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HomeMy WebLinkAboutSewer Study TR 7261, 7262, 7263, 7305SEWER STUDY Proposed Commercial Lot, Proposed R-2 Development, and Tracts 7261, 7262, 7263, & 7305 Objective The objective of this study is as follows: To determine the sewer discharge at each point of connection to the existing 42” sewer along Gosford Road or existing 12” sewer along Panama Lane. To provide a sewer system in accordance with the City of Bakersfield requirements and guidelines. To provide an economical and reasonable design for sewer conveyance. Existing Facilities The analyzed area is all located in the City of Bakersfield, CA Section 28, T.30S. R.27E. M.D.M. This area is currently undeveloped farm land bounded to the north by existing Panama Lane, to the west by existing Gosford Road, to the South by future Berkshire Road, and to the east by a 34” gas line easement, within a 60’ PG&E Easement. Sewer Analysis east of this gas line was part of the Approved Tract 6663 Sewer Study dated 8/17/15. Eight hundred and fifty seven equivalent dwelling units plus 9.62 commercial acres will discharge to the existing 42-inch Gosford Road Trunk, and ultimately to the City of Bakersfield’s Wastewater Treatment Plant #3. Planned Land Uses Tracts 7261, 7262, & 7263, are zone for low density single family residential development and will consist of 663 single family dwellings with 97 of these dwellings discharging through Tract 6663. Tract 7305 and a portion near Panama Lane and Gosford Road are zone for low medium density single family residential development which combines for 268 equivalent dwelling units (EDU). A proposed commercial area will be located on the southeasterly corner of Panama Lane and Gosford Road. Design The project analyzed in this report consists of 8 connection points to the existing sewer lines along Gosford Road and Panama Lane. Tract 7261 (Phases 1, 2, & 3) and Tract 7262 (Phases 1, 2, & 3) will discharge into Connection Point A at the intersection of Gosford Road and Canyon Trail Avenue. Connection Point B, located at the intersection of Gosford Road and Ridge Forest Drive, will handle the flow from Tract 7261 (Phases 4 & 5) and Tract 7262 (Phases 4 & 5). A 12” sewer line along Berkshire Road will capture flows from Tract 7261 (Phases 6 & 7), Tract 7262 (Phases 6, 7, & 8) and Tract 7263 (Phases 2, 4, & 6). The future commercial development will tie into an existing 8” stub off of Panama Lane, Connection Point D. Approximately 250 ft east of the this point is an existing 8” stub, Connection Point E, which will service the future R-2 development. Connection Point F, located just east the 60’ Gas Line Easement, will handle the flow from Tract 7262 (Phases 1 & 2). The western half of Tract 7305 will discharge into Connection Point G at the intersection of Panama Lane and Reliance Drive. Connection Point H, located on Cactus Patch Drive, will handle the flow from easterly side of Tract 7305. The equivalent dwelling units as summarized below. EDU per existing sewer tie-in point Connection Point A B C D E F G H Equivalent Dwelling Units 159 144 208 N/A*88**57 90 90 * EDU not calculated since area was used to obtain average discharge **Calculated based on the 8.79 acres and assuming 10 dwelling units per acre The four tracts are currently owned by the same owner is expected to be developed separately at different dates. All the connection points, except Point H, will be serviced by an existing 42” sewer trunk line that runs along the east side of Gosford Road. Due to the proposed project configuration and cover restrictions, we are proposing to construct 8” PVC sewer lines at a slope of 0.25% within the local streets of each tract. Along Berkshire Road, a 12” PVC sewer lines at a slope of 0.15% will be constructed. The discharge from Connection Point H will be serviced by the existing 30” Ashe Road sewer trunk line. The proposed area ultimately draining to the Gosford Trunk Line is expected to generate a total flow of 1.213 cfs of sewage, and the small portion draining to the Ashe Trunk is expected to generate a total flow of 0.106 cfs of sewage. Therefore, the total sewer discharge produced by entire development, as shown on the attached Sewer Exhibit, is 1.318 cfs. Although grades have not been established for the sewer system, the pipes have been modeled at a minimum slope of 0.25%. Our calculations, shown below and in the enclosed spreadsheet, show that the existing and proposed 8” sewer lines will be more then capable of servicing the proposed project. 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 = 0.71 cfs Sewer Main Allowable Flow Characteristics 8” @ 0.350%V = 135.091 x 0.303 x 0.059 = 2.415 fps A = 0.349 sf Q = 0.84 cfs Calculations are attached in spreadsheet form. Results It is calculated that the entire project will generate 1.318 cfs of sewage. Due to the existing Topography and the proposed project layout, the sewer system has been designed to utilize 8” PVC pipe at a slope of 0.25% for critical segments of the system to provide minimum cover over the pipes. At a minimum, the last 100 feet of all reaches are 6” PVC at 1.0% per the City of Bakersfield Design Standards. The proposed project discharges to an existing 42” sewer main through seven separate tie in points located along the east side of Gosford Road and east side of Panama Lane. The existing 42” Gosford Trunk connects to the McCutchen Road Trunk and ultimately to the City of Bakersfield’s Wastewater Treatment Plan No 3. The existing Plant has an average daily influent of approx. 17.3 million gallons per day with a Plant capacity of 32 million gallons per day. The proposed project will discharge an additional 0.306 million gallons per day to Plant No. 3 for treatment. 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. Blaine Neptune R.C.E. 55102 Vicinity Map NTS PROJECT AREA Vicinity Map NTS PROJECT AREA SE W E R S T U D Y Da t e : 4 / 2 7 / 1 7 PR O P O S E D C O M M E R C I A L L O T , R - 3 D E V E L O P M E N T , T R A C T S 7 26 1 , 7 2 6 2 , 7 2 6 3 , & 7 3 0 5 Min i m u m V e l o c i t y F u l l : 2 Ma n i n i n g s " n " : 0 . 0 1 Cu m u l a t . Pe a k T o t a l R e q ' d . D e s i g n Ca p a c i t y SE R V I C E La n d DE N . A R E A E . D . U . Av g . A v e r a g e A v e . R e s . P e a k Fl o w D e s i g n U . S . Re a c h Si z e S l o p e S l o p e D . S . at D e s i g n AR E A Us e DU / A C ac r e s cf s / a c F l o w , c f s Fl o w , c f s Fa c t o r cf s Fl o w , c f s IN V . le n g t h In . I N V . 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