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Home My WebLink About18 - Design Report - Catron Crossing - Sewer CATRON CROSSING SUBDIVISION SEWER IMPROVEMENTS SANITARY SEWER EXTENSION BASIS OF DESIGN REPORT August, 2018 PREPARED BY: ■ Morrison Maierle engineers • surveyors • planners • scientists MMI #: 2605.025 Table of Contents INTRODUCTION...........................................................................................................................................1 1 PROBLEM DEFINED............................................................................................................................1 2 DESIGN CONDITIONS.........................................................................................................................1 3 IMPACT ON EXISTING WASTEWATER FACILITIES ........................................................................5 4 PROJECT DESCRIPTION....................................................................................................................5 5 DESIGN CRITERIA...............................................................................................................................5 6 SITE INFORMATION............................................................................................................................6 7 ENVIRONMENTAL IMPACTS..............................................................................................................6 8 OPERATION AND MAINTENANCE.....................................................................................................6 APPENDICES None Prepared-by: Morrison-Maierle, Inc. 2880 Technology Blvd. W. Bozeman, Montana 59771 Phone: (406) 587-0721 Fax: (406) 922-6702 Written By: DDK Checked By: MEE Approved By: _ MEE PROJECT NO.: 2605.025 INTRODUCTION This design report provides the criteria used as a basis of design for the Catron Crossing Subdivision sewer main extension improvements project and is submitted in conjunction with the completed plans and specifications. This report is organized following the outline recommended in DEQ-2, Section 32. This project involves the installation of approximately 778 feet of a new 8-inch sewer main extensions, and approximately five sewer manholes for the remaining development(zoned B-2) at the Catron Crossing Subdivision (for Lots 2, 3, 4, 5, 8, 9 and 10) located off of Catamount Street of the portion of the property contained in C.O.S. 1827A. Lot 1 will be served by a future sewer main to the north that will eventually drain to the proposed Davis Lift Station (CIP#WWIF24). This project is located within the City of Bozeman, Montana. See the vicinity map for location details. 1 PROBLEM DEFINED Future Commercial development is planned for the remaining lots within the Catron Crossing Subdivision. The project is proposing two 8-inch mains to convey sewer from the proposed development. This development will connect to the existing 27-inch sewer main that bisects the property to be extended for Lots 2, 3, 4, 5, 8, 9 and 10. Lot 1 will be served by a future sewer connection to the north. Comfort Suites on Lot 7 and Taco Bell on Lot 6 is already being served by existing sewer mains and services (constructed as part of EQ#13-1091). Sewer facilities included in this project will be designed in accordance with Montana Department of Environmental Quality (MDEQ) regulations. Adequate capacity will be provided to allow for growth in areas adjacent to the actual project areas. Flow and population data for the project will be consistent with the City's approved Facilities Plan, where applicable. 2 DESIGN CONDITIONS The sewer main extensions for the Catron Crossing Subdivision which is zoned B-2 (community business) per the City of Bozeman's zoning map. The capacity requirement for the sewer main extension is calculated as follows: 1 Future Construction in Lot 1 Flows connection to a proposed 8-inch sewer main: Assumptions: • COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY (Table V-1 Wastewater Flow Rate for Zoned Undeveloped Areas), Design Standards and Specification Policy, City of Bozeman) • Lot 1 Site = 1.04 ACRES • Sewer Flow Rate = 33.8 Gallons per Capita per Day (Table 2-11 Bozeman Wastewater Collection Facilities Plan Update) Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(1.04 ACRES) Wastewater Flow Rate = 2,080 gpd 33.8 Gallons per Capita per Day Population = (2,080 gpd)/(33.8 gallons per Capita per Day) = 62 people Peaking Factor(PF) _ (18+(population/1000)^.5)/(4+(population/1000)".5) Peaking Factor= 4.29 Peak-Flow=-2,080-gpd-(avg daily flow) x 4.29 = 8,902 gpd Peak Flow= 8,902 gpd = 6.18 gpm Infiltration at Lot 1 = 150 gpd per Acre = 150 gpd x 1.04 acres = 154.5 gpd Infiltration = 154.5 gpd = 0.11 gpm Total Lot 1 flow = 6.18 gpm + 0.11 gpm = 6.29 gpm Future Construction in Lot 2 and 3 Flows connection to a proposed 8-inch sewer main: Assumptions: COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY Lot 2 and 3 Sites = 4.40 ACRES Wastewater Flow-Rate = (2-1000 GAL./ACRE/DAY)(4.40 ACRES) Wastewater Flow Rate = 8,800 gpd 