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HomeMy WebLinkAbout011 Water-Wastewater Design ReportWater/Wastewater Design Report 14th & Patrick Affordable Housing – Bozeman, MT WGM Project Number: 221213 05.26.2023 (Revised August 22, 2023) 109 E Main Ste B, Bozeman, MT 59715 I OFFICE 406.728.4611 I EMAIL wgm@wgmgroup.com WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING PREPARED FOR: Kaas Wilson Architects 1301 American Blvd E, Suite 100 Bloomington, MN 55425 PREPARED BY: Shane Strong, PE Senior Project Engineer WGM Group, Inc. Derek Dennehy, PE Project Engineer WGM Group, Inc. REPORT DATE: 05.26.2023 REVISION DATE: 08.22.2023 WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING CONTENTS 1.0 INTRODUCTION AND PROJECT DESCRIPTION .......................................................................... 1 1.1 PROJECT DESCRIPTION ........................................................................................................... 1 1.2 SITE INFORMATION ................................................................................................................... 1 1.3 ALTERNATE PLANS................................................................................................................... 1 2.0 WASTEWATER DESIGN ................................................................................................................ 2 2.1 FLOW DATA AND DESIGN......................................................................................................... 2 2.2 IMPACT ON EXISTING WASTEWATER FACILITIES ................................................................. 3 3.0 WATER DESIGN ............................................................................................................................. 4 3.1 FLOW DATA AND DESIGN......................................................................................................... 4 1 WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING 1.0 INTRODUCTION AND PROJECT DESCRIPTION 1.1 PROJECT DESCRIPTION The proposed development, referred to as ‘14th & Patrick Affordable Housing’, consists of a 155-unit affordable housing apartment complex. The subject property is located between Patrick Street and Tschache Lane, just south of Interstate 90 in Bozeman, MT. The subject property is located within the approved Preliminary Plat of PT Land Subdivision, Phase II on a “remainder” lot that requires further subdivision. A new lot will be created upon completion of final plat approval, which is currently under review at the City of Bozeman. A subdivision exemption was used for the proposed development. Once approved, the proposed site will be located on Lot 1, Block 2 of the Amended Plat of PT Land Subdivision, Phase II. The project will consist of a single, five-story apartment building along with an on-site parking lot, open space and site amenities to accommodate the residential use. Existing City of Bozeman water and sewer mains will be utilized to serve the development. A new 8” sanitary sewer service will be extended from the existing main in N. 14 Ave. to serve the apartment building. An existing 8” water main is stubbed out onto the subject property which will be connected and extended onto the developed lot to serve a new fire hydrant along with a 6” domestic water service and an 8” fire service to provide those respective water services to the building. Construction will begin immediately upon City of Bozeman Approval and is expected to last approximately 10 to12 months. Refer to Figure 1.1 for a depiction of the parcel location. The project will be constructed according to the Montana Public Works Standard Specifications (MPWSS), with amendments, along with Bozeman Design Standards & Specifications and Bozeman Modifications to MPWSS. 