HomeMy WebLinkAboutParcel Map 12271 Drainage StudyCommercial Development - Drainage Study 542-08
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Purpose: Calculate the runoff volume of the surrounding streets on the commercial
development site located in the southeast corner of Panama Lane and Gosford
Road in the City of Bakersfield to determine the volume required for each of the
two on-site temporary retention basins.
Order of Work: The existing condition of the site is undeveloped. There are no on-site
improvements proposed at this time. Privately maintained temporary sumps are
proposed to retain the runoff from Gosford and Panama as part of the Street
Improvement Plans.
Approach: The following assumptions will be used to determine the required volumes of the
temporary retention basins.
a. Volume of runoff for areas shown in Figure 1.
b. Retention required for the runoff.
c. Design of temporary retention basins.
Assumptions: The following information was assumed to apply to this study:
a. Areas for the temporary retention calculations are shown in Figure 1 and
based on the off-site street plans for Panama Lane and Gosford Road.
b. The runoff coefficient used is as follows:
0.95 asphalt pavement
(Based on City of Bakersfield Design Manual)
Calculations: V=0.15*SUM(C*A)
(From the City of Bakersfield Department of Public Works Subdivision and
Engineering Design Policy Manual)
Conclusion: Total volume required for the two temporary retention basins is 8,039 cubic feet
(0.19 acre-feet) for “A1” and 1,639 cubic feet (0.04 acre-feet) for “A2” per Table
1. The designed temporary retention basins will provide approximately 17,773
cubic feet (0.41 acre-feet) for “A1” and 1,757 cubic feet (0.04 acre-feet) for “A2”
as shown in Figure 1. Therefore, the capacities of the designed temporary
retention basins are adequate to retain the required runoff. The runoff shown in
drainage area 4 will drain to a nearby catch basin that connects to a storm drain
system that outflows everything to an on-site sump designed in the previously
Commercial Development - Drainage Study 542-08
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approved storm drain plans for Tract 7261 (sheet 9 of storm drain plans are
attached at the end of this study). Table 2 shows the volume calculations based on
the Tract 7261 Master Drainage Study/Drainage Exhibit (attached to the end of
this study) assuming that all of the commercial site and adjacent streets will drain
to the Tract 7261 on-site sump. Table 3 shows the impact that Drainage Area 4
has on the Tract 7261 on-site sump. Drainage Area 4 will merge with Area 2 from
the Tract 7261 Master study as shown in Table 3. Since the volume required
calculated in Table 3 is less than the volume required calculated in Table 2, Tract
7261 on-site sump will handle the runoff from the drainage areas shown in Figure
1. The calculated sump volume required value from Table 3 has to do with
Drainage Areas 1, 2, and 3 being retained in the two on-site temporary retention
basins separate from the Tract 7261 approved storm drain system that had
incorporated them in Table 2. The curb capacity calculations for a 5 year event on
Wynnfield Lakes in Table 4 shows that the drainage will not reach over the top of
curb and onto the sidewalk.
