$<TST,:S.=Sot1T M I t I ( a i i T>T�:S.=%ITLIT" � I 1 ` 1 ( a ' ' � 1 I u — - I --------- � 1 I 1 � I 1 C I 1 1 0 1 1 1 U, I 1 1 I 1 , ID 1 1 1 IJ I 1 i d 1 1 a 1 , I , 1 T,=0.122 T;=0.610 1.000 Period,T(sec) 3 of 6 10/3/2012 5:28 PM DesjgwiWapS Detailed Report http://geohazards.usgs.gov/designmaps/us/report.php?template=minimal... Section 11.4.6 — Risk-Targeted Maximum Considered Earthquake (MCER) Response Spectrum The MCER Response Spectrum is determined by multiplying the design response spectrum above by 1.5. =251"a -- 1 of , 1 � I , I I I � u SMI=1.532 - -------------I--------- I I I I a I I I "c a I I I a N 1 I I C, I I I 6. I I 1 I I 1 4 rn I I I I I I I 1 I I I I I I I I I Ta=0.122 T,=0.610 1.000 Period.T(sec) 4 of 6 10/3/2012 5:28 PM Des'gd Maps'Detailed Report http://geohazards.usgs.gov/designmaps/us/report.php?template=minimal... Section 11.8.3 - Additional Geotechnical Investigation Report Requirements for Seismic Design Categories D through F From Figure 22-7[41 PGA = 0.969 Equation (11.8-1): PGAM = F PGA PGA = 1.000 x 0.969 = 0.969 g Table 11.8-1: Site Coefficient F PGA Site Class Mapped MCE Geometric Mean Peak Ground Acceleration, PGA PGA 5 0.1 PGA = 0.2 PGA = 0.3 PGA = 0.4 PGA >: 0.5 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 D 1.6 1.4 1.2 1.1 1.0 E 2.5 1.7 1.2 0.9 0.9 F See Section 11.4.7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of PGA For Site Class = D and PGA = 0.969 g, FPGA = 1.000 Section 21.2.1.1 - Method 1 (from Chapter 21 - Site-Specific Ground Motion Procedures for Seismic Design) From Fiaure 22-17 C = 0.899 PIS From Figure 22-18[61 C = 0.884 R1 5 of 6 10/3/2012 5:28 PM Design Maps Detailed Report http://geohazards.usgs.gov/designmaps/us/report.php?template=minimal... Section 11.6 — Seismic Design Category Table 11.6-1 Seismic Design Category Based on Short Period Response Acceleration Parameter VALUE OF S RISK CATEGORY os I or II III IV Sps < 0.167g A A A 0.167g 5 Sps < 0.33g B B C 0.33g 5 Sos < 0.50g C C D 0.50g 5 Sos D D D For Risk Category = I and Sos = 1.675 g, Seismic Design Category = D Table 11.6-2 Seismic Design Category Based on 1-S Period Response Acceleration Parameter RISK CATEGORY VALUE OF Sol I or II III IV SDI < 0.067g A A A 0.067g 5 SDI < 0.133g B B C 0.133g 5 SDI < 0.20g C C D 0.20g 5 SDI D D D For Risk Category = I and Spl = 1.021 g, Seismic Design Category = D Note: When S1 is greater than or equal to 0.75g, the Seismic Design Category is E for buildings in Risk Categories I, II, and III, and F for those in Risk Category IV, irrespective of the above. Seismic Design Category - "the more severe design category in accordance with Table 11.6-1 or 11.6-2" = E Note: See Section 11.6 for alternative approaches to calculating Seismic Design Category. References 1. Figure 22-1: http://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7_Figure_22-1.pdf 2. Figure 22-2: http://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7_Figure_22-2.pdf 3. Figure 22-12: http://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE- 7_Figure_22-12.pdf 4. Figure 22-7: http://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7_Figure_22-7.pdf 5. Figure 22-17: http://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE- 7_Figure_22-17.pdf 6. Figure 22-18: http://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE- 7_Figure_22-18.pdf 6 of 6 10/3/2012 5:28 PM