HomeMy WebLinkAboutMS 14-11; MATHIS LEVANTE SUBDIVISION; HYDROLOGY STUDY; 2020-07-25LA COSTA
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CIVIL • STRUCTURAL
MECHANICAL. PETROLEUM
TRECORD COPY
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Initial Date
1/7
HYDROLOGY STUDY
3144 LEVANTE DR.
CARLSBAD, CA 92009
APN 223-170-65-00
MS 14-11/GR2019-0034IDWG 498-1B
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LAND DEVt.Lur:NT
ENGINE .
PROJECT: PROPOSED SINGLE FAMILY DWELLING,
GRADING PLAN
ENGINEER: MARTELL B. MONTGOMERY
R.C.E. 50344 EXP. 6-30-21
DATE: AUGUST 5, 2019
REV. DATE: JULY 25, 2020
9,OFESsì
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No. C-50344f
Exp. 6-30-21
HYDROLOGY CALCULATIONS
100 YR, 6 HR STORM
Existing Condition (Proposed Development Area):
Pervious areas: 19,101 sf= 0.439 ac.
Impervious areas: 300 sf= 0.007 ac.
Runoff Coefficient 'C': Hydrology Group Type: D (See attached Soil Group Map)
Single Family(LDR)- Pervious: 0.41
Single Family(LDR)- Impervious: 0.90
Rainfall Intensity 'I': 6.59 in/hr (See Fig. 3-2 and 1 ooyr, 6hr/24hr precipitatioi charts)
For small watersheds, Tc = (Ti + TO, where (Ti + TIE) <= 5 mm. USE 5 mm.
Watersheds less than 0.5 sq.mi.:
Rational Formula: Q(cfs) = CIA
EXISTING DRAINAGE CONDITION (Total Site):
QE = [(0.41)(6.59 in./hr)(0;439 ac.)]+ [(0.90)(6.59 in./hr)(0.007 ac.)]= 1.23 cfs
Proposed Condition (Proposed Development Area):
Pervious areas: 11,599 sf= 0.266 ac.
Impervious areas: 7,502 sf= 0.172 ac.
Coefficient 'C': Hydrology Group Type: D
Single Family-Pervious: 0.41
Single Family-Impervious: 0.90
Rainfall Intensity 'I': 6.59 in/hr (See Fig. 3-2 and 100yr, 6hr/24hr precipitation charts)
For small watersheds, Tc = (Ti + TO, where (Ti + TIE) <=5 mm. USE 5 mm.
Watersheds less than 0.5 sq.mi.:
Rational Formula: Q(cfs) = CIA
z
PROPOSED FLOW CONDITION:
Qp = [(0.41)(6.59 in.Ihr)(0.266 ac.)]+ [(0.90)(6.59 in./hr)(0.172 ac.)]= 1.74 cfs
(PEAK FLOW)
CHANGE IN ON-SITE DRAINAGE FLOWS:
-Q =-(-, .74 cfs - 1.23 cfs) = 0.51 cfs Net Flow Increase.
DISCHARGE DESIGN:
Additional 0.51 cfs generated from 0.439 acre development area will be directed via
sheet flow to the 1307 sf gravel drive area and the 3385 s.f pervious payers proposed
throughout the driveway area. This is sufficient to accept this small, additional flow.
ANY MINIMAL DRAINAGE THAT DOES NOT INFILTRATE WILL
DISCHARGE TO LEVANTE STREET AT < 0.51 CFS. CAPACITY OF PUBLIC
DRAINAGE SYSTEM WILL NOT BE COMPROMISED.
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