HomeMy WebLinkAboutPUD 16-08; COVE DR CONDOS; PRELIMINARY DRAINAGE STUDY; 2006-09-11------------PRELIMINARY DRAINAGE STUDY
COVE DRIVE -.. -----..
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• Kim L. Post, R.C.E. 23166
• Vista Engineering, Inc.
930 Vista Village Drive
• Vista, California 92084-6064
• (760) 941-2271 -Office
(760) 941-7928 -Fax ----
September 11, 2006
PREPARED FOR:
Jerzy & Jolanta Lewak
4954 Sun Valley Road
Del Mar, CA 92014
Job No. 141-04
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• PRELIMINARY DRAINAGE STUDY
LOT 31, COVE DRIVE, CARLSBAD -----------------------------• ----
SITE DESCRIPTION & CONCLUSIONS:
The subject property is a nearly level dirt lot with virtually no vegetation. The northeasterly
end of the property slopes down to the waterline of the Agua Hedionda Lagoon at an
approximately 2:1 slope which is armored with riprap. There are no existing structures on
the property.
The project vicinity is characterized by multi-family residences or vacation residences on
narrow lots extending between Cove Drive and the lagoon. There is no drainage basin
tributary to the site since Cove Drive drains southeasterly and not onto the site.
Additionally the properties on either side of the site can drain to the lagoon directly,
although currently minor runoff from the property to the south may enter the site.
Minor increases in runoff quantities due to proposed impervious surfaces are not a concern
since the site drains directly to the Agua Hedionda Lagoon which is connected to the
Pacific Ocean. Water quality protections are proposed within the storm drain system.
RUNOFF:
Using the Rational Method from the County of San Diego Hydrology Manual, June 2003,
the 0 100 rainfall runoff from the site is calculated using the equation:
With i100 = 6.9 iph from the Intensity-Duration Design Chart (County Figure 3-1) and the 100
year 6 hour and 24 hour Rainfall lsopluvial maps, and the runoff coefficient C = 0.71 (for
HOR, 24 DU/A or less in County Table 3-1) for Soil Type 'D':
Runoff from the Northwest ½ Site:
Runoff from the Southeast ½ Site:
HYDRAULICS:
0 100 = Ci100 A= (0.71)(6.9)(0.05) = 0.25 cfs
0 100 = Ci100 A= (0.71)(6.9)(0.05) = 0.25 cfs
The proposed storm drain piping system consists of a 6" PVC main line on each side of
the property that small yard drains and roof drains will connect to which conveys runoff
through a filtration box and into the lagoon (see grading plan). The 6" PVC has been
designed with a minimum slope of 0.50%. Per the following worksheet, 6" PVC at this
slope is able to convey 0.40 cfs which exceeds the runoff from either half of the site
calculated above. The filter in the filtration box is able to treat 0.90 cfs per the
manufacturers specifications which also exceeds the calculated flow.
VISTA ENGINEERING, INC. I R.B. HILL & ASSOCIATES, INC. 930 Vista Village Drive, Vista, California 92084
CIVILENGINEERINGANDLANDSURVEY/NG (760) 941-2271 • Fax (760) 941-7928