2 WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING FIGURE 1.1: VICINITY MAP WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING PROJECT CONTACT INFORMATION Primary Owner Contact Person and Phone Number Reuter Walton Development 4450 Excelsior Boulevard 400, St. Louis Park, MN 55416 Paul Keenan, VP of Development 612-282-1977 Primary Engineer Contact Person and Phone Number WGM Group 109 E Main Ste B, Bozeman, MT 59715 Shane Strong, PE – Senior Project Engineer 406-728-4611 1.2 SITE INFORMATION The project site is generally flat, with zero to two percent slopes along most of the site. Allied Engineering was hired to complete a geotechnical report in April 2022. Based on this report, the general soil profile consists of four to eight feet of very soft, very moist to wet, fine-grain silt/clay overlying medium dense to very dense alluvial gravels. Groundwater was measured at depths ranging from five to seven and a half feet below existing ground surface. According to the preliminary geologic map prepared by Lonn and English in 2002 for the eastern part of the Gallatin Valley, the project site is underlain by Quaternary-aged alluvium of braid plains deposits (Qabo). Based on previous geotechnical experience, the soil stratigraphy in this general area of Bozeman usually consists of topsoil overlying a mantling of silt, clay, and/or sand, which in turn overlies alluvial sands and gravels. Consolidated beds of tertiary-aged gravels, sands, silts, and clays underlie the Quaternary gravel deposits throughout the Bozeman area. The subject property does not lie within designated floodplain. 1.3 ALTERNATE PLANS No alternate plans have been considered as part of this project, as the proposed development lies within Bozeman city limits and will therefore connect to municipal water & sewer. WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING 2.0 WASTEWATER DESIGN 2.1 FLOW DATA AND DESIGN The new wastewater generation for the project was based upon the total population to be served by the new main and services. Population for each dwelling unit is based on the number of bedrooms per unit (i.e. number of bedrooms = number of people). The following assumptions and calculations were made per City of Bozeman Design Standard and Specifications Policy (DSSP), including an assumed infiltration rate which is added to both the calculated average daily and peak flow rates. 𝑃𝑒𝑎𝑘𝑖𝑛𝑔 𝐹𝑎𝑐𝑡𝑜𝑟 = 18 +√𝑃 4 +√𝑃 𝑤ℎ𝑒𝑟𝑒: 𝑃 = 𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑖𝑛 𝑇ℎ𝑜𝑢𝑠𝑎𝑛𝑑𝑠 TABLE 1: PEAKING FACTOR BASED ON HARMON’S FORMULA PEAKING FACTOR CALCULATION Total # of Dwelling Units (DU) 155 DU # 1-Bedroom Units 67 DU # 2-Bedroom Units 43 DU # 3-Bedroom Units 45 DU Population 288 people Peaking Factor 4.09 *Based on City of Bozeman Design Standards and Specifications Policy 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐷𝑎𝑖𝑙𝑦 𝐹𝑙𝑜𝑤 =(𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑋 𝑊𝑎𝑠𝑡𝑒𝑤𝑎𝑡𝑒𝑟 𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 𝑅𝑎𝑡𝑒) 𝑃𝑒𝑎𝑘 𝐻𝑜𝑢𝑟𝑙𝑦 𝐹𝑙𝑜𝑤(𝑃𝐻𝐹)= 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐷𝑎𝑖𝑙𝑦 𝐹𝑙𝑜𝑤 𝑋 𝑃𝐹 TABLE 2: WASTEWATER DEMAND CALCULATION WASTEWATER DEMAND CALCULATION Lot Area 3.26 acres Assumed Infiltration Rate* 150 gallons/acre/day Infiltration Rate 489 gpd Wastewater Generation Rate* 89 gallons/day/person Average Wastewater Flow Rate 18.14 gpm Peak Wastewater Flow Rate 73.14 gpm *Based on City of Bozeman Design Standards and Specifications Policy The minimum eight-inch piping will be used for the sewer main extension to serve the development. Laid at a minimum slope of 0.4 percent, eight-inch piping with a Manning’s coefficient of 0.013 at 75 percent full, has a capacity of 0.65 cubic feet per second (cfs), or 291 gallons per minute (gpm). WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING Therefore, the proposed pipe size is more than adequate to convey the anticipated 73.14 gpm of peak wastewater flow rate. 2.2 IMPACT ON EXISTING WASTEWATER FACILITIES The existing eight-inch SDR 35 PVC sewer main in N. 14th Avenue is sloped at 0.75 percent. At 75 percent full, its maximum capacity is 0.93 cfs, or 417 gpm. Referencing the City of Bozeman Wastewater Capacity viewer (see Figure 2 below), the existing sewer main in 14th Ave. is less than 50% obligated. If the worst-case scenario were assumed and the existing main is at 50% capacity, the sewer main would have a peak flow of 229 gpm. This liberally assumes that the “less than 50% obligated” is referring to the entire pipe diameter, not the 75% maximum set by the City of Bozeman Design and Specifications Policy. If the “less than 50% obligated” is referring to the 75% pipe full maximum, there would be more capacity in the pipe than what WGM