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Home My WebLink AboutSanitary Sewer System Design Report a • SANITARY SEWER SYSTEM ENGINEERING DESIGN REPORT SPRING CREEK TERRACE PHASE ONE COLLEGE STATION, BRAZOS COUNTY, TEXAS MAY, 2011 ,oF r4 , if � . . te r „. `.'0 ‘ ..,: i MICHA L E G. HESTER - o. 69104 .*�f _ p., S S/4NA' THE SEAL APPEARING ON THIS DOCUMENT WAS AUTHORIZED BY MICHAEL G. HESTER, P.E. #69104 MAY 11, 2011 RELEASED FOR RECORD Submitted By: Michael G. Hester, P.E. HESTER ENGINEERING COMPANY #F -3476 7607 Eastmark Drive, Suite 253 -B College Station, TX 77840 (979) 693 -1100 Sanitary Sewer System Engineering Design Report SPRING CREEK TERRACE PHASE ONE COLLEGE STATION, BRAZOS COUNTY, TX MAY, 2011 INTRODUCTION: The proposed development is located adjacent to the the intersection of Decatur Drive and Dayton Court and will connect to Whispering Creek Drive. The development is bordered on the north by an undeveloped light industrial zoned tract, the west by the Shenandoah development, the east by an undeveloped commercial zoned tract and the south by Spring Creek Gardens. The legal description is Spring Creek Terrace (SCT) and is approximately 10.4 acres. The proposed improvements include pavement, drainage and utility improvements for 44 single - family residential homes. The site consists of numerous small trees and the terrain slopes in a easterly direction toward a tributary of Spring Creek at an average slope of 2- percent. The site is zoned R -1 (residential) and is being developed by JC Wall, PIL Investments, P.O. Box 390, Moody, Texas 76557, 254 - 721 -6179. The length of pipe to be installed will be 1370 linear feet of 8 -inch diameter PVC SDR26 ASTM D3034 heavy wall sanitary sewer pipe with compression type fittings. The proposed system will connect to an existing 18" sanitary sewer trunk line in a tribituary of Spring Creek that was installed by the City of College Station to serve the surrounding area and the trunk line was designed to include this proposed development. The regional system will discharge into the Lick Creek Wastewater Treatment Plant, TNRCC No. 10024 -003. The project will be reviewed for compliance with the City of College Station Subdivision Ordinances and Design Criteria for sanitary sewer systems by the City of College Station Development Engineering Division, Mr. Alan Gibbs, P.E., City Engineer, 1101 Texas Ave, College Station, TX 77842, (979)764 -3570. City of College Station representatives will inspect the construction and observe the testing of the project. The City of College Station will be the owner and maintainer of the constructed sanitary sewer system HYDRAULIC CAPACITY: Average daily flow = (44 dwelling units )(2.67cap /du)(100gpd /cap)(1 day /1440 min) - 8.15 gpm Average daily flow x 4 - 32.63 gpm adjusted Peak hourly flow The hydraulic capacity of an 8 -inch diameter pipe at the minimum allowable design slope of 0.33% is 312 gpm which is much greater than the maximum systems anticipated inflow. TESTING OF INSTALLED PIPE: Sewer pipe is tested by a low- pressure air test, manholes are tested with a vacuum of minus 10 inches of mercury for a specified time, deflection testing is performed with a mandrel sized to 5 percent smaller than the inside diameter of the line and the sewer lines are then TV'd to assure there are no low spots. BEDDING TRENCHING AND BACKFILL: Between 4" below to 6" above the pipe select sand backfill with a PI of less than or equal to 12 and less than 50 percent passing a #200 sieve is placed. The remaining backfill is excavated material compacted to a minimum of 90 percent of maximum dry density as determined by ASTM D698 at a moisture content within 2 percent of optimum moisture content. Sanitary Sewer System Engineering Design Report - Page 1 of 2 Pages . EROSION CONTROL: Sediment is maintained on the site by the use of silt fencing and hay bales in all areas of possible sediment transport. A storm water pollution control plan is included in the construction plans. DESIGN DETAILS: The minimum allowable size of sanitary sewer main in the City is 6" with a minimum design slope is 0.8 percent and an n factor of 0.13 and laid in straight alignments with uniform grade between manholes. Manholes are placed only at points of change in alignment, grade, or size of sewer, at the intersection of all sewers and the end of all sewer lines and are constructed of precast concrete, with a maximum spacing of 500 linear feet. Pipe to manhole connectors are used in the precast manholes to insure water tightness, the minimum width of the manholes is 48 ", the inverts are poured with a "U" shape channel with a bench sloped at 0.5 inch per feet and the manhole covers are a nominal 26- inch or larger diameter. TYPE OF PIPE AND