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HomeMy WebLinkAbout19373 Additional files DESIGN REPORT STORMWATER MANAGEMENT THE NEST P.U.D. SUBDIVISION Prepared for: Center Arrow Partners, LLC P.O. Box #1633, Bozeman, Montana 59771 Prepared by: C&H Engineering and Surveying, Inc. 1091 Stoneridge Drive, Bozeman, MT 59718 (406) 587-1115 Project Number: 180805 October 2019 Page 1 of 21 INTRODUCTION The proposed Nest PUD Subdivision is a 44-lot townhome and condominium development located on a 5.41-acre parcel in Section 4, Township 2 South, Range 5 East of P.M.M., Gallatin County, City of Bozeman. A combination of site grading, curb and gutter, storm inlets, piping, and swales will be used to manage stormwater runoff on the site. Supporting stormwater calculations are attached to this report. A Drainage Area Map is included in Appendix A. Calculations for each individual drainage area (total area, weighted C factor, and time of concentration) are included in Appendix B. RETENTION/DETENTION POND DESIGN All ponds have been sized according to City of Bozeman Design Standards. They are designed with an effective water depth of 1.5 feet, and maximum side slope of 4:1. Detention ponds are sized to limit discharge to pre-development rates for the 10-year storm event. Detention ponds are also sized to retain the first 0.5 inches of rain from a 10-year, 2-hour storm event before the outlet structure begins to discharge. Calculations used for sizing each pond can be found in Appendix C. Design pond capacities were calculated using volume surfaces in AutoCAD Civil3D. STORM SEWER FACILITIES DESIGN Storm sewer facilities were sized for the 25-yr storm using Manning’s Equation. For each inlet, the contributing area, weighted C factor, and time of concentration were calculated. These values were input into Manning’s Equation to check capacity and flow characteristics for inlets, storm drain pipes, and curb gutters. All curbs are designed to maintain 0.15’ freeboard per C.O.B. Design Manual Section IV.C.5. For the purposes of this report, each pipe section was named to match the associated upstream structure. Pipe sizing calculations are included in Appendix D. Existing Retention Pond #1 Existing Retention Pond #1 is located north of Durston Road along the southern property line Lot 4. This pond will be relocated with the proposed development and will be upgraded to a detention pond in order to reduce the required footprint. The pre-development time to concentration was calculated to be 9.3 minutes and the pre-development runoff rate for the 10-yr storm was calculated Page 2 of 21 to be 0.51 cfs. There is a 1” weir in the outlet structure that limits runoff to the pre-development runoff rate of 0.51 cfs. The weir is to be located 1’ above the bottom of pond so that the first 0.5 inches of rain is retained before the stormwater is discharged into the existing wetland area. It receives runoff from Durston Road (Drainage Area #EX1). The new required pond volume was calculated to be 1,167 cubic feet from Drainage Area #EX1, totaling 1.20 acres. The proposed pond volume is 2,014 cubic feet. In the case of larger storms beyond the pond’s capacity to capture and infiltrate, the pond will overtop and flow west into Baxter Creek. Supporting calculations for the required pond volume can be found in Appendix C. Existing Retention Pond #2 Existing Retention Pond #2 is located south of Annie Street and west of proposed Lot 4. It receives runoff from Drainage Areas 1 and EX2, totaling 6.22 acres. The existing retention pond will be upgraded to a detention pond by installing an outlet structure in order to reduce the required footprint of the pond. The pre-development time to concentration was calculated to be 52 minutes and the pre-development runoff rate for the 10-yr storm was calculated to be 0.87 cfs. There is a 1.7” weir in the outlet structure that limits runoff to the pre-development runoff rate of 0.87 cfs. The weir is to be located 1’ above the bottom of pond so that the first 0.5 inches of rain is retained before the stormwater is discharged into the existing wetland area. The pond currently receives runoff from Annie Street (Drainage Area #EX2). The existing pond volume is 6,445 cubic feet at an effective water depth of 1.5’. The water depth has the ability to exceed 1.5’ as it is currently a 2.5’ deep pond. There is an existing chain link fence installed around the pond to provide a safety barrier to pedestrians. The existing required pond volume is 2,669 cubic feet (retention) from the Westbrook Subdivision and the new required pond volume including the Nest development was calculated to be 6,151 cubic feet (detention) from Drainage Areas #1 and #EX2, totaling 6.22 acres. In the case of larger storms beyond the pond’s capacity to capture and infiltrate, the pond will overtop and flow west into Baxter Creek. Supporting calculations for the required pond volume can be found in Appendix C. Page 3 of 21 APPENDIX A DRAINAGE AREA MAP Page 4 of 21 Page 5 of 21 APPENDIX B DRAINAGE AREA CALCULATIONS Page 6 of 21 DRAINAGE AREA #1 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Hardscape 0.95 126546 120219 Landscape 0.2 109161 21832 Total 235707 142051 A = Area (acres)5.4111 C = Weighted C Factor 0.60 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.3% Return (yrs)Cf C = Rational Method Runoff Coefficient 0.35 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)139 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)14.4 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft)0.13 (0.15' below top of curb) S = slope (%)0.72% L = length of gutter (ft)1000 V = mean velocity (ft/s)2.54 Tc Gutter Flow (minutes) =6.6 Tc Total =21.0 (5 minute minimum) Page 7 of 21 DRAINAGE AREA #EX1 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Hardscape 0.95 52151 49544 Landscape 0.2 0 0 Total 52151 49544 A = Area (acres)1.1972 C = Weighted C Factor 0.95 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.0% Return (yrs)Cf C = Rational Method Runoff Coefficient 0.35 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)15 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)5.2 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft)0.13 (0.15' below top of curb) S = slope (%)0.65% L = length of gutter (ft)600 V = mean velocity (ft/s)2.42 Tc Gutter Flow (minutes) =4.1 Tc Total =9.3 (5 minute minimum) Page 8 of 21 DRAINAGE AREA #EX2 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Hardscape 0.95 35155 33397 Landscape 0.2 0 0 Total 35155 33397 A = Area (acres)0.8070 C = Weighted C Factor 0.95 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.0% Return (yrs)Cf C = Rational Method Runoff Coefficient 0.35 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)15 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)5.2 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft)0.13 (0.15' below top of curb) S = slope (%)0.72% L = length of gutter (ft)400 V = mean velocity (ft/s)2.54 Tc Gutter Flow (minutes) =2.6 Tc Total =7.8 (5 minute minimum) Page 9 of 21 APPENDIX C POND SIZING CALCULATIONS Page 10 of 21 DETENTION POND #1 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 52151 49544 Landscape 0.2 0 0 Total 52151 49544 A = Area (acres)1.1972 C = Weighted C Factor 0.95 3. Calculate Tc (Pre-Development) Tc (Pre-Development) (minutes)9.3 4. Calculate Rainfall Intensity (Duration = Pre-Development Tc) i = 0.64x-0.65 (10-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs)0.16 (Tc Pre-Development - DA EX1) i = rainfall intensity (in./hr.)2.15 5. Calculate Runoff Rate (Pre-Development) Q = CiA C = Rational Method Runoff Coefficient 0.2 (open land) i = rainfall intensity (in./hr.) 2.15 (calculated above) A = Area (acres) 1.20 (calculated above) Q = Runoff Rate (Pre-Development) (cfs) 0.51 Page 11 of 21 6. Calculate Required Pond Volume Total Area (acres) = 1.20 acres Weighted C = 0.95 Discharge Rate (cfs) = 0.51 cfs (Equal to Pre-Development Runoff Rate) Duration(min) Duration(hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3) 16 0.27 1.51 1.72 1650 494 1156 17 0.28 1.45 1.65 1685 525 1161 18 0.30 1.40 1.59 1719 555 1164 19 0.32 1.35 1.54 1752 586 1166 20 0.33 1.31 1.49 1784 617 1167 21 0.35 1.27 1.44 1815 648 1167 22 0.37 1.23 1.40 1845 679 1166 23 0.38 1.19 1.36 1873 710 1164 24 0.40 1.16 1.32 1902 741 1161 25 0.42 1.13 1.29 1929 771 1157 OUTLET STRUCTURE SLOT Q=CLH3/2 Q = Discharge (cfs)0.51 (calculated above) C = Weir Coefficient 3.33 (per COB Design Standards) H = Head (ft)1.5 L = Horizontal Length (ft)0.08 L = Slot Width (inches)1.0 Page 12 of 21 DETENTION POND #2 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 161701 153616 Landscape 0.2 109161 21832 Total 270862 175448 A = Area (acres)6.2181 C = Weighted C Factor 0.65 3. Calculate Tc (Pre-Development) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.24% Return (yrs)Cf C = Rational Method Runoff Coefficient 0.2 2 to 10 1 Cf = Frequency Adjustment Factor 1 11 to 25 1.1 D = Length of Basin (ft)1115 26 to 50 1.2 51 to 100 1.25 Tc (Pre-Development) (minutes)52 4. Calculate Rainfall Intensity (Duration = Pre-Development Tc) i = 0.64x-0.65 (10-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs)0.87 (Tc Pre-Development) i = rainfall intensity (in./hr.)0.70 5. Calculate Runoff Rate (Pre-Development) Q = CiA C = Rational Method Runoff Coefficient 0.2 (open land) i = rainfall intensity (in./hr.) 0.70 (calculated above) A = Area (acres) 6.22 (calculated above) Q = Runoff Rate (Pre-Development) (cfs) 0.87 Page 13 of 21 6. Calculate Required Pond Volume Total Area (acres) = 6.22 acres Weighted C = 0.65 Discharge Rate (cfs) = 0.87 cfs (Equal to Pre-Development Runoff Rate) Duration(min) Duration(hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3) 59 0.98 0.65 2.61 9225 3080 6145 60 1.00 0.64 2.58 9280 3133 6147 61 1.02 0.63 2.55 9334 3185 6149 62 1.03 0.63 2.52 9387 3237 6150 63 1.05 0.62 2.50 9440 3289 6151 64 1.07 0.61 2.47 9492 3341 6151 65 1.08 0.61 2.45 9544 3394 6150 66 1.10 0.60 2.42 9595 3446 6149 67 1.12 0.60 2.40 9645 3498 6147 68 1.13 0.59 2.38 9695 3550 6145 OUTLET STRUCTURE SLOT Q=CLH3/2 Q = Discharge (cfs)0.87 (calculated above) C = Weir Coefficient 3.33 (per COB Design Standards) H = Head (ft)1.5 L = Horizontal Length (ft)0.14 L = Slot Width (inches)1.7 Page 14 of 21 APPENDIX D STORM SEWER FACILITIES DESIGN Page 15 of 21 PIPE #1 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 52151 49544 Landscape 0.2 0 0 Total 52151 49544 A = Area (acres)1.1972 C = Weighted C Factor 0.95 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.16 DA #EX1 i = rainfall intensity (in./hr.) 2.57 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.95 (calculated above) i = rainfall intensity (in./hr.) 2.57 (calculated above) A = Area (acres) 1.20 (calculated above) Q = 25-yr Flow Rate (cfs) 2.92 Page 16 of 21 MANNING'S EQUATION FOR PIPE FLOW Project: Pipe 1 Location: Detention Pond 1 Outlet Pipe INPUT D= 15 inches d= 14.07 inches Mannings Formula n= 0.013 mannings c 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.004 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.01 1.20 3.30 0.36 3.68 4.39 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D Page 17 of 21 PIPE #2 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 161701 153616 Landscape 0.2 109161 21832 Total 270862 175448 A = Area (acres)6.2181 C = Weighted C Factor 0.65 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.35 DA #1 i = rainfall intensity (in./hr.) 1.53 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.65 (calculated above) i = rainfall intensity (in./hr.) 1.53 (calculated above) A = Area (acres) 6.22 (calculated above) Q = 25-yr Flow Rate (cfs) 6.15 Page 18 of 21 MANNING'S EQUATION FOR PIPE FLOW Pipe: Pipe 2 Location: Detention Pond 2 Outlet Pipe INPUT D= 15 inches d= 14.07 inches Mannings Formula n= 0.013 mannings C 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.01 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 1.20 3.30 0.36 5.81 6.95 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D Page 19 of 21 APPENDIX E BAXTER CREEK DOWNSTREAM INFRASTRUCTURE Page 20 of 21 Page 21 of 21 _____________________________________________________________________________________ 1 November 20, 2019 Sarah Rosenberg Associate Planner City of Bozeman 20 East Olive St. PO Box 1230 Bozeman, MT 59771 RE: The Nest Cottages, Phase 1 Review Conformance: Wetland and Watercourse Regulations (Re-Issue of November 29, 2018 and September 4, 2019 Analyses) ______________________________________________________________________________________ Dear Sarah, On November 17, 2019 you requested a final review of The Nest Cottages (Phase 1) revised submittal materials concerning watercourse regulations. Two delineation maps with illustrated watercourse buffer zones and trail location were resubmitted. A highlighted version of the aerial overlay map is included below to illustrate areas of remaining concern. The following is an analysis of the resubmittal. Development Submittal Analysis:  One map features an aerial overlay and the other is an identical map with no aerial. Both maps are identified as “EX1”. The north arrow of these maps appears to be in error.  Most of the length of an unofficial trail meanders back and forth across the west property boundary within the Zone 1 watercourse buffer (see enclosed photos). o Even though a minor portion of the trail is technically off property, the location of the trail requires reconciliation in order to meet watercourse buffer regulations (trails should be located within Zone 2).  The proposed detention pond on the south end of the project is in its proper place (Zone 2).  On the north end of the project site development plans indicate encroachment into Zone 2; this encroachment requires adjustment of the proposed plan or a request for relaxation of the watercourse regulations.  The “Overall Landscape Plan” illustrates shrub and tree plantings within Zone 1. Quantities of each and total length of Zone 1 within the site is required to adequately analyze adherence to regulations.  