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Sanitary Sewer r SANITARY SEWER CAPACITY STUDY FOR WILLIAMSGATE SUBDIVISION 20.27 ACRE TRACT (VOLUME 4628, PAGE 221) CRAWFORD BURNETT LEAGUE, A -7 MDG JOB NO. 000886-3736 COLLEGE STATION, BRAZOS COUNTY, TEXAS MAY 2004 _„,....4.1 4 ,7 )c -/ - � s t.06 /o4 /of L[NWIdD S. ADAMS / ... ' 6,3351 �0 : 4 / �� / 4 0 � @L � , 2551 Texas Ave. South, Ste. A, College Station, TX 77840 ik ili. t ior :4�,C Ofc: 979.693.5359 Fax 979.693.4243 Email: mdgcstx @yahoo.com 0 @4� Project Scope and Description: The purpose of this study is to determine if capacity exists in the present College Station ro system sewer system to allow the addition o f the proposed osed sanit ary sewer y stem of the Williamsgate subdivision. The project site is located just southwest of Old Wellborn Road along Rock Prairie Road beginning 1,059 feet southwest of Old Wellborn Road. The proposed tie to the existing system is northeast of Old Wellborn Road in the Edelweiss Estates /Business Area. This area contains approximately 240 residential units and sixteen office units. Analysis of Proposed Additional Sewer Flow A conservative approach to determine the expected sewer flow from the proposed Williamsgate subdivision is to assume that total water demand equals that of sewage output. Using this assumption, a peak flow of 0.08131 cfs would be generated by the proposed subdivision. This value was computed assuming that there are 2.67 people /lot and that each person uses 60 gal /day of water. Edelweiss Area Sewer Lines and Capacity: The proposed Edelweiss Area tie -in location consists of two areas, Edelweiss Estates North and Edelweiss Business South. The first of the two areas, Edelweiss Estates North, contains approximately 240 residential units, 1 service station, and 7 office units. The assumed water usages for the area are as follows: • Residential Unit: 160.2 gal /day • Service station: 400 gal /day • Office Unit (3,000 sf): 750 gal /day These values were calculated based on published values. Using these values, residential water demand was calculated to be approximately 38,448 gal /day and business water demand at approximately 6,150 gal /day giving a total of approximately 44,598 gal /day in the developed Edelweiss North area. So an estimated sewer flow of 0.06901 cfs was derived from the water demand for this area. The peak flow is calculated by multiplying the flow by a factor of 4 resulting in 0.27605 cfs. This sewage flows into a 6" line on the northwest side of Rock Prairie Road, which enters an 8" line running parallel to Old Wellborn Rd. After crossing Rock Prairie Rd. another 6" line joins the 8" line carrying waste from a portion of Edelweiss South consisting of an Exxon, Sonic, and an automated car wash. The 8" line then collects waste directly from the remainder of the Edelweiss Business South area. Page 1 of 2 The Edelweiss Business South region consists of one service station, one service station / automated car wash, one fast food restaurant, one self serve car wash, a church with a day care, and approximately 20,000 sf of office space. The assumed water usages for the area are as follows: • Service station: 400 gal /day • Fast Food Restaurant: 2200 gal /day • Car Wash: 3100 gal /day • Total Office Space (20,000 sf): 5000 gal /day • Service Station / Automated Car Wash: 6700 gal /day • Church with day care: 1200 gal /day These values were calculated based on published values. The total water demand /sewage output was calculated at 18,600 gal /day in the Edelweiss Business South region. The service station, automated car wash, and fast food restaurant produces 9,300 gal /day (0.01439 cfs) of flow into a 6" line prior to entering the 8" pipe. Multiplying this by four, the result is 0.05756 cfs at peak flow. The remainder of the sewage from the Edelweiss Business South development is to be 9,300 gal /day (0.01439 cfs), which directly flows into the 8" line. The peak values of the sewage flowing through the 8" line from Edelweiss Estates North and Edelweiss Business South results in a flow of 0.39118 cfs through the 8" line. Extra Capacity: Using a nomograph, it was found that the maximum flow in the 6 "pipe and 8" pipe are respectively 0.55 cfs and 0.80 cfs. The peak flow into the 8" line from Edelweiss Estates North is 0.27395 cfs. At the tie, Williamsgate will add an additional 0.08131 cfs resulting in reserve capacity in the 8" line of 0.44474 cfs. Further down the 8" line, additional sewage from Edelweiss South area of 0.11513 cfs enters the line. Thus the net available capacity that remains in the 8" line is 0.32750 cfs. Results: The 8" line serving the total Edelweiss development area is at about half capacity at peak flows. Therefore, the addition of 0.08131 cfs (-52,500 gal /day) of sewage that the Williamsgate subdivision will create will have a minor impact on the capacity of the existing lines and will leave 0.32750 cfs remaining capacity in the 8" line. Attachments: • Map of line locations and tie in • Nomograph • Water usage references Page 2 of 2 RiverTown DRI /ADA QUESTION 17 - WATER SUPPLY See State Comprehensive Plan (Chapter 187, F.S.) GOAL (8); POLICIES (1), (5), (11) GOAL (16); POLICIES (1), (2), (6) GOAL (18); POLICIES (1), (2), (3), (4), (6) A. 1. PROVIDE A PROJECTION OF THE AVERAGE DAILY POTABLE AND NON - POTABLE WATER DEMANDS AT THE END OF EACH PHASE OF DEVELOPMENT. IF SIGNIFICANT SEASONAL DEMAND VARIATIONS WILL OCCUR, DISCUSS ANTICIPATED PEAKS AND DURATION. USE THE FORMAT BELOW: Table 17 -1, following, shows the average daily potable and non - potable water demand by phase. Total average daily potable water demand at project build out is estimated to be 1.684 million gallons per day (MGD). Total daily non - potable (irrigation) water demand is estimated to be 1.564 MGD. Daily consumption rates are based on annual averages that will vary throughout the year. Significant seasonal non - potable (irrigation) water demand may occur during drought periods. It is not anticipated that potable water demands will have significant seasonal demand variations. A. 2. DESCRIBE HOW THIS DEMAND INFORMATION WAS GENERATED, INCLUDING THE IDENTIFICATION OF THE CONSUMPTION RATES ASSUMED IN THE ANALYSIS. The following assumptions were used to estimate the demand information provided in Table 17 -1: Land Use Demand for Potable Water Single Family 350 gpd /unit Multi - Family 300 gpd /unit Retail 150 gpd /1,000 s.f. Office 150 gpd /1,000 s.f. Light Industrial 100 gpd /1,000 s.f. Golf Course 25,000 gpd Parks Buildings 200 gpd /1,000 s.f. Schools Elementary 20 gpd /student Middle 25 gpd /student Note: Potable demand rates are based on Chapter 10D -6, F.A.C. Water Supply 17.1 RiverTown DRI /ADA Land Use Demand for Non - Potable Water Single Family 180 gpd /unit (725 gpd per acre and 0.25 landscape acres per lot) *Multi- family 75 gpd /unit (5,000 gpd /acre x 15% irrigated area x 10 units /acre) *Retail 100 gpd /1,000 s.f. *Office 100 gpd /1,000 s.f. *Industrial 100 gpd /1,000 s.f. Golf Course 650,000 gpd *Parks 1,000 gpd /acre (5,000 gpd /acre x 20% irrigated area) Schools Elementary 15 gpd /student (5,000 gpd /acre x 15% irrigated x 15 acres per school /700 students per school) Middle School 22 gpd /student (5,000 gpd /acre x 15% irrigated area x 30 acres per school /1,000 students per school) *For non - residential, except golf course, demand for non - potable assumed to be 5,000 gpd per acre of irrigation area. B. PROVIDE A BREAKDOWN OF SOURCES OF WATER SUPPLY, BOTH POTABLE AND NON - POTABLE, BY DEVELOPMENT PHASE THROUGH PROJECT COMPLETION. USE THE FORMAT BELOW. Table 17 -2, following, gives the sources of the estimated potable and non - potable demand. Potable water will be supplied by the St. Joe Utility Company from off -site through a bulk supply agreement with JEA. The primary source for irrigation will be a combination of reuse water and surface water withdrawals from the on -site retention /detention ponds. Secondary sources may include shallow wells and /or Floridan Aquifer wells. The actual irrigation requirements will be determined during the final design, and the lowest available quality source of water will be selected at that time. C. IF WATER WELLS EXIST ON -SITE, LOCATE THEM ON MAP H AND SPECIFY THOSE THAT WILL CONTINUE TO BE USED. ALSO LOCATE ON MAP H ALL PROPOSED ON- SITE WELLS. (FOR RESIDENTIAL DEVELOPMENTS, IF INDIVIDUAL WELLS FOR EACH LOT ARE PROPOSED, SIMPLY INDICATE THE NUMBER OF UNITS TO BE SERVED, GENERAL LOCATIONS, AND ANY PLANS FOR EVENTUAL PHASE -OUT.) INDICATE THE DIAMETER, DEPTH, AND PUMPING RATES (AVERAGE AND MAXIMUM) FOR EACH OF THE EXISTING WELLS AND PROJECT THIS INFORMATION FOR THE PROPOSED WELLS (FOR LOTS SERVED BY INDIVIDUAL WELLS, THIS INFORMATION MAY BE GROUPED FOR PROJECTION PURPOSES). ALSO PROVIDE A BREAKDOWN OF THE WELLS WITH REGARD TO POTABLE AND NON - POTABLE SOURCES. Currently, there is only one known water well on the RiverTown property. The well is located in the northwest sector, and the location is shown on Map D. This well into the upper Floridan Aquifer was constructed in December 1989 as a test/production well with a 16 inch casing, 338 feet below land surface and a Consumptive Use Permit was issued by SJRWMD for its use as Water Supply 17.2 SANITARY SEWER ANALYSIS FOR WILLIAMS GATE SUBDIVISION 20.27 ACRE TRACT (VOLUME 4628, PAGE 221) CRAWFORD BURNETT LEAGUE, A -7 MDG JOB NO. 000886-3736 COLLEGE STATION, BRAZOS COUNTY, TEXAS JANUARY 2005 Ty,.., f 1 N a L" i S. D� MS o t.1 / � G 57 cz, , 0 M 1 2551 Texas Ave. South, Ste. A, College Station, TX 77840 cf @Q w Ofc: 979.693.5359 Fax: 979.693.4243 Email: mdgcstx @yahoo.com 0��40 Project Scope and Description: The purpose of this analysis is to determine whether there is adequate capacity in the existing sewer line to provide service for Williamsgate Subdivision. The project site is located just southwest of Old Wellborn Road along Rock Prairie Road beginning 1,059 feet southwest of Old Wellborn Road. The proposed tie to the existing system is an 8" line located northeast of Old Wellborn Road in the Edelweiss Estates /Business Area. This tie lies within the boundary of the Sanitary Sewer Area 92 -01. Analysis of Proposed Sewer Flow: Williamsgate Subdivision is classified for residential land use and consists of 20.27 acres with 82 proposed lots. Using the Land Use Determination Method of flow from the 2004 Bryan/College Station Uniform Design Guidelines, the flow for the proposed site was estimated. The peak flow was calculated by multiplying the Average Daily Flow by 4.0. The estimated flow for Williamsgate Subdivision is 21,894 gpd with a peak flow of 61 gpm. Lift Station: The proposed lift station to be used in the Williamsgate subdivision is a Duplex 4: Non - Clog Lift Station (model # - BPSRA40- 72240VBS). This model runs on two Myers 4" non -clog submersible pumps which allows a minimum of a 3" solid to pass. The wet well used for the lift station is fiberglass reinforced polyester, and, because it is a wet well, odor ventilation is reached through a vent located at the top of the well (no mechanical ventilation is required). Also, each pipe leading away from the pumps have check valves at its discharge. After basing specifications on Chapter 317.3 of the Design Criteria for Sewerage Systems, the Williamsgate Duplex 4" Non -Clog Lift Station meets the requirements. Sanitary Sewer Service Area 92 -01 Capacity: The proposed tie -in location is within the boundaries of the 92 -01 Service Area. Flow capacity data for this area was obtained from TEXCON's "Sanitary Sewer Analysis, Impact Fee Service Area 92 -01 for Dove Crossing Subdivision Phases 1" dated October 2004. This analysis evaluated the land use areas of the 92 -01 Service Area and the area served by the 18" sanitary sewer line which discharges into the lift station near State Highway 6. Four land use areas with a total area of 20.6 acres serve the 8" line at the tie -in location. These areas include retail, office, commercial, and church. The TEXCON analysis estimated the total flow from these four land use areas to be 25,259 gpd with a peak flow of 18 gpm. Using a nomograph with the minimum required slope for an 8" pipe, it was estimated that the 8" line has a capacity of 359 gpm with a velocity of 2.6 fps. The TEXCON analysis estimated that a total flow of 665,556 gpd with a peak flow of 1,849 gpm discharged from the 18" sewer line into the lift station. The analysis also determined that the 18" line has a capacity of 2213 gpm with a velocity of 3.1 fps. Results: The 8" line at the tie -in is currently at 5% capacity. The capacity including the flow from Williamsgate would be 22 %. The capacity of the 18" line is currently 70 %. With the additional flow from Williamsgate, the capacity would be 86 %. The existing sanitary sewer line has adequate capacity for the development of Williamsgate Subdivision. Attachments: • Map of line locations and service areas • Nomograph • Flow calculations