Commercial Development - Drainage Study 542-08
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Table 1
Temporary Retention Basin A1
Land Type Area
(sf)
Area
(Acres)
Runoff
Coefficient
(C)
CxA
(sf)
Area 1 13,216 0.30 0.95 12,555
Area 2 43,359 1.00 0.95 41,191
Cumulative CxA 53,746
Total Volume Required (CF) V=0.15*CUM(CxA) 8,062
Total Volume Required (AC FT) 0.19
Temporary Retention Basin A2
Land Type Area
(sf)
Area
(Acres)
Runoff
Coefficient
(C)
CxA
(sf)
Area 3 11,500 0.26 0.95 10,925
Cumulative CxA 10,925
Total Volume Required (CF) V=0.15*CUM(CxA) 1,639
Total Volume Required (AC FT) 0.04
Commercial Development - Drainage Study 542-08 4 Table 2 Sewer and Storm Drain Plans for Tract 7261 Phase 1 to 4 Calculated Values (See attached drainage exhibit) Area C A (acres) C*A Area C A (acres) C*A 1 0.4 1.99 0.80 A 0.62 4.94 3.06 2 0.4 1.76 0.70 B 0.52 1.87 0.97 3 0.59 3.13 1.85 C 0.38 5.28 2.01 4 0.4 2.32 0.93 D 0.38 2.51 0.95 5 0.4 4.63 1.85 E 0.38 3.58 1.36 6 0.4 3.66 1.46 F 0.38 3.47 1.32 7 0.4 3.37 1.35 G 0.38 3.58 1.36 8 0.4 2.06 0.82 H 0.38 3.38 1.28 COMMERCIAL 0.91 9.61 8.75 I 0.38 2.39 0.91 R‐3/R‐4 0.8 7.87 6.30 J 0.38 2.15 0.82 0.15*SUM(CA) 3.72 K 0.53 1.53 0.81 L 0.65 2 1.30 0.15*SUM(CA) 2.42 Volume Required Total (AC‐FT) 6.14
Commercial Development - Drainage Study 542-08 5 Table 3 Sewer and Storm Drain Plans for Tract 7261 Phase 1 to 4 Modified Commercial Area Values Area C A (acres) C*A Area C A (acres) C*A 1 0.4 1.99 0.80 A 0.62 4.94 3.06 M (Area 2+DA 4) 0.59* 2.66 1.56 B 0.52 1.87 0.97 3 0.59 3.13 1.85 C 0.38 5.28 2.01 4 0.4 2.32 0.93 D 0.38 2.51 0.95 5 0.4 4.63 1.85 E 0.38 3.58 1.36 6 0.4 3.66 1.46 F 0.38 3.47 1.32 7 0.4 3.37 1.35 G 0.38 3.58 1.36 8 0.4 2.06 0.82 H 0.38 3.38 1.28 R‐3/R‐4 0.8 7.87 6.30 I 0.38 2.39 0.91 0.15*SUM(CA) 2.54 J 0.38 2.15 0.82 K 0.53 1.53 0.81 DA 4 (From Figure 1) 0.90 L 0.65 2 1.30 Volume Required Total (AC‐FT) 4.96 0.15*SUM(CA) 2.42 Note: * Weighted coefficient
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Table 4
Source: FHWA Hydraulic Engineering Circular No. 22, Second Edition
Q = CIA (0.95)*(1.5)*(0.90) = 1.28
Q 1.28
A (Area of DA 4) = 0.90 acres
C = 0.95
I = 1.5
n 0.016 (based on 5 year intensity vs duration
Sx 0.02 curve from City Standard Detail D‐1 at
SL 0.006 10 minutes duration)
T 8.75
T 8.75
Sx 0.02
d 0.175
d (depth [in]) 2.10
Commercial Development - Drainage Study 542-08 7 Table 5 Tract 7261 Catch Basin 10 year Event Calculations Cw 2.3 C 0.95 (Based on City of Bakersfield Design Manual for Asphalt) L 3.5 I 1.8 (Based on 10 year intensity bs duraction curve from City Standard Detail D‐1 at 10 minutes duration) W 2 A 0.9 (From Area "DA 4" from Figure 1 of Drainage Study) d 0.67 Q =CIA Q = Cw(L+1.8W)d1.5 1.54 cfs 8.89 cfs 50% clogged 0.5Q = 4.44 cfs Flow rate of 1.54 cfs at 10 year‐10 minute duration is less than the capacity of the curb opening inlet of 4.44 cfs at 50% clogged which indicates that the inlet has enough capacity to hold at a 10 year storm event. Equation from website: https://learn.hydrologystudio.com/stormwater‐studio/knowledge‐base/inlets‐in‐sags/
Commercial Development - Drainage Study 542-08 8 Figure 1