The following comment was included in the original watercourse regulation analysis; it is unknown if this issue remains relevant, please provide information regarding this issue and how the issue will be reconciled in relation to bullet two above: The north end of the proposed new trail system is parallel to an existing trail located in the setback zones. The proponent is proposing an ADA-complaint boardwalk section in this new trail system. Materials and the need to construct a parallel trail will be discussed with the City. Please contact me with any questions (406-580-6993; lbacon@terraquaticllc.com ). I am available for meetings with the developer, city planners, or to attend Commission meetings. Sincerely, Lynn M. Bacon, PWS TerraQuatic, LLC 614 west Lamme Street Bozeman, MT 59715 The Nest Watercourse Regualtion Analysis November 20, 2019 _____________________________________________________________________________________ 2 Photo 1. Wetland delienation flag (pink oval) and wetland/upland boundary (red line); unofficial trail is currently located within Zone 1 (view south). The permanent trail, as proposed by the development plans, will remain in its curent location. Photo 2. Trail appears unofficial however some fines were noted (view south). The Nest Watercourse Regualtion Analysis November 20, 2019 _____________________________________________________________________________________ 3 Bozeman Ladder Truck Bozeman Ladder Truck Boze m a n L ad d e r T r u c k Bozem a n L ad d er T r u c k AASHTO - Single-Unit [SU] AASHTO - Single-Unit [SU] AASHTO - Single-Unit [SU] AASH T O - S i n g l e -U n i t [ SU ] AASHT O - S in g le - Un i t [ SU ] DESIGN REPORT WATER & SEWER MANAGEMENT THE NEST PUD SUBDIVISION Prepared for: Center Arrow Partners, LLC P.O. Box 1633, Bozeman, MT 59771 Prepared by: C&H Engineering and Surveying, Inc. 1091 Stoneridge Drive, Bozeman, MT 59718 (406) 587-1115 Project Number: 180805 May 2019 INTRODUCTION The proposed Nest PUD Subdivision is a 15-lot condominium subdivision located on Lot R1, Block 5, Westbrook Subdivision, Phase 4 (5.41-acres) in the Westbrook Subdivision. This project will require connection to existing City of Bozeman water and sanitary sewer systems. WATER SYSTEM LAYOUT The Nest PUD Subdivision will extend the existing 8” class 51 ductile iron water main installed in Glenwood Drive and Annie Street and will tap into the existing 8” water main running along Durston Road. All new water mains are to be installed in the City standard location and will be located 10’ away from any proposed sewer mains. All water mains will be looped and no blowoffs will be required with this layout. A WaterCAD analysis is enclosed at the end of the report analyzing the 8-inch water main extension installed with this project. The connection to the existing system was modeled as a pump curve using data obtained from the City of Bozeman Water Department: static, residual and pitot pressures were read at hydrants #2005 and #1985, located at the intersections of Annie Street/Twin Lakes Ave and Annie Street/Rosa Way, respectively. This data was used to develop the pump curve used at the connection point to model the existing system. The following equation based off of the Hazen Williams method is used to generate the pump curve: Q = Qf x ((Ps - P) / (Ps - Pr))0.54 Where: Q = flow predicted at desired residual pressure, Qf = total flow measured during test, Pr= residual pressure during test, Ps = static pressure and P = residual pressure at the desired flow rate. In the model, the pump is connected to a reservoir which acts as a source of water. The elevation of the reservoir is fixed at the elevation of the pump, which is also equivalent to the elevation of the tie-in point. The reservoir does not create any head on the system; the head is generated entirely by the pumps. The input data and the pump curves are included at the end of the report. The pump curve table includes all calculations and equations used in determining flow characteristics at the connection point. A C-factor of 130 was chosen for ductile iron class 51 pipe. WATER DISTRIBUTION SYSTEM SIZING Residential Units: Average Daily Residential Usage = 170 gallons per capita per day Average Population Density = 2.17 persons/dwelling unit Minimum Fire Hydrant Flow = 1,500 gpm Residual Pressure Required = 20 psi for Fire Flow Average Day Demand (Peaking Factor = 1) Maximum Day Demand (Peaking Factor = 2.3) Maximum Hour Demand (Peaking Factor = 3.0) Residential Water Demands (Demand Junction 1) Average Day Demand = 33 d.u. x 2.17 persons/d.u. x 170 gpcpd = 12,240 gpd = 8.5 gpm Maximum Day Demand = 8.5 gpm x 2.3 = 19.4 gpm Peak Hour Demand = 8.5 gpm x 3.0 = 25.4 gpm Residential Water Demands (Demand Junction 2) Average Day Demand = 12 d.u. x 2.