HomeMy WebLinkAboutCDP 02-35; HENDRIX SECOND DWELLING UNIT; HYDROLOGY STUDY AND DRAINAGE CALCULATIONS; 2003-03-06• ENGINEERING
Peter S. Geissler
Civil Engineer Lie. C44320
Contractor Lie. A464570
f'lastino Building, Suite 230
2533 South Coast Highway 101
Cardiff-by-the-Sea, CA 92007
Office 760 -633 -4252
Fax 760 -633 -4259
Mobile 760 -815 -5054
HYDROLOGY STUDY & DRAINAGE CALCULATIONS
Date: 6 March 2003
Submitted to
Department of Engineering
City of Carlsbad, California
For and on behalf of
Edward A. Hendrix
470 Chinquapin Avenue
Carlsbad, CA
Project: Proposed Grate for Catch Basin
470 Chinquapin Avenue
Carlsbad, CA
Ref:
Client:
Geissler Engineering Project No. 03-454-1
Edward A. Hendrix
470 Chinquapin Avenue
Carlsbad, CA
HYDROLOGIC CALCULATIONS
Peak Runoff (50-year storm) = 4.0 inches per hour
Runoff Coeffic)(mt, C = 0.55 (vegetative hillside)
Tributary Drainage Area:
Area of Tributary Drainage Area (existing uphill residential hillside= 72,900 sq~
Page 1 of 2
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[Ref: City of Carlsbad Orthophoto Ma ping dated September-
October 1988, Copyright 1991]
[Note: No change in tributary drainage area is proposed. No additional pavement is proposed.
This study is an evaluation of the adequacy of the existing catch basin to control surface runoff
at the proposed development site.]
Peak Flow Requirement= (4.0) (0.55) (72,900) I ((12) (60) (60)) = 3.7 cu ft per second
The required .Q/A, discharge rate/ grate area, may be evalu_ated from the empirical equation, as
follows.
QI A= {5.37) -JH = {5.37) .J(o.5) = 3.8
Where
H = Depth (maximum) of at intake grating= 6 in= 0.5 ft
A= Required (net) Area at of at intake grating
Q = Peak flow (50-year storm)= 3.7 cu ft/sec
Calculation of Grate Size
Required Clear Area= (3.7) I (3.8) = 0.21 sq ft
Required Gross Area= (0.21) I (0.5) = 0.42 sq ft
Proposed Intake Grate= (1'-5") (111-611 = (1.42) (1.5) = 2.13 sq ft
Minimum cross-sectional area of intake grating = 0.42sq ft
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1.09 < 14 O.K.
0.42 < 2.13 0.K.