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CITY OF BAKERSFIELD
PUBLIC WORKS DEPARTMENT
SEWER STUDY
FOR
WASTE WATER TREATMENT PLANT #3
TRUNK SEWER CAPACITY
PHASES 1 & 2
April 8, 2014
Prepared By
Meyer Civil Engineering, Inc.
INDEX
PURPOSE AND SUMMARY ........................................................................................... 1
DESCRIPTION OF EXISTING SEWER SYSTEMS ........................................................ 2
SEWER LOADINGS ........................................................................................................ 2
SCENARIO 1 – EXISTING FLOWS AND EXISTING SEWERS ..................................... 3
SCENARIO 2 – FUTURE FLOWS AND EXISTING SEWERS ........................................ 3
SCENARIO 3 – FUTURE FLOWS WITH SEWER IMPROVEMENTS ............................ 4
CONCLUSIONS AND RECOMMENDATIONS ............................................................... 5
APPENDIX A – LOADINGS SUMMARY AND STUDY MAP ........................................... 7
APPENDIX B – SCENARIO 1 CALCULATIONS AND RESULTS ................................... 8
APPENDIX C – SCENARIO 2 CALCULATIONS AND RESULTS .................................. 9
APPENDIX D – SCENARIO 3 CALCULATION AND RESULTS ................................... 10
APPENDIX E – COST ESTIMATE ................................................................................ 11
APPENDIX F – SUPPORTING DOCUMENTS ............................................................. 12
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PURPOSE AND SUMMARY
The purpose of this study is to determine the available capacities for two trunk sewers
servicing Waste Water Treatment Plant No. 3 (WWTP#3) and provide recommended
improvements to mitigate future loadings. The two trunk sewers studied are the Allen
Road Trunk Sewer and the Buena Vista Trunk Sewer. Phase 1 of this study analyzed
the Allen Road Trunk Sewer and Phase 2 of this study analyzed the Buena Vista Trunk
Sewer. This report combines both Phase 1 and Phase 2 into one comprehensive study.
The service areas for both the Allen Road Trunk Sewer and the Buena Vista Trunk
Sewer encompass the majority of the west Bakersfield Metropolitan area. Currently, the
majority of the areas serviced by both trunks are within the City limits; however a few
areas outside of the City limits are being serviced. Existing sewer service areas were
determined from as-built sewer plans. Future sewer service areas were determined
from information provided in the CSA-71 Sewer Master Plan revised March 2004. This
master plan outlines sewer service areas for County Planned Sewer Area No. 71 (CSA-
71). CSA-71 is approximately 73.3 square miles located northwest of central
Bakersfield. A portion of CSA-71 areas outside of the City limits are slated to be
serviced by the City of Bakersfield, the remaining area is to be serviced by North of the
River Sanitary District No. 1 (NOR). There are five of these areas called City Planned
Sewer Areas. Please see the map in Appendix A, Sewer Service Area for a better
understanding of entire study area, trunk alignments, and individual service areas.
Furthermore, Agreement No. 00-11 between the City of Bakersfield and NOR outlines
the areas north of the Kern River that are to be serviced by the City. The CSA-71
Sewer Master Plan conforms to this agreement and was the basis for determining future
service areas for this study.
Existing as-built sewer plans and City standards for sewer loadings, in conjunction with
existing and future sewer service areas, were used to create and compile multiple
sewer models in the program SewerCAD V8i by Bentley Systems to reflect different
scenarios. Three scenarios were analyzed:
1. Existing Flows and Existing Sewers – This scenario analyzed the current sewer
system under existing sewer loadings.
2. Future Flows and Existing Sewers – This scenario analyzed the current sewer
system under future sewer loadings.
3. Future Flows and Sewer Improvements – This model analyzed the current and
proposed (per this study) sewer system under future sewer loadings to provide
the entire system with adequate capacity.
In summary, the Buena Vista Trunk Sewer system under existing loadings only has
capacity for an additional 7,000 Single Family Dwelling Units (18,200 persons). Also,
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portions of the Allen Road Trunk Sewer lack capacity for the existing flows. Also, the
Allen Road Trunk Sewer Lift Station located on White lane is at or near capacity for the
existing flows. In addition, both the existing Allen Road Trunk Sewer and Buena Vista
Trunk Sewer systems are inadequate to convey the future sewer loadings. Proposed
improvements and associated cost estimate have been included herewith.
DESCRIPTION OF EXISTING SEWER SYSTEMS
Allen Road Trunk Sewer – The Allen Road Trunk Sewer is located west of the Buena
Vista Trunk Sewer and services portions of northwest and southwest Bakersfield. The
sewer begins north of Noriega Road and travels south along Allen Road. Near the
intersection of Allen Road and Hageman Road the sewer flows into the Hageman No. 1
Lift Station. From this lift station the sewer continues to travel south along Allen Road,
crossing the Kern River, to the intersection of S. Allen Road and White Lane. From this
intersection the sewer travels east along White Lane to the Allen Road Trunk Sewer Lift
Station. This lift station was designed and constructed with a spare wet well to be used
for future expansion. From this lift station the sewer continues to flow east to the
intersection of White Lane and Buena Vista Road where it is then intercepted by the
Buena Vista Trunk Sewer.