Group has assumed. By adding the calculated 73.14 gpm proposed peak flow from Section 2.1 of this report to the current reported “less than 50% obligated” maximum flow of 229 gpm, the proposed development would theoretically increase the peak flow in the existing main to 302 gpm which is 115 gpm (28%) less than the design “75% full” capacity of the existing main. The calculated increase in pipe flow still puts the total pipe flow well below the capacity of the existing main. Refer to Figure 2 below for a visual of the criticality state of the existing main(s). Based on this analysis, no significant impact on the system will result from this proposed sewer main extension project. FIGURE 2: BOZEMAN GIS WASTEWATER CAPACITY WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING 3.0 WATER DESIGN 3.1 FLOW DATA AND DESIGN An average daily demand of 170 gallons per capita per day unit has been used per City of Bozeman Design Standards and Specifications Policy for domestic water demand. Demand data has been calculated in accordance with the City of Bozeman Design Standards. TABLE 3: PROJECTED WATER DEMAND WATER DEMAND # of Dwelling Units 155 DU # 1-Bedroom Units 67 DU # 2-Bedroom Units 43 DU # 3-Bedroom Units 45 DU Population 288 people Avg. Daily Use* 170 gpd/person Avg. Day Demand (ADD) 34 gpm Maximum Day Demand (ADD x 2.3)* 78.2 gpm Peak Hour Demand (ADD x 3)* 102 gpm *Based on City of Bozeman Design Standards and Specifications Policy The proposed water service has been sized at 6” by the building’s MEP consultant for the domestic service line. Per City of Bozeman DSSP, the velocity in a service line should not exceed 10 feet per second. Based on the peak hour demand calculated in Table 3 above at 102 gpm, a 6” service would have a velocity of 1.16 feet per second, which satisifies the City of Bozeman DSSP reqirement. The fire service line has been sized by the building’s MEP consultant as 8”. The building’s sprinkler system consultant has designed the fire sprinkler system with a demand of 1,000 GPM. Based on this system’s flow, an 8” fire servcie would have a velocity of approximately 6.40 feet per second, which satisfies the City’s DSSP requirement. Fire flow data was requested for the existing main proposed for connection. The Bozeman water department provided the hydrant flow test. The test resulted in a hydrant flow of 1,300 gpm at the mid- block hydrant on N. 14th Ave. with a static and residual pressure of 80 psi at the hydrant located at the intersection of Tschache and N. 14th (Appendix A). Given the system pressure drop of zero psi during the hydrant flow test, the looped main surrounding the site with multiple fire hydrants will more than exceed the required fire flow requirements of fire flow demand plus maximum day demand (1,500 gpm + 78.2 gpm = 1,578.2 gpm). Additionally, a combined building demand for sprinkler system and maximum day demand (1,000 gpm + 78.2 gpm = 1,078.2 gpm) would result in a pressure drop of less than 2 psi along the 8” water main extension from the connection point to the service connections. WGM recommends the City confirm available fire flows for its localized water system within the approved subdivision with its current water system model. WATER/WASTEWATER DESIGN REPORT 14TH & PATRICK AFFORDABLE HOUSING APPENDIX A CITY OF BOZEMAN Fire Flow Request Form PHONE (406) 582-3200 FAX (406) 582-3201 The results of the fire flow information that you requested are as follows North 14th ave HD #439 Static – 80PSI, Residual – 80PSI HD#2352 Pitot –60PSI flowing 1300 GPM on a 2.5” nozzle. Fire Flow test performed on 6/2/2023. If you have questions or need further information feel free to email. Data Disclaimer: Water distribution information is calculated using hydraulic modeling software and is subject to variation. Actual field conditions may vary. This information provided to the requestor for evaluation purposes only, without warranty of any kind, including, but not limited to any expressed or implied warranty arising by contract, stature, or law. In no event regardless of cause, shall the City be liable for any direct, indirect, special, punitive or consequential damages of any kind whether such damages arise under contract, tort, strict liability or inequity.