33.8 Gallons per Capita per Day Population = (8,800 gpd)/(33.8 gallons per Capita per Day) = 260 people 2 Peaking Factor(PF) _ (18+(population/1000)^.5)/(4+(population/1000)".5) Peaking Factor= 4.10 Peak Flow = 8,800 gpd (avg daily flow) x 4.10 = 36,080 gpd Peak Flow = 36,080 gpd = 25.06 gpm Infiltration at Lot 2 and 3 = 150 gpd per Acre = 150 gpd x 4.40 acres = 660.0 gpd Infiltration = 660.0 gpd = 0.46 gpm Total Lot 2 and 3 flow = 25.06 gpm + 0.46 gpm = 25.52 gpm Future Construction in Lot 8 Flows connection to an existing 8-inch sewer main: Assumptions: COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY Lot 8 Site = 2.84 ACRES Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(2.84 ACRES) Wastewater Flow Rate = 5,680 gpd 33.8 Gallons per Capita per Day Population = (5,680 gpd)/(33.8 gallons per Capita per Day) = 168 people Peaking Factor(PF) _ (18+(population/1000)".5)/(4+(population/1000)^.5) Peaking Factor= 4.17 Peak Flow = 5,680 gpd (avg daily flow) x 4.17 = 23,686 gpd Peak Flow = 23,686 gpd = 16.45 gpm Infiltration at Lot 8 = 150 gpd per Acre = 150 gpd x 2.84 acres = 426.0 gpd Infiltration = 426.0 gpd = 0.30 gpm Total Lot 8 flow = 16.45 gpm + 0.30 gpm = 16.75 gpm Future Construction in Lots 4, 5, and 9 Flows connection to a proposed 8-inch sewer main: 3 Assumptions: COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY Lot 4, 5, and 9 Site = 6.08 ACRES Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(6.08 ACRES) Wastewater Flow Rate = 12,160 gpd 33.8 Gallons per Capita per Day Population = (12,160 gpd)/(33.8 gallons per Capita per Day) = 360 people Peaking Factor(PF) _ (18+(population/1000)11.5)/(4+(population/1000)^.5) Peaking Factor= 4.04 Peak Flow = 12,160 gpd (avg daily flow)x 4.04 =49,126 gpd Peak Flow = 49,126 gpd = 34.12 gpm Infiltration at Lot 4, 5, and 9 = 150 gpd per Acre = 150 gpd x 6.08 acres = 912.0 gpd Infiltration = 912.0 gpd = 0.63 gpm Total Lot 4, 5, and 9 flow = 34.12 gpm + 0.63 gpm = 34.75 gpm Future Construction in Lot 10 Flows connection to an existing 27-inch sewer main: Assumptions: COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY Lot 10 Site = 1.49 ACRES Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(1.49 ACRES) Wastewater Flow Rate = 2,980 gpd 33.8 Gallons per Capita per Day Population = (2,980 gpd)/(33.8 gallons per Capita per Day) = 88 people Peaking Factor(PF) _ (18+(population/1000)11.5)/(4+(population/1000)^.5) Peaking Factor= 4.26 Peak Flow = 2,980 gpd (avg daily flow) x 4.26 = 12,695 gpd 4 Peak Flow = 12,695 gpd = 8.82 gpm Infiltration at Lot 10 = 150 gpd per Acre = 150 gpd x 1.49 acres = 223.5 gpd Infiltration = 223.5 gpd = 0.16 gpm Total Lot 10 flow = 8.82 gpm + 0.16 gpm = 8.98 gpm Please refer to the table below for comparisons between maximum flows and proposed flows and see that that proposed piping is adequate. MAXIMUM FLOW FOR PROPOSED PEAK FLOW CONVEYANCE LOT ( pm) PROPOSED CONVEYANCE m 1 6.29 Future 8-inch sewer main 346 2 &3 25.52 Proposed 8-inch sewer main 520 8 16.75 Existing 8-inch sewer main 346 4, 5&9 34.75 Proposed 8-inch sewer main 346 10 8.98 Existing 27-inch sewer main 3,599 *8-inch pipe at minimum grade (0.4%)with a roughness coefficient(n)value of 0.013 *27-inch pipe at minimum grade(0.067%)with a roughness coefficient(n)value of 0.013 3 IMPACT ON EXISTING WASTEWATER FACILITIES The existing sewer mains in the vicinity of this project can handle the increase in flows. 4 PROJECT DESCRIPTION The sewer main extensions for the Catron Crossing Subdivision will include the construction of approximately 778 feet of 8-inch SDR 35 PVC sanitary sewer main and approximately five 48" diameter manholes to serve the proposed Catron Crossing Subdivision and surrounding area. The average sewer depth is approximately 10-feet. 5 DESIGN CRITERIA Design criteria including average and peak flows as well as sewer depth information were provided in previous sections. The proposed sewer mains conform to the State's minimum vertical and horizontal separation criteria from water mains. 5 The proposed conventional gravity sewer collection system is to be constructed to City of Bozeman and the 6th Edition of Montana Public Works (MPW) standard specifications. In particular, the sewer mains shall be 8-inch diameter SDR 35 Polyvinyl Chloride (PVC) pipe. All manholes shall be standard concrete manholes spaced no more than 400 feet apart. 6 SITE INFORMATION The project site has been zoned B-2 by the City of Bozeman. The existing site is bound by Catamount Street to the South and East Valley Center Road to the North-East and an undeveloped field to the West. The site has existing grades of less than 4% and Turner loam soil deposits. 7 ENVIRONMENTAL IMPACTS There are no expected environmental impacts from this sewer main extension, as the City of Bozeman Wastewater Treatment Plant has more than adequate capacity for this extension. 8 OPERATION AND MAINTENANCE These sewer lines will be owned, operated, and maintained by the City of Bozeman. N:\2605\025\Design Docs\Reports\Water&Sewer Design Report 052317\Catron Sewer Extension Eng Report FINAL 061318.doc 6