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Home My WebLink About028 WaterWastewater ENGINEERING CONSULTING PLANNING DESIGN 204 N. 11th Ave.  BOZEMAN, MT 59715  406‐581‐3319  www.g‐e‐i.net 204 N. 11th Ave., Bozeman, MT 59715 Cell: (406) 581-3319 www.g-e-i.net Page 1 of 6 Water and Wastewater Design Report Current Landing, LLC Offices Corner of Fallon and Laramie St. Lot 2, Block 1 of Parkway Plaza Subdivision Bozeman, Montana December 2022 Prepared By: Genesis Engineering, Inc. GEI Project #: 1097.003 Prepared For: Current Landing, LLC Bozeman, Montana 204 N. 11th Ave., Bozeman, MT 59715 Cell: (406) 581-3319 www.g-e-i.net Page 2 of 6 H:\1154\004\DOCS\DESIGN\WTR‐SWR\WP\WaterWastewaterDR.doc Water and Wastewater Design Report Table of Contents I. Project Background………………………………………………………………………………………………. 3 1. Introduction……………………………………………………………………………………………………………… 3 2. Soil and Groundwater………………………………………………………………………………………………. 3 3. Land Use…………………………………………………………………………………………………………………… 3 4. Design Standards……………………………………………………………………………………………………… 3 II. Sanitary Sewer System……………………………………………………………………………………. 4 1. Projected Flows…………………………………………………………………………………………………….….. 4 2. Collection System……………………………………………………………………………………………….……. 4 3. Service Connections………………………………………………………………………………………….……... 4 III. Water System……………………………………………………………………………………………….….… 5 1. Projected Usage………………………………………………………………………………………………….……. 5 2. Hydraulic Analysis …….……………………………………………………………………………………….……. NA 3. Water Distribution System ….……………………………………………………………………………….…. NA 4. Service Connections……………………………………………………………………………………………..….. 6 IV. Conclusion……………………………………………………………………………………………………..….. 6 Appendix A‐ As‐built Drawings & Calculations List of References City of Bozeman Design Standards and Specifications Policy, March 2004, and all addenda. Montana Public Works Standard Specifications (MPWSS), 6th Edition City of Bozeman Modifications to the MPWSS, March 2011, and all Addenda Montana Department of Environmental Quality (MDEQ) Design Circulars DEQ‐1 and DEQ‐2 204 N. 11th Ave., Bozeman, MT 59715 Cell: (406) 581-3319 www.g-e-i.net Page 3 of 6 H:\1154\004\DOCS\DESIGN\WTR‐SWR\WP\WaterWastewaterDR.doc I. Project Background I‐1. Introduction The Current Landing Project consists of 3 proposed office/storage buildings on an existing lot (2) within the existing Parkway Plaza Subdivision and PUD. This existing lot is shaded in green in Figure 1 below and consists of approximately 1.37 acres, more specifically located at the corner of Fallon Street and Laramie Street in Bozeman, Gallatin County, Montana. I‐2. Soils The NRCS Soil Survey identifies one major soil type on the proposed project site: Turner Loam (457A). This soil belongs to hydrologic soil group B as it is comprised primarily of loams with moderately high saturated hydraulic conductivity. I‐3. Land Use The existing land use is for business park offices as is currently proposed. The proposed storm water structures and building elevations will conform to City land use requirements and zoning as it proceeds through the COB site plan review process. I‐4. Design Standards All sanitary sewer mains, water mains, service connections, and appurtenances will be designed and constructed in accordance with the Montana Public Works Standard Specifications (MPWSS), 6th Edition; City of Bozeman Design Standards and Specifications Policy (including Addenda 1‐4), March 2004; City of Bozeman Modifications to the MPWSS, March 2011 (including Addenda); the Montana Department of Environmental Quality (MDEQ) Design Circulars DEQ‐1 and DEQ‐2, and any additional addenda thereof. The City of Bozeman will assume operation and maintenance of the wastewater and water systems and appurtenances upon construction and acceptance of the installation. II. Sanitary Sewer System II‐1. Proposed Design Flow The proposed Current Landing, LLC Office site includes 3 new office buildings on approximately 1.37 acres. Average day flows were calculated using the DEQ4 standard of 16 gpd per person. The estimated average Daily Flow from the proposed project is as follows: Average Daily Flowrate = (50 Employees + 300 Visitors/Rafters) x 13 gpd/person = 4,550 gpd Using a 350 person population, a peaking factor was calculated by the following formula, where P = population (thousands): PF = 18 + P0.5 4 + P0.5 Using peak hour factor of 4.05 and adding the City’s infiltration allowance of 150 gallons per acre per day resulted in a combined peak hourly flowrate as follows: 204 N. 11th Ave., Bozeman, MT 59715 Cell: (406) 581-3319 www.g-e-i.net Page 4 of 6 H:\1154\004\DOCS\DESIGN\WTR‐SWR\WP\WaterWastewaterDR.doc Peak Hourly Flowrate = ADF x PHF + 150 gpd/acre Peak Hourly Flowrate = 4,550 gpd x 4.05 + 150 gpd x 1.37 = 18,633 gpd Using Manning’s Equation and a minimum slope of 0.004 ft/ft for an 8‐inch diameter pipe, the full‐flow capacity of the pipe is 0.76 cfs or 497,629 gallons per day. The empirically‐based