HomeMy WebLinkAboutSanitary Sewer Design ReportJanuary 15, 2009
Ms . Erika Bridges
Engineering Department
City of College Station
1101 Texas Avenue
College Station, Texas 77842
Re: Sanitary Sewer Design Report
Public Restrooms
Northgate Area
College Station, Texas
Gessner Engineering Job No.: 08-0256
Dear Ms . Bridges:
This letter shall serve to meet the requirements of a Sanitary Sewer Design Report,
showing that the design of the proposed improvements meet the flow requirements of
the BCS Unified Design Guidelines Manual.
The proposed development consists of an approximately 560 square foot (sf) public
restroom facility and dumpster relocation in the Northgate Area. There is an existing
eight (8) inch PVC sanitary sewer main that runs in a south-westerly direction on a 0.4%
slope and is situated in the Patricia Street right-of-way, just south of the proposed public
restroom. This eight (8) inch main ties into a manhole and feeds an eight (8) inch main
at Boyett Street. It is unknown what the existing eight (8) inch main at G
Patricia services as this information is not available on the design
plans by McClure Engineering dated April 11 , 1997. Additionally, an
analysis of the existing system and the entire area it serves is not
within the scope of this project.
The capacity of the existing eight (8) inch sanitary sewer on 0.4%
slope , using Manning's Equation, is 494,441 .6 gallons per day (gpd).
This calculation has been attached as Appendix A. Using a peak
factor of 4 and the fixture unit method, the maximum sanitary sewer
loading for the proposed public restroom is 59,616 gpd , based on an
18 hour per day usage. The Sanitary Sewer loading calculations by
fixture count method have been attached as Appendix B. This peak
demand constitutes 12% of the capacity of the existing eight (8) inch
main at Patricia. The proposed six (6) inch service line for the new
public restroom is on a 2% grade and has a capacity, according to
Manning's Equation, of 511,892 .5 gpd, only 11.6% of which will be
utilized by the Proposed Northgate Restroom. This calculation has
been attached for reference as Appendix A.
Gessner
Engineering
1712 Southwest Pkwy
Suire I 05
College Sta tion, Texas 77840
P.O. Box 10763, 77842-0763
979.680.8840
FAX 979.680.8841
2204 S. Chappell Hill Sr.
Brenham, Texas 77833
979.836.6855
FAX 979.836.6847
We trust that this report is responsive to the city of College Station requirements. Please
contact us if you have any questions or if we can be of further assistance .
Sincerely,
GESSNER ENGINEERING
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Gessner Engineering
Appendix A:
Sanitary Sewer Line Capacity Calculations
Gessner Engineering
Sanitary Sewer Capacity Calculations
Manning's Equation:
Capacity of Existing 8 inch Sanitary Sewer line on 0.4% slope:
n= 0.013
A= 0.349 sf
R= AIP = 0.167 ft
S= 0.004
Therefore,
Q=O. 765 cfs = 494,441 .6 gpd (1 gpd= 1.5472x10"-6 cfs)
Capacity of Proposed 6 inch Sanitary Sewer Service line on 2.0% slope:
n= 0.013
A= 0.196 sf
R= AIP = 0.125 ft
S= 0.02
Therefore,
Q=O. 792 cfs = 511 ,892.5 gpd (1 gpd= 1.5472x10"-6 cfs)
Gessner Engineering
Appendix B:
Fixture Count Determination
Gessner Engineering
Fixture Unit Determination
Fixture Type Fixture Unit #of Fixture GPM/GPF Total
Value Load Fixtures in Units per GPM/GPF
Factor Project Fixture
Lavatory 2 2 4 2.2 8.8
Urinal 4 2 8 1 8
Water Closet 4 6 24 1.6 38.4
(Tank Operated)
Total Fixture Units= 36 (4 + 8+ 24)
Peak Wastewater Flow, GPM = 55.2 (8.8 + 8 + 38.4)
Peak Wastewater Flow, GPO= 59 ,616 (based on a 18 hour/ day usage)
Gessner Engineering