HomeMy WebLinkAboutCDP 01-41; Garfield Street Homes; Hydrology and Hydraulic Report; 2002-06-14Sea Briohi
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June 14, 2002
GARFIELD HOMES
CDP 01 -41
HYDROLOGY & HYDRAULIC REPORT
The above subject lot is a small vacant infill lot about .14 acres in size. It
presently drains away from Garfield Street in a gentle northeasterly direction to
the rear of the lot. The rear of the lot "drains over" an existing 3' retaining wall
onto the A.C. parking lot of an existing multifamily development.
The proposed development wili drain in the same direction as it does now.
In order to "purify" and minimize additional runoff from what presently exists, an
extensive gravel drain has been introduced along the northeastern comer of the
property. This will "cleanse" the runoff, reduce the velocity, and provide a
mechanism for ground soaking/recharge. Typical nuisance water or light rain
runoff should never leave the property.
The southeastern side of the project does not have the same gravel drain
proposed. This was done because of the basement condition at the southeast
comer of the building. I did not want to promote ground recharge in this area.
Fortunately this side of the project will receive a minor increase in runoff from
roof areas only. To mitigate this I have 18" deep gravel dry wells at down spout
locations. This will take care of very small flows. If heavier rains occur, I have
provided for a 6' x 3' x 2' deep "absorption pit" in the,middle back of the property.
This would be the last point of water filtration and absorption before additional
waters might possibly flow over the existing wall, as it presently is allowed to do.
A concrete curb with a 4" outlet pipe has also been introduced to control
additional flows as well as promote ground recharge due to it's possible
reducing capabilities. See the attached calculations regarding flows and pi^pe
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Engineering Management General Contracting Development
4322 Sea Bright Place Carlsbad, CA 92008 Telephone/FAX 760-720-0098
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DEPARTMENT OF SANITATION g.
FLOOD CONTROL 100-YEAR 6-HOUR PRECIPITATiOfJ
'20-/ ISOPLUVIALS OF lOO-YEAR 6-HOUR
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33'
Prepn i;
U.S. DEPARTMEN
SPECIAL STUDIES BRANCH, OFFICE OF II
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NATIONAL OCEANIC AND AT.NjoSPMEHIC ADMINISTRATION
DROUOCY. NATIONAL WEATIIER SERVICE
APPFNOTY YT-H
COUNTY OF SAN DIEGO
DEPARTMENT OF SANITATION S
FLOOD CONTROL
33"
30'
15'
lOO-YEAR 24-IIOljR PRECIPITATION
^20-^ISOPLUVIALS OF 100 -YEAR 24-llOUR
PRECIPITATIOM IM EMTUS OF AM IMCH
Prepo
U.S. DEPARTMEN
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
SPECIAL STUDIES BRANCH. OFFICE OF 11
30'
16'
APPRNDIX XI-H
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SAN DIEGO COUNTY
DEPARTMENT OF SPECIAL DISTRICT SERVICES
APPROVED
DESIGN MANUAL
NOMOGRAPH FOR DETERMINATION
OF TIME OF CONCENTRATION (Tc)
FOR NATURAL WATERSHEDS
DATE APPENDIX X-A
lV-A-10 Rev. 5/81
INTENSITY-DUFATiv.. DESIGN CHART
rrrrlTrrnrr.
\ Equation: I 7.44 P. D o
-.645
Intensity (In./Hr.)
6 Hr, Precipitation (In.)
Duration (Min.)
I zc o c
1
•o
T fD O
o
3
3
O
fD t/l
15 20 30
Minutes
Directions for Application:
1) From precipitation naps determine 6 hr. and
24 hr. amounts for the selected frequency.
These maps are printed in the County Hydro!on>
Manual (10, 50 and 100 yr. maps included in tl
Design and Procedure Manual).
2) Adjust 6 hr. precipitation (if necessary) so
that it is within the range of 45% to 65% of
the 24 hr. precipitation. (Not applicable
to Desert)
3) Plot 6 hr. precipitation on the right side
of the chart.
4) Draw a line through the point parallel to the
plotted lines.
5) This line is the intensity-duration curve for
the location being analyzed.
Application Form:
0) Selected Frequency \00 yr.
1) = 2>5 in.. p.^= 4.0 . \ =
2) Adjusted *Pg= Z.'v
24
in.
3) \-0 min.
4) I = ^-Z. in/hr.
*Not Applicable to Desert Region
Revised ^vDvvnry YT-/<