ITS ANTICIPATED PERFORMANCE: The type of pipe proposed for this project is PVC SDR26 ASTM D3034 heavy wall sanitary sewer pipe with compression type fittings. PVC sewer pipe is not affected by sulfuric acid in the concentrations attained in residential sanitary sewer systems; therefore, the generation of hydrogen sulfide does not contribute to corrosion problems. The average depth of cover is eight feet and with the proposed bedding techniques the pipe should handle all loading conditions. Deflection and infiltration tests are proposed to assure the required construction and performance. AMOUNT OF INFILTRATION /INFLOW EXISTING AND ANTICIPATED: Inflow is managed by a City ordinance not allowing any sort of drain to be tied to the sanitary sewer system. Other precautions are the use of watertight manhole rings and covers in areas where storm water could get into the system. The ground water table in this area is below the proposed system and all manholes are constructed at least 0.5 feet above surrounding natural ground. Soil conditions at the site consist of primarily clays with a thin layer of loam on top. CONCLUSION With the installation of the proposed sewer lines there is more than sufficient capacity to accommodate the peak flows and any infiltration. The proposed system presented in this report is prepared with consideration given to the Texas Commission on Environmental Quality Chapter 217 °Design Criteria for Domestic Wastewater Systems" and the Cities design standards and specifications. The proposed design, installation and testing of this domestic wastewater project is in substantial compliance with TCEQ rules and no variances are planned nor requested. REFERENCES: "Design And Construction of Sanitary and Storm Sewers °, WEF Manual of Practice No. 9, ASCE Manual on Engineering Practice No. 37, 1970 °Design Criteria for Domestic Wastewater Systems' Texas Commission On Environmental Quality Sanitary Sewer System Engineering Design Report - Page 2 of 2 Pages HESTER ENGINEERING COMPANY 7607 EASTMARK DRIVE, SUITE 253 -B COLLEGE STATION, TEXAS 77840 (979) 693 -1100 email: mhester @hester - engr.com May 11, 2011 Mr. Louis C. Herrin, III, P.E. TCEQ Wastewater Permits Section P.O. Box 13087 Austin, Texas 78711 -3087 (512) 239 -1000 Re: Spring Creek Terrace Phase One College Station, Brazos County, Texas Summary Transmittal Letter DESIGN FIRM AND ADDRESS: Hester Engineering Company #f -3476 7607 Eastmark Drive, Suite 253 -B College Station, TX 77840 DESIGN ENGINEER: Michael G. Hester, P.E. #69104 979 - 693 -1100 COUNTY AND PROJECT NAME: Brazos County Spring Creek Terrace Phase One SANITARY SEWER OPERATOR: The City of College Station will own and maintain the constructed sanitary sewer system. WASTEWATER TREATMENT PLANT PERMIT NAME AND NUMBER: Lick Creek Wastewater Treatment Plant, TNRCC No. 10024 -003. COMPLIANCE STATEMENT: The plans and specifications are in substantial compliance with all requirements of TCEQ rules as found in Chapter 217 'Design Criteria for Domestic Wastewater System ", and no variances are planned nor requested. BRIEF DESCRIPTION: The proposed system will consist of 1370 linear feet of 8" diameter thick wall (ASTM D3034, SDR26) sanitary sewer line that will serve 43 single - family residential homes. The system will discharge into an existing 18" sanitary sewer trunk line that discharges into the Cities Lick Creek Wastewater Treatment Plant. The project will be reviewed for compliance with the Cities Subdivision Ordinances and Design Criteria for sanitary sewer systems by the City Engineering Division, Mr. Alan Gibbs, P.E., City Engineer, P. 0. Box 9960, College Station, TX 77842, (979) 764 -3570. If you have any questions please contact me. Respectfully Submitted, fkb-27 Michael G. Hester, P.E. xc: Frank Burleson, P.E., Water Manager, TCEQ, Region 9 Alan Gibbs, P.E., City Engineer, P. 0. Box 9960, College Station, TX 77842 Hester Engineering Company Civil Engineering Services 7607 Eastmark Drive, Suite 253 -B College Station, TX 77840 979 - 693 -1100 mhester @hester- engr.com Date Louis C. Herrin, 111, P.E. Wastewater Permits Section (MC 148) Water Quality Division Texas Commission On Environmental Quality Re: Spring Creek Terrace Texas Commission on Environmental Quality Permit # WWPR Log No. - DATE OF COMPLETION: CERTIFICATION: All construction, materials, and equipment were substantially in accordance with the approved pro the rules of the TCEQ, and any change orders filed with the TCEQ. SEAL: •. OF T r • .. - '� • 9 ti f MICHAEL G. HESTER JJ t 69104 • ��;' i1ti�F • S j0 ENS �� G\?.- - t -e Xc: Frank Burleson, P.E, TCEQ, Region 9, 6801 Sanger Ave. #2500, Waco, TX 76710 Alan Gibbs, P.E. College Station Engineering Division, P.O. Box 9960 College Station, Tx 77842