HomeMy WebLinkAboutTR 35337 HYDROLOGY REPORT-028 Spyglass Ranch Tract 35337
Hydrology Study
area. Tables 2 and 3 provide a complete summary of the rational method
analysis for each drainage area.
Table 16 provides a summary of Basin #1 Volume vs. Depth relationship,
as related to the required water quality treatment.
Table 16: Basin #1 — Volume Vs. Depth for Water Quality
Contour Contour Volume Total Total Volume Basin
Elevation Area (CF) Volume (Acre—FT) Depth
(SF) (CF) (FT)
1400.00 36800 36200 176600 4.0542 4.50
1399.50 35600 34950 140400 3.2231 4.00
1399.00 34300 33100 105450 2.4208 3.50
1398.00 31900 30700 72350 1.6609 2.50
1397.00 29500 28350 41650 0.9562 1.50
1396.00 27200 13300 13300 0.3053 0.50
1395.50 26000 0 0 0.0000 0.00
Vbmp = 71400 1.6391
Vbmp Water Depth = 2.5
Areas ,F,, and "G"
Areas 'IF" and "G" are drainage areas in the post—developed condition
that are primarily comprised of park site and commercial land use. The
comparable drainage area in the pre—developed, or existing condition is
Area 13. The low flows that require water quality treatment for this area
originate from the park site and commercial site building pad. Since the
site plans for these parcels are not available at this time, the impervious
fraction cannot be calculated accurately. Accordingly, the applicable BMP
devices will be designed and installed in accordance with NPDES guidelines
at the time the site plans are proposed for these developments. These
water quality treatment facilities are anticipated to be located within the
park site and within the commercial development.
The higher storm flows are designed to discharge into the existing 36"
and 18" culverts located in Camino Del Norte. The rational analysis
indicates that the combined developed condition peak flow rates of Areas
'IF" and "G" are less than the total pre—developed condition peak flow rate
of Area 13. It follows, consequently, that the capacity of the existing
culvert will not be exceeded and therefore no storm mitigation is required
for this area. Tables 2 and 3 provide a complete summary of the rational
method analysis for each drainage area.
Area "H"
Area "H" is a drainage area in the post—developed condition that is
primarily comprised of natural area. The comparable drainage area in the
pre—developed, or existing condition is Area 14. Since the vast majority of
H: \265324\Final,\llydrology\Rcporl\:32a Report Body.dog x — 24 —