HomeMy WebLinkAboutTract 6892 Sewer Study
SEWER STUDY
Tract No. 6892
Objective
The objective of this study is as follows:
1) The purpose of this study is to determine the sewer discharge from Tract 6892 and to
determine if any surrounding areas may be served by a main line extension.
Existing Facilities
The site is currently undeveloped and surrounded by undeveloped land to the south and west
with canal, rail road tracks, and a residential subdivision to the east. Tract 7153 is planned
for the land to the south and tract 6939 is planned for the land to the west. Redbank Road
exists to the north. One hundred thirty lots of Tract 6892 will discharge to an existing 42-
inch sewer line, part of the Northeast Trunk Sewer, and ultimately to the Wastewater
Treatment Plant #2.
Planned Land Uses
Tract 6892 is a residential development and will consist of 130 single family dwellings.
Phasing
The project consists of three phases. Phase 1 contains 32 single family homes plus the
possible future development of the drill site. Phase 2 contains 54 single family homes and,
Phase 3 contains 44 single family homes.
Design
The proposed development will be serviced by an existing 42” sewer located on the south
side of Redbank Road, just east of S. Fairfax Road. The existing 42” sewer was constructed
as part of Northeast Trunk Line. Due to the terrain and cover restrictions, we are proposing
to construct some of the 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. Tract 6892 is expected to generate 0.198 cfs of sewer. Due to the terrain and
limited cover of the proposed 8” line, this system cannot provide service to any other area
outside of this tract.
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 0.303 x 0.050 = 2.047 fps
A = 0.349 sf
Q = 0.714 cfs
Calculations are attached in spreadsheet form.
Results
Tract 6892 has been divided into 3 phases and the sewer has been design to serve each phase
as it is constructed. It is calculated that the project will generate 0.198 cfs of sewer. The
system is designed to use 8” PVC pipe at 0.35% throughout most of the site, except for some
areas that will require us to use a slope of 0.25%. The last 100 feet of all reaches are 6” PVC
at 1%. The site discharges to an existing manhole on the south side of Redbank Road, an
invert of 400.97 will be used at this connection point. This manhole was constructed in 2010
as part of the Northeast Trunk Sewer which discharges to the Wastewater Treatment Plant
No 2.
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. 2 which currently has a capacity of
25.0 million gallons per day.
Blaine Neptune
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