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Home My WebLink About97 - Design Report - Yellowstone Peaks Mobile Home Park - Water, Sewer, Stormwater, Streets NUM FE APR 1 6 1 7, DESIGN REPORT FOR YELLOWSTONE PEAKS MOBILE HOME PARK Prepared for: DENNIS BALIAN Prepared by: C &H ENGINEERING AND SURVEYING, INC. 614 WEST LANIlVIE STREET BOZEMAN, MT 59715 (406) 587-1115 96270 FEBRUARY, 1997 INTRODUCTION The proposed Yellowstone Peaks Mobile Home Park is located on West Babcock Street approximately 1,800 feet west of the intersection of West Babcock and Main Street, in Bozeman,Montana. Currently,there is one single family dwelling with an attached garage on the site, served by private a well and septic system. The tract is part of the Fowler Subdivision and is 1,333.2 feet long in the north-south direction and varies in width from 197.6 to 218.6 feet in the east-west direction. It is the owner's desire to develop the tract into 36 "lots" under the City of Bozeman's R-MH zoning designation. This would include tying into City of Bozeman water and sewer utilities, paving West Mendenhall where it crosses the site and constructing a private road(Sunlight Avenue)up the middle of the tract. Sunlight Avenue will be constructed with curb and gutter to a width of 23 feet from back of curb to back of curb. West Mendenhall will be constructed to City of Bozeman standards, 37 feet from back of curb to back of curb. This preliminary plat application is made as a replacement for the previously approved 44 unit Yellowstone Peaks Townhouses. A Traffic study was submitted as part of that application, and the remainder of the environmental assessment and community impact report was waived due to the inclusion of that information in the master plan for the area. WATER SYSTEM Summary Current water mains and stubs in the area include a 10 inch D.I.P. that runs east-west on the south side of West Babcock, a 6 inch stub to the west of the proposed development in West Mendenhall Street (in the Westgate Subdivision), and a 6 inch stub to the northwest of the proposed development from the Greenway Subdivision. At the time of this writing, plans have been submitted for the construction of the Wheeler Mobile Home Park immediately to the west of the proposed subdivision. Approximately 1,400 feet of 6 inch D.I.P. will be run northerly from the 10 inch main on the south to the stub at the Wheeler Mobile Home Park on the north. A 6 inch diameter water main will be run in the proposed West Mendenhall Street from the stub in the proposed Wheeler Mobile Home Park to the west, to the east boundary line where it will be stubbed and capped. By connecting to the stub in the Wheeler Mobile Home Park,two loops will be created. Individual water services to each unit will connect to 1.5 inch diameter service headers with meter pits, which in turn are connected to the new 6 inch line. The existing house will connect directly to the 6 inch line, via a 3/4" service line. Design Requirements Daily Domestic Usage=350 gpd per unit Total Units=35 2 Daily Domestic Usage For All Units=(350 x 35) 12,250 gpd Peaking Factor= 3 Peaked Daily Domestic Usage For All Units=36,750 gpd=25.52 gpm Irrigation Flow=(1 inch/week) x(1/12 ft/inch) x(43560 ft2/acre)x(4 acres)x (1/7 weeks/day) x (7.48 gal/ft )= 15,516 gpd= 10.80 gpm Fire Flow= 1000 gpm Total Flow=25.52 gpm + 10.80 gpm + 1000 gpm= 1036.32 gpm Available Pressure= 125 psi Residual Pressure Required=20 psi Available Pressure For Head Loss =(125-20) 105 psi Available Head=(105 x 2.31)=242.55 ft Head Loss= 9 ft(Hazen-Williams, C=120) Head Remaining=(242.55 -9)=233.55 ft A conservative value of C= 120 was used in the Hazen-Williams equation for the ductile iron pipe. No minor losses were introduced into the analysis as the C-factor is considered conservative. Using a iterative nodal analysis, a head loss of 9 feet can be expected. Since this is less than the available head loss,the proposed system is satisfactory. WATER DISTRIBUTION SYSTEM SIZING Meters and Service Lines are sized based on the Fixture Unit method found in the Uniform Plumbing Code. (U.P.C.) Fixture Units: Kitchen sink =2 Bathtub/shower =2 Sink = 1 Toilet =3 Laundry =2 Half Bath or D/W =2 = 12 Lots 2-11 12 F.U. /unit x 10 units = 120 Total F.U.'s From Chart A-3 (U.P.C.), 120 F.U. =48 gpm 3 From Chart A-4 (U.P.C.), 48 gpm = 1.5" pipe @ 9 ft/s @ 8 psi of head loss per 100 ft of pipe . 400'/ 100' x 8 psi = 32 psi. Head loss OK, use 1.5" service line. Lots 12-22 12 F.U. /unit x 12 units = 144 Total F.U.'s From Chart A-3 (U.P.C.) 144 F.U. = 54 gpm From Chart A-4 (U.P.C.) 54 gpm = 1.5" pipe @ 10 ft/s @ 10 psi of head loss per 100 ft of pipe 400'/ 100' x 10 psi =40 psi. Head loss OK, use 1.5" service line. Lots 23-35 12 F.U. /unit x 13 units = 156 Total F.U.'s From Chart A-3 (U.P.C.) 156 F.U. = 56 gpm From Chart A-4 (U.P.C.) 56 gpm= 1.5" pipe @ 10 ft/s @ 10 psi of head loss per 100 ft of pipe 400'/ 100' x 10 psi =40 psi. Head loss OK, use 1.5" service line. SEWER SYSTEM Summary Sewer lines will run adjacent to the proposed water lines in Sunlight Avenue. The proposed sewer line will connect to the City system in only one location. A stub has been provided in the park area of the Wheeler Mobile Home Park at the north end of the proposed subdivision. A total of four new manholes will be constructed. Design Requirements Waste water flows were estimated in the following manner: Daily Flow=350 gpd per unit Total Units=35 Total Flow= (35 x 350)= 12,250 gpd= 8.51 gpm Peak Factor= (18+P")/(4+P"2) where P=population in thousands(35 units x 3 persons per unit= 105) = 4.2 Peak Total Flow=(4.2 x 8.51)35.74 gpm Waste water mains were sized in the following manner: 4 Manning's N=0.013 Minimum Slope=0.011 ft/ft Q=35.74 gpm=0.0796 cfs Percent Full (8" PVC)= 17.33 Velocity=2.02 fps Based on the previous calculations an 8" PVC sewer line at the grade shown will be more than adequate to carry the design flows. STORM WATER MANAGEMENT Summary Storm water run-off from the site will be directed by curb and gutter to a storm water retention pond located in the park area of the proposed subdivision. This retention area will filter sediment and oils from the storm runoff. The retention basin was sized for a 10 year/2 hour storm event. STORM WATER RUNOFF (PRE DEVELOPMENT) AREAS Pavement = 4578 ft2 Roofs = 1692 f12 Open land = 261,543 ft2 TOTAL = 267,813 ft2 Using Q=CiA where: Q=Flow(ft3/hr) C =Runoff coefficient =0.20 (open land) =0.60 (gravel road) =0.85 (paved road) =0.90 (roofs) i =Rain fall intensity per NOAA ATLAS =0.034 ft/hr 5 A=Area(ft2) We Have: Pavement (0.85)(0.034 fFt/hr)(4,578 ft2) = 132.3 ft3/hr Roofs (0.90)(0.034 ft/hr)(1,692 ft2) = 51.8 ft3/hr Open Land (0.20)(0.034 ft/hr)(261,543 ft2) = 1,778.5 ft3/hr TOTAL = 1,962.6 ft3/hr 244.7 gpm For a 2 hour event = 5,347.1 ft3 STORM WATER RUNOFF (POST DEVELOPMENT) AREAS Paved = 73,738 ft2 (sidewalks, driveways, road) Roofs 34x 12'x 50' = 14,400 ft Open land = 173,675 ft2 I TOTAL = 267,813 ft2 Using Q=CIA where: Q=Flow(ft3/hr) C=Runoff coefficient =0.20 (open land) =0.60(gravel road) =0.85 (paved road) =090 (roofs) i =Rain fall intensity per NOAA ATLAS =0.034 ft/hr A=Area(ft2) We have: Paved (0.85)(0.034 ft/hr)(73,738 ft2) =2,131 ft3/hr 6 ii f Roofs (0.90)(0.034 ft/hr)(20,400 ft2) =624 ft3/hr Open land (0.20)(0.034 ft/hr)(173,675 ft2) = 1,181 ft3/hr TOTAL =3,936 ft3/hr For a 2 hour event 7,872 ft3 Post Development Volume to Retain 7,872 ft3 STREETS, CURB AND GUTTER, SIDEWALKS Summary Access to the site will be provided form three points, West Mendenhall Street through the Wheeler Mobile Home Park,the Farwestern Subdivision, and West Babcock Street. West Mendenhall will be improved to City of Bozeman standards. Sunlight Avenue is a private road and will be constructed to a width of 23 feet measured from the back of curb to back of curb. Curb and gutter will be constructed to City of Bozeman standards. A 4 foot wide sidewalk on the west side of Sunlight Avenue will extend from West Babcock to the park area on the north end of the site. Street Design Requirements Both West Mendenhall and Sunlight Avenue will use the same section varying only with regard to width and sidewalk location. The surface will consist of 3 inches of asphaltic concrete over a 3 inch base of 1 inch minus crushed gravel over 9 inches of 4 inch minus select pit run. This is based on the inspection of the soils on site and sites in the immediate vicinity of the proposed construction, in addition to the previous performance of this section in similar applications. As is normally done, the topsoil will be removed, and the sub-grade material will be inspected for suitability, and compacted to 95% of maximum before placement of sub-base and base course material. Any soft clay or organic material encountered will be removed and replaced. 7