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Home My WebLink About01 - Design Report - Annie Ph III WATER, SEWER & STREET IMPROVEMENTS DESIGN REPORT for ANNIE SUBDIVISION PHASE III BOZEMAN, MONTANA May, 2001 W.O. # 96-644 s S ENGINEERS REPORT Revised 7/17/01 1. INTRODUCTION: Gaston Engineering and Surveying has been retained by Roger Smith to design water, sewer, and streets for phase III of Annie Subdivision. The minium pipe sizes of 8" for water and sewer mains has been used for this project. The proposed density does not exceed the minimum pipe size. 2. FIRE FLOW REQUIREMENTS: Adequate fire flow can be achieved in a 8"water main. There are six fire hydrants proposed for this project. The Uniform Fire Code states that fire flows for one and two family dwellings having a fire area that does not exceed 3600 sf shall be 1,000 gpm. City of Bozeman Fire Marshall reportedly requires 1,500 gpm fire flow. Line sizes of 8" dia are capable of this capacity. 3. WATER USE: Water use for projects such as this are small in comparison to required fire flows. For design purposes, we have estimated 73 living units at an average population of 2.5 people per household. Domestic demand is based upon 2.5 people per unit times 100 gpd per person. Irrigation demand is estimated by applying 1.5" per week on an average landscape area of 5,000 square feet. Domestic 73 x 2.5 people/unit = 182.5 people 182.5 people x 100 gpd/person = 18,250 gpd Irrigation 73 units x 5,000 sf = 365,000 sf 365,000 sf x 1.5"/wk — 45,625 cf 45,625 cf/wk_ 7 days/wk = 6,518 cf/day 6,518cf/day x 7.48 gal/sf = 48,754 gpd Irrigation = 48,754 gpd Domestic = 18,250 gpd Daily demand = 67,000 gpd The maximum daily demand is therefore 67,000 gpd= 1440 min/day or 46.5 gpm. Total maximum daily demand with fire protection is 1,550 gpm. A hydraulic analysis is attached which demonstrates that the proposed 8" main can provide 1,550 gpm. 3. SEWER MAIN SIZE: Sewer demand is the same as the domestic demand estimated above. The daily demand is 18,250 gpd_ 1440 min/day or 12.7 gpm. Peak demand assuming a peak factor of 4 would be 50.7 gpm or 0.113 cfs. A 8" sewer main proposed at 0.4% grade or steeper which will have a capacity of 0.53 cfs at 2/3 full flow. The resulting velocity of this flow would be 2 ft/sec. 4. PLANS & SPECIFICATIONS: The plans & specifications for this project will accompany this report and will include the infonnation required in the "Plans & Specifications" of Chapter 1 in MT Department of Health & Environmental Sciences" Circular WQB 1 and WQB 2. ► Location, size, scope, depth, materials and installation procedures of constructing water and sewer mains. ► Location of fittings, valves, hydrants, ect. ► Location of proposed and existing utilities in the area of the proposed development and land adjacent to it. ► Lot boundaries. 5. STORM DRAINAGE CALCULATION: The storm drainage boundary consists of approximately 11.07 acres and is shown on enclosed exhibit. Storm water runoff will drain to the north side of Roger's Way and be collected by a catch basin. Collected runoff will then flow through storm drainage pipe to the proposed detention pond. The proposed detention pond will detain runoff to the pre-developed discharge rate of a 10 year storm event. A discharge structure at the outlet of the detention pond will utilize a weir to control discharge at the pre-developed rate. The required basin size is 5,220 cf with a 1.6 cfs discharge controlled by a weir that is 4.5 in wide by 1.25 ft high. 6. STREET PAVEMENT SECTION: We have designed the proposed pavement section according to ASSHTO Pavement Section Design Requirements. We have selected a subgrade modulus which is conserve. R-value testing of the inorganic silty clay soils on this project site have been reported at less than 5. The resulting modulus is 3.5 ksi. We feel that with the construction of water and sewer mains beneath the proposed street the subgrade strength of the backfill material will be higher than native silty clay. We are proposing a pavement section as follows: Asphalt 3" Base 12" Total 15". The minimum required structural number is 2.8. A 15" section as described above equals 2.8 based upon the following parameters: • 20 year design life. • The estimated future traffic of travel lane = 50,000 EAL • The standardized normal deviate =-1.04 • The overall standard deviation =0.45 • Resilient modulus of subgrade = 3.5 • Initial serviceability =4 0 Tenninal serviceability =2.5 tmp#4.txt Weir Calculator Given Input Data: Weir Type . . . . . . . . . . . . . . . . . . . . . . . Rectangular Equation Contracted Solving for width Flowrate . 1.6160 cfs Depth of Flow 15.0000 in Coefficient 0.6500 Height . . . . . . . . . . . . . . . . . . . . . . . . . . 15.0000 in Computed Results: Full Flow 1.6160 cfs velocity 2.2188 fps width . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9918 in Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7283 ft2 Perimeter . . . . . . . . . . . . . . . . . . . . . . . 36.9918 in wet Perimeter . . . . . . . . . . . . . . . . . . . 36.9918 in wet Area . . . . . . . . . . . . . . . . . . . . 0.7283 ft2 Percent Full . . . . . . . . . . . . . . . . . . . . 100.0000 Page 1 Rectangular Weir Formulas You can use the Rectangular Weir Calculator to calculate hydraulic values for suppressed and contracted rectangular weirs. The following formula is used to calculate the design flow rate for a suppressed weir. Q=TCL 2g(H)1.5 The following formula is used to calculate the design flow rate for a contracted weir,including a correction(-0.2m to the effective length to account for edge contractions. Q=3 c(L—0.2H) 2g(H)1s where: Q=Design flow rate c=Weir coefficient L=Length of weir g=Acceleration due to gravity(32.174 ft/s2 or 9.807 m/s2) H=Weir head STORM DRAINAGE CALCULATIONS DETENTION POND 10 YR. STORM ANNIE SUBDIVISION PHASE M GROSS AREA 11.074 ACRES 482324.000 FT A 2 PROPOSED IMPROVED AREA = 93000.000 FT A 2 STREETS & R/W 93000.000 FT A 2 0.000 FT A 2 0.000 FT A 2 RESIDENTIAL LOT AREA = 389324.000 FT A 2 COEFFICIENT OF RUNOFF C UNIMPROVED = 0.300 IMPROVED = 0.850 COMBINED = 0.406 TIME OF CONCENTRATION RELIEF = 7.950 FT LENGTH = 885.000 FT SLOPE = 0.898 % UNIMPROVED Tc = 49.054 IMPROVED Tc = 13.626 INTENSITY & FLOW AT Tc: (1) UNIMPROVED: 1 = 0.730 IN/HR Q =CIA= 1.616 CFS DESIGN DISCHARGE IMPROVED: I = 1.677 IN/HR 25 YR INTENSITY = 2.014 Q =CIA= 3.044 CFS 25 YR RUNOFF = 3.655 DETENTION POND SIZING: A. MINIMUM VOLUME STORM INTENSITY FUTURE RUNOFF RELEASE REQUIRED DURATION RUNOFF VOLUME VOLUME STORAGE (MIN) (IN/HR) (CFS) (FT A 3) (FT A 3) (FT A 3) 25.000 1.131 5.083 7624.968 2423.338 5201.631 30.000 1.004 4.515 8127.397 2908.005 5219.392 28.000 1.050 4.722 7933.491 2714.138 5219.353 27.000 1.075 4.835 7833.148 2617.205 5215.944 26.000 1.102 4.955 7730.360 2520.271 5210.089 MAX STORAGE = 5219.392 Manning Pipe Calculator Given Input Data: shape . . . . . . . . . . . . . . . . . . . . . . . . Circular solving for . . . . . . . . . . . . . . . . . . . . . Depth of Flow Diameter . . . . . . . . . . . . . . . . . . . . . . . . 15.0000 in Flowrate . . . . . . . . . . . . . . . . . . . . . . . . 3.6550 cfs slope . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.0028 ft/ft Manning's n . . . . . . . . . . . . . . . . . . . . . 0.0130 Computed Results: Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.6180 in Area . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2272 ft2 wetted Area . . . . . . . . . . . . . . . . . . . . . 1.1706 ft2 wetted Perimeter . . . . . . . . . . . . . . . . 37.8719 in Perimeter . . . . . . . . . . . . . . . . . . . . . . . 47.1239 in Velocity . . . 3.1224 fps Hydraulic Radius . . . . . . . . . . . . . . . . 4.4508 in Percent Full . . . . . . . . . . . . . . . . . . . . 90.7867 Full flow Flowrate . . . . . . . . . . . . . . 3.4182 cfs Full flow velocity . . . . . . . . . . . . . . 2.7854 fps Critical Information Critical depth . . . . . . . . . . . . . . . . . . 9.3244 in critical slope . . . . . . . . . . . . . . . . . . 0.0063 ft ft Critical velocity . . . . . . . . . . . . . . . 4. 5481 fps critical area . . . . . . . . . . . . . . . . . . . 0.8036 ft2 Critical perimeter . . . . . . . . . . . . . . 27.2108 in critical hydraulic radius . . . . . . . 4.2529 in Critical top width . . . . . . . . . . . . . . 15.0000 in specific energy . . . . . . . . . . . . . . . . . 1.1900 ft Minimum energy . . . . . . . . . . . . . . . . . . 1.1656 ft Froude number . . . . . . . . . . . . . . . . . . . 0.6171 Flow condition . . . . . . . . . . . . . . . . . . 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