HomeMy WebLinkAboutTract 7305 Sewer StudySEWER STUDY
Tract No. 7305
Objective
The objective of this study is as follows:
1) The purpose of this study is to determine the sewer discharge from Tract 7305 and to
determine if any surrounding areas may be served by two main lines on Panama Lane.
Existing Facilities
The site is currently undeveloped and surrounded by undeveloped land to the south and west
with Cactus Patch Drive to the east. Tract 7262 is planned for the land to the west and Tract
7263 is planned for the land to the south. Panama Lane exists to the north with an existing 8”
sewer stub from the intersection of Reliance Drive. The downstream system is an existing
18” sewer main on Panama Lane. An existing 10” sewer line runs northerly along Cactus
Patch Drive to Panama Lane. This line is upstream of an existing 12” sewer main on Panama
Lane.
Planned Land Uses
Tract 7305 is a residential duplex development (R-2) and will consist of 86 lots with two
separate connection points to the existing sewer. The dwelling units per lot was assumed to
be 3.9 with an average lot size of 7,600 sq. ft.
Phasing
The project consists of two phases with two separate sewer systems. The Phase 1 sewer
system services 48 duplex lots (12.70 acres – 188 EDUs) and Phase 2 handles 38 duplex lots
(10.23 acres– 149 EDUs). [Refer to the attached Sewer Exhibit]
Design
Phase 1 will include four lots from Phase 2 entering into this sewer system. This phase of the
proposed development will be serviced by an existing 10” sewer located on the easterly side
of Cactus Patch Drive, just south of Panama Lane. Phase 2 will discharge westerly towards
Reliance Drive and tie into an existing 8” sewer stub off Panama Lane. Due to the terrain and
cover restrictions, we are proposing to construct 8” PVC sewer lines at a slope of 0.25%.
Our calculations, shown below and in the enclosed spreadsheet, show that the proposed 8”
line will work. Phase 1 for Tract 7305 with four additional lots is expected to generate 0.26
cfs of sewer. The remaining part of the tract, Phase 2, will generate a flow of 0.21 cfs, shown
in Pipe 2. The overall discharge produced for the developed condition is 0.470 cfs.
V = 1.486 R2/3S1/2 and Q = AV
n
Where “V” is the average velocity in feet per second
“n” is Manning’s coefficient
“A” is the area based on the pipe size
For plastic pipe: n = 0.011
1.486 = 135.091
n
“R” is the hydraulic radius in feet and “S” is the slope in feet per foot.
Sewer Main Allowable Flow Characteristics
8” @ 0.250% V = 135.091 x 0.304 x 0.050 = 2.053 fps
A = 0.349 sf
Q = 0.72 cfs
Calculations are attached in spreadsheet form.
Results
Tract 7305 has been divided into two phases and the sewer has been designed to serve each
phase as proposed. It is calculated that the project will generate 0.470 cfs of sewer. The
system is designed to use 8” PVC pipe at 0.25% throughout most of the site. The last 100 feet
of all reaches are 6” PVC at 1%. The site discharges at two separate points of connection on
Cactus Patch Drive and on Reliance Drive. The connection for Phase 1 system is at an
existing manhole on the west side of Cactus Patch Drive, an invert elevation of 346.36’. This
discharge will ultimately drain into the Ashe Road Trunk which located adjacent to the
Existing Winco Store site. Phase 2 will discharge into an existing 8” stub (connection point
of 346.40’ inv. elevation) at the intersection of Panama Lane and Reliance Drive. This
discharge will ultimately drain into the Gosford Road Trunk line which discharges to the
Wastewater Treatment Plan No 3.
The sewer systems within the tract is shallow. We are able to provide minimum cover by
using PVC pipe and minimizing the slope of the pipe to 0.25%. The two sewer systems can
service Tract 7305.
C.E.Q.A. Compliance
Development of the proposed project will not result in significant impacts to the existing and
proposed sewer collection and treatment facilities. The development will be serviced by the
City of Bakersfield’s Wastewater Treatment Plant No. 3 which currently has a capacity of
32.0 million gallons per day.
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Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Wednesday, Feb 13 2019
Flow from Phase 1 - 48 Lots (188 D.U.)>
Circular
Diameter (ft) = 0.67
Invert Elev (ft) = 1.00
Slope (%) = 0.25
N-Value = 0.011
Calculations
Compute by: Known Q
Known Q (cfs) = 0.26
Highlighted
Depth (ft) = 0.28
Q (cfs) = 0.260
Area (sqft) = 0.14
Velocity (ft/s) = 1.85
Wetted Perim (ft) = 0.94
Crit Depth, Yc (ft) = 0.24
Top Width (ft) = 0.66
EGL (ft) = 0.33
0 1
Elev (ft)Section
0.75
1.00
1.25
1.50
1.75
2.00
Reach (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Wednesday, Feb 13 2019
Flow from Phase 2 - 38 Lots (149 D.U.)>
Circular
Diameter (ft) = 0.67
Invert Elev (ft) = 1.00
Slope (%) = 0.25
N-Value = 0.011
Calculations
Compute by: Known Q
Known Q (cfs) = 0.21
Highlighted
Depth (ft) = 0.25
Q (cfs) = 0.210
Area (sqft) = 0.12
Velocity (ft/s) = 1.75
Wetted Perim (ft) = 0.88
Crit Depth, Yc (ft) = 0.22
Top Width (ft) = 0.65
EGL (ft) = 0.30
0 1
Elev (ft)Section
0.75
1.00
1.25
1.50
1.75
2.00
Reach (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Wednesday, Feb 13 2019
Maximum flow at - depth(at peak flow condition): Pipe 2>
Circular
Diameter (ft) = 0.67
Invert Elev (ft) = 1.00
Slope (%) = 0.25
N-Value = 0.011
Calculations
Compute by: Known QM
Max. Allow Q (cfs) = 0.70
Highlighted
Depth (ft) = 0.53
Q (cfs) = 0.700
Area (sqft) = 0.30
Velocity (ft/s) = 2.34
Wetted Perim (ft) = 1.47
Crit Depth, Yc (ft) = 0.40
Top Width (ft) = 0.54
EGL (ft) = 0.61
0 1
Elev (ft)Section
0.75
1.00
1.25
1.50
1.75
2.00
Reach (ft)
PIPE 28
10 :
PHASE 1PHASE 2
PHASE 1PHASE 2
PHASE 1PHASE 2
PART OF THE PHASE 1 SEWER SYSTEM
NOTE: