HomeMy WebLinkAbout2630 Mt Vernon - Drainage Study
15‐056 Mount Vernon Market
SPR #: 15‐526
2630 Mount Vernon Avenue
Bakersfield, CA
Drainage
Calculations
Prepared By:
Civil Design Studio, Inc.
Robert Winslow, PE
P.O. Box 199
Cambria, Ca 93428
805.706.0401
15‐056 Mt Vernon Market
Drainage Calculations Page | 1
Attn: Manny Behl
City of Bakersfield
Department of Public Works
1501 Truxton Avenue
Bakersfield, Ca 93301
Subject: Mount Vernon Market
Re: Drainage Calculations
John:
Please find enclosed the Drainage Calculations for the above referenced project.
The study calculations were prepared using the Rational Method and Mannings Equation.
Please contact me for any clarifications or supporting information you need with reference to
this report.
Regards,
Robert Winslow, PE
15‐056 Mt Vernon Market
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Contents
Introduction .................................................................................................................................................. 3
Project Location ........................................................................................................................................ 3
Proposed Project ....................................................................................................................................... 4
Drainage Calculations ................................................................................................................................... 5
Rational Method Inputs ............................................................................................................................ 5
Proposed Site Hydrology ........................................................................................................................... 5
Proposed Site Runoff ................................................................................................................................ 6
Future Site Runoff ..................................................................................................................................... 6
Pipe Analysis ............................................................................................................................................. 6
Catch Basin Analysis .................................................................................................................................. 7
Report Conclusion ..................................................................................................................................... 8
Supporting Documents ................................................................................................................................. 9
NOAA Atlas 14 Point Precipitation Frequency Rainfall Intensity .............................................................. 9
Drainage Area Map ................................................................................................................................. 10
Drainage Inlet Detail ............................................................................................................................... 11
15‐056 Mt Vernon Market
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Introduction
Project Location
The proposed project is located in the city of Bakersfield, county of Kern, state of California. The site is
bordered by Mount Vernon Avenue to the east, commercial development to the north, empty lot to the
west, and residential to the south. The site is an undeveloped lot.
Figure 1: Project Location
15‐056 Mt Vernon Market
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Proposed Project
The proposed project consists of renovating the existing Sizzler parking lot, construction of a new
building, parking lot, and trash enclosures (see civil improvement plans).
Figure 2: Proposed Project
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Drainage Calculations
Rational Method Inputs
The Rational Method will be utilized to calculate the anticipated runoff for the proposed development.
Inputs for the rational method equation include the following:
A weighted “C” calculation will be utilized to determine the “C” value for pervious and impervious areas,
for post development.
The site area tributary to the existing storm drain system has been measured at 5.75 acres. This includes
the property being improved and the tributary parking lots/buildings to the north. See attached
Drainage Area Map.
The rainfall intensity is determined from a figure (included) provided by the NOAA Hydrometeorological
Design Studies Center, Atlas 14 Point Precipitation Frequency Estimates: CA. The value used for this
calculation is for a 10 year 24 hour storm. This value is 1.74 inches.
Proposed Site Hydrology
The proposed site consists of renovating the existing Sizzler parking lot, construction of a new building,
parking lot, and trash enclosures. The following table shows how the weighted “C” value was calculated.
Weighted “C” Value – Area “A”
Area Description Area, ac "C”
Value
Product of “C”
and Area
Impervious 0.8 0.9 0.72
Pervious 1.4 0.3 0.42
Totals 2.2 n/a 1.14
Weighted "C" 0.52
Weighted “C” Value – Area “B”
Area Description Area, ac "C”
Value
Product of “C”
and Area
Impervious 1.5 0.9 1.35
Pervious 0.1 0.3 0.09
Totals 1.6 n/a 1.44
Weighted "C" 0.90
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Weighted “C” Value – Area “C”
Area Description Area, ac "C”
Value
Product of “C”
and Area
Impervious 1.1 0.9 0.99
Pervious 0.8 0.3 0.24
Totals 1.9 n/a 3.79
Weighted "C" 0.65
Proposed Site Runoff
The proposed site runoff is collected via concrete curb and gutter and v‐gutter improvements and
directed to an existing storm drain system that discharges into a basin to the north.
Q (Site Peak Flow Rate) = C (Runoff Coefficient) * I (Rainfall intensity) * A (Site Area)
QArea A = 0.52 * (1.74 in) * 2.2 acres = 2.0 cfs
QArea B = 0.90 * (1.74 in) * 1.6 acres = 2.5 cfs
QArea C = 0.65 * (1.74 in) * 1.9 acres = 2.2 cfs
Future Site Runoff
Although the empty lot to the west hasn’t been developed yet, calculations for that runoff need to be
calculated in order to make sure the existing 21” line can handle the future flow. Assuming the future
development will connect to the existing 21” line (downstream of the proposed improvements), and
have a “C”‐Value of 0.90, the total expected stormwater runoff will be
Q (Site Peak Flow Rate) = C (Runoff Coefficient) * I (Rainfall intensity) * A (Site Area)
QTotal = 0.90 * (1.74 in) * 5.75 acres = 9.0 cfs
Pipe Analysis
Using Mannings Equation, each of the pipes maximum flowrates were calculated to make sure they can
handle the design flowrates. The maximum flowrates each pipe can handle are:
Proposed 6” PVC SDR 35 @ 1% min = 0.73 cfs
Proposed 12” HDPE Double Wall @ 0.5% = 3.28 cfs
Proposed 18” HDPE Double Wall @ 0.5% = 9.66 cfs
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Catch Basin Analysis
Since Area “B” has the highest flowrate of stormwater runoff, it will be analyzed to make sure the Mid
State Concrete Go Curb Inlet (see attached) can handle the design storm. To include a safety factor, the
catch basins were analyzed assuming they were 50% clogged with debris. Autodesk Storm and Sanitary
Analysis 2015 was used for the calculations. See below:
Autodesk Storm and Sanitary Analysis 2015
Drainage of Highway Pavements
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Date: 11/28/2016
Input Data
‐‐‐‐‐‐‐‐‐‐
Inlet Type: Combinational Inlet Type
Inlet Location: On Sag
Combinational Inlet Type: Curb Opening & Grate
Curb Opening & Grate Type: Equal Length Inlet
Grate Type: Parallel Bar P‐1‐1/8
Cross Slope L. Depression
Pavement Cross Slope (ft/ft) 0.0200
Manning's Coefficient 0.0110
Gutter Cross Slope (ft/ft) 0.0110
Gutter Width (ft) 2.0000
Gutter Depression (ft) 0.1700
Discharge (cfs) 2.5000
Grate Length (ft) 3.00
Grate Width (ft) 2.00
Curb‐Opening Length (ft) 3.00
Curb‐Opening Height (ft) 0.50
Output Data
‐‐‐‐‐‐‐‐‐‐‐
Gutter Spread (ft) 12.9914
Depth of Flow (ft) 0.325
Depth at Curb (ft) 0.430
Intercepted Flow (cfs) 2.500
Inlet Intercepted Flow (%) 100.00
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Report Conclusion
The proposed storm drain infrastructure can handle the runoff from the proposed development.
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Supporting Documents
NOAA Atlas 14 Point Precipitation Frequency Rainfall Intensity
Latitude: 35.3932o Longitude: ‐118.9689o Elevation: 606.44 ft
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Drainage Area Map
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DRAINAGE AREA MAP
PROJECT LOCATION:
DOLLINGER PROPERTIES
555 TWIN DOLPHIN DRIVE SUITE 600
REDWOOD CITY, CA 94065
2630 MOUNT VERNON AVENUE
BAKERSFIELD, CA 93306
PROJECT OWNER:
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Drainage Inlet Detail