peak design flow occupies 3.77 % of the existing 8‐inch sewer main. The full flow velocity of the 8‐inch diameter SDR‐35 main is 2.2 ft/sec, exceeding the minimum of 2.0 ft/sec required. II‐2. Collection System The wastewater will be collected within the site with new 4‐inch sewer services for each building connecting to the existing 8‐inch sewer mains within Laramie Dr. and Fallon St.. No new sanitary sewer manholes or 8” sewer main is proposed with this project. II‐3. Service Connections Service connections (4‐inch) are proposed for each of the three buildings. Connections to the sanitary sewer mains will be designed in accordance with the City’s Design Standards and Specifications Policy. Connections to the sewer main will be made with in‐line gasketed wyes. III. Water System III‐1. Projected Usage The proposed Current Landing, LLC Office site includes 3 new office buildings. Using the sewage generation flows from Part II‐1 above, Genesis estimated the total average daily demand (ADD) as seen below. Using the City’s max day flow factor of 2.3, results in the maximum daily demand as shown below. Multiplying the average daily flow by the City’s peak hour factor of 3, results in a peak hour demand as shown below. Local landscape watering is included in the empirical data and thus the peaking factors. Watering of any green space will likely be completed using an irrigation well onsite. The average daily demands are exclusive of the suggested fire flow requirement of 2,000 gallons per minute. When modeled, the system satisfies the fire flow occurring simultaneously with the maximum day demands inclusive of the existing subdivision previous design reports. Average Daily Flowrate = (50 Emp. + 300 Visitors/Rafters) x 13 gpd/person = 4,550 gpd 4,550 gpd /1440 min per day = 3.16 gpm Maximum Daily Flowrate = ADF x 2.3 = 3.16 gpm x 2.3 = 7.27 gpm Peak Hour Flowrate = ADF x 3 = 3.16 gpm x 3 = 9.48 gpm III‐2. Hydraulic Analysis The hydraulic modeling program WaterCAD is used to model domestic and fire protection demands for the proposed site. The model uses hydrant flow test results as provided by the City of Bozeman. Since no new mains are proposed and the Max Day flow is only an additional 7.27 gpm, the minimum flow of 2,000 gpm required during the original subdivision approval is still adequate. Should more recent hydrant test results become available, we can quantify the exact amount for the neighborhood. The results are as follows: Available Fire Flow is > 2,000 gpm at 20 psi. Minimum System Pressure > 35 psi throughout the system. 204 N. 11th Ave., Bozeman, MT 59715 Cell: (406) 581-3319 www.g-e-i.net Page 5 of 6 H:\1154\004\DOCS\DESIGN\WTR‐SWR\WP\WaterWastewaterDR.doc III‐3. Water Distribution System No 8‐inch diameter ductile iron pipe (DIP) Class 51 water main will be installed for the proposed project. If new mains were proposed, all water mains would be designed to meet the 10‐foot horizontal and 18‐inch vertical separation requirements from all proposed sanitary and storm sewer mains. III‐4. Service Connections Future service connections to the water mains will be designed in accordance with the City’s Design Standards and Specifications Policy and sized based on the projected usage for each service line. Service lines less than 4 inches in diameter will be type “K” copper pipe, while those equal to or larger than 4 inches will be ductile iron. Water services will meet all applicable design standards and flow requirements. IV. Conclusion The analysis and calculations included in this report demonstrate that the proposed designs for water provision, including fire flow, and wastewater disposal satisfy state and local design requirements. 204 N. 11th Ave., Bozeman, MT 59715 Cell: (406) 581-3319 www.g-e-i.net Page 6 of 6 H:\1154\004\DOCS\DESIGN\WTR‐SWR\WP\WaterWastewaterDR.doc Appendix A Currrent Landing Offices Sewer Demand Calcs 204 N. 11th Avenue, Bozeman, MT 59715 These calculations are used to determine the average sanitary sewer flow and required sewer pipe diameters for the project. Using Mannings Equation, the full flow capacity of the proposed PVC sewer line is: Qfull = (1.486/n)*A*R^(2/3)*S^(1/2) where: Diameter = 8 inches n = 0.0130 for PVC A = Pi*r^2 = 0.35 ft^2 P = 2*Pi*r = 2.09 ft R = A/P = 0.1667 ft S = 0.0040 ft/ft Qfull = 0.76 CFS Estimate Proposed Peak Sewage Flow Rate for Pipe Design only Parcel USE NUMBER OF EMPS Lot Area Empirical ADF SQFT ‐ USE Acres (ADD) gal/day g/d/person OFFICE 350 1.37 13 4,550 Total Area = 1.37 Total 4,550 Equivalent Population Average Daily Flow / 89 gal/capita/day = 350 people Peaking Factor Qmax= 18 + P^(1/2) = 4.05 4.05 Qave 4 + P^(1/2) Peak Hourly Flow Rate PHF = Average Daily Flow * Peaking Factor = 18,428 gal/day Infiltration = 150 gallons/ day / acre = 206 gal/day Total PHF = 18,633 gal/day or 0.029 cfs Using the above values, velocity at peak hourly flow is: V=(1.486/n)*R^(2/3)*S^.5 = 0.08 ft/sec and Qmax = 3.77 % Qfull