Buena Vista Trunk Sewer – The Buena Vista Trunk Sewer is located east of the Allen
Road Trunk Sewer and services the remaining portions of northwest and southwest
Bakersfield not serviced by the Allen Road Trunk Sewer. The sewer begins in
northwest Bakersfield and travels south along Buena Vista Road to the intersection of
White Lane and Buena Vista Road. Only the portion downstream of White Lane was
analyzed for this study; however, upstream sewer loadings were taken into account. At
White Lane the sewer receives flows from the Allen Road Trunk Sewer and continues to
travel south along Buena Vista Road to the intersection of McCutchen Road and Buena
Vista Road. From this intersection the sewer flows east along McCutchen Road to
Gosford Road where the sewer combines with a 60” sewer that travels east to the
McCutchen/Gosford Lift Station. It should be noted that the City intends to build a
diversion manhole on the Buena Vista Trunk Sewer at the intersection of Buena Vista
Road and White Lane to divert a fraction of the flows to the east in the existing 30”
White Lane Sewer.
SEWER LOADINGS
The City Standards for sewer loadings apply. It is the opinion of this engineer and City
staff that only residential loadings were to be considered for this study due to the size of
the entire service area. This is because accounting for commercial, schools, industrial,
and other non-residential zones along with residential zones for such a large service
area would result in double accounting and grossly overestimate the sewer flows.
Therefore, zoning data and property parcels were used to determine the number of
Single Family and Multi Family dwelling units. Please see the sewer loading criteria
below:
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Single Family Dwelling:
Multi Family Dwelling:
2.6 persons at 100 gallons per person per day average
2.0 persons at 100 gallons per person per day average
Peaking Factor: Pf=2.65x(Average Discharge)-0.1 for flows in CFS
Please see the table in Appendix A, Loadings Summary for a detailed table of service
areas and the corresponding sewer loadings.
Population calculations based on the City Standards checked closely with GIS
population data provided by the City.
SCENARIO 1 – EXISTING FLOWS AND EXISTING SEWERS
This scenario modeled the current sewer system under existing loadings. Please see
Appendix B for a table regarding conduit information and profiles depicting the sewers
for this scenario.
This scenario determined that the current system under existing flows performs
adequately with one exception. A portion of the Allen Road Trunk Sewer is undersized.
This undersized 15” sewer is from just downstream of Rosedale Highway to Palm
Avenue. The undersized sewer causes flows to backup upstream. As such, the portion
of sewer downstream of the Hageman No. 1 Lift Station to Palm Avenue is flowing
under surcharged head. A solution to this is modeled and discussed in Scenario 3.
Under this scenario the current Allen Road Trunk Sewer downstream of Palm Avenue
has available capacity to increase service; however, this is limited by the existing
available capacity in the Allen Road Trunk Sewer Lift Station. The Allen Road Trunk
Sewer Lift Station located on White Lane is at or near capacity.
The current Buena Vista Trunk Sewer has a remaining capacity of 7,000 Single Family
Dwelling Units (18,200 persons). If the City were to construct a 7.5 CFS bypass
manhole at White Lane and Buena Vista Road then capacity would increase an
additional 8,000 Single Family Dwelling Units (20,800 persons).
SCENARIO 2 – FUTURE FLOWS AND EXISTING SEWERS
This scenario modeled the current sewer system under future loadings. Please see
Appendix C for a table regarding conduit information and profiles depicting the sewers
for this scenario.
This scenario determined that the current system under future flows is severely
inadequate. The model shows that almost all portions of the Allen Road Trunk Sewer
and Buena Vista Trunk Sewer are under surcharged head. However, the Allen Road
Trunk Sewer flows under surcharged head because the Allen Road Sewer Lift Station is
insufficient to convey the flows; the sewer lines themselves have capacity, except for
the 15” line discussed under Scenario 1. Under this scenario the Buena Vista Trunk
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Sewer flows under surcharged head because the downstream reach is nearly flat and,
therefore, lacks capacity to carry the flows. A solution to the lack of capacity for both
systems is modeled and discussed in Scenario 3.
SCENARIO 3 – FUTURE FLOWS WITH SEWER IMPROVEMENTS
This scenario modeled the current and proposed sewer system improvements under
future loadings. Please see Appendix D for a table regarding conduit information and
profiles depicting the sewers for this scenario. Please see below for brief descriptions
of the proposed sewer improvements modeled in this scenario.
Allen Road Trunk Sewer
As stated in Scenario 1, a portion of the Allen Road Trunk Sewer is undersized for
existing flows and requires upsizing to carry existing and future flows. The proposed
solution for this reach of sewer is to:
Replace the upstream 800 linear feet of the 15” sewer with an 18” sewer.
Replace the remaining downstream 1700 linear feet of the 15” sewer with a 24”
sewer.
Allen Road Sewer Lift Station
The existing Allen Road Sewer Lift Station located on White Lane requires capacity
improvements to convey future flows. Proposed improvements utilize the existing spare
wet well and include pump and manifold upgrades. Currently, the sole operating wet
well has three pumps, all of which are operating during the peak flow of 9 CFS. Future
peak flows into the lift station are modeled as 23 CFS. The proposed solution for the lift
station is to:
Remove the existing 3 pumps and install 3 new pumps in each wet well, 6 pumps
total. One pump per wet well is for redundancy.
Remove existing 8” manifold piping and install 10” piping for both wet wells.
Modify sewer upstream to split flows evenly to each wet well.
White Lane and Buena Vista Road Diversion Manhole
In order for all suggested improvements to work effectively, the City proposed diversion
manhole at White Lane and Buena Vista Road must be implemented. And, the
manhole should be designed to divert 7.5 CFS out of the Buena Vista Trunk Sewer to
the 30” White Lane sewer.
Buena Vista Trunk Sewer Diversion Manhole and McCutchen Road Trunk Sewer
The most crucial component of these sewer improvements is the proposed diversion
manhole on the Buena Vista Trunk Sewer and proposed McCutchen Road Trunk
Sewer. These proposed improvements include:
Construct a diversion manhole on the existing Buena Vista Trunk Sewer just
downstream of Harris Road. This diversion manhole is to divert 8.2 CFS into the
new McCutchen Road Trunk Sewer.
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Construct the McCutchen Road Trunk Sewer parallel to the existing Buena Vista
Trunk Sewer. This new sewer is to carry flows from the diversion manhole and,
where feasible, receive existing and future flows that would have otherwise
surcharge the Buena Vista Trunk Sewer. This new trunk would terminate where
the Buena Vista Trunk Sewer becomes a 60” sewer.
CONCLUSIONS AND RECOMMENDATIONS
Development within the study area is once again becoming active. With this in mind,
project planning should now commence for the construction of the recommended
facilities.
Per this study the future sewer loadings applied to the existing sewer system indicate a
severe lack of capacity for both the Allen Road Trunk Sewer system and the Buena
Vista Trunk Sewer System. Additionally, portions of the existing Allen Road Trunk
sewer are undersized for the existing sewer loads and no remaining capacity exists in
the existing Allen Road Trunk Sewer Lift Station on White Lane. The existing Buena
Vista Trunk Sewer system only has capacity for an additional 7,000 Single Family
Dwelling Units (18,200 persons). However, capacity for an additional 8,000 Single
Family Dwelling Units (20,800 persons) is available if the diversion manhole at Buena
Vista Road and White Lane is constructed. With just the diversion manhole
constructed, the Buena Trunk Sewer capacity becomes 15,000 Single Family Dwelling
Units (39,000 persons).
Unfortunately, the construction of the diversion manhole at White Lane and Buena Vista
Road does not offset the future sewer loadings, capacity issues still arise.
Recommended sewer improvements to mitigate all future flows are listed below:
Remove and replace existing 15” Allen Road Trunk Sewer with an 18” and 24”
sewer to alleviate current surcharging between Hageman Road and Palm Ave.
Construct diversion manhole at White Lane and Buena Vista Road to divert some
flows to the 30” White Lane sewer.
Upgrade Allen Road Sewer Lift Station to handle increased future flows.
Construct diversion manhole on the Buena Vista Trunk Sewer to alleviate
surcharging in the Buena Vista Trunk Sewer
Construct McCutchen Sewer parallel to existing Buena Vista trunk sewer to
convey diverted flows from diversion manhole listed above, and intercept feasible
future and existing flows that would otherwise contribute to the Buena Vista
Trunk Sewer.
The breakdown costs for the project are summarized below:
McCutchen Road Trunk Sewer…………………………………………$9.6 million
Allen Road Trunk Sewer Improvements…………………………….....$2.4 million
Buena Vista Rd. & White Ln. Diversion Manhole……………………..$51,400
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The total estimated cost of the all listed projects is $12,060,000. For a detailed
preliminary cost estimate please see Appendix E.
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APPENDIX A – LOADINGS SUMMARY AND STUDY MAP
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APPENDIX B – SCENARIO 1 CALCULATIONS AND RESULTS
Existing Flows and Existing Sewers
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APPENDIX C – SCENARIO 2 CALCULATIONS AND RESULTS
Future Flows and Existing Sewers
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APPENDIX D – SCENARIO 3 CALCULATION AND RESULTS
Future Flows and Sewer Improvements
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APPENDIX E – COST ESTIMATE
12
APPENDIX F – SUPPORTING DOCUMENTS
Agreement No. 00-11
CSA-71 Master Plan, City Planned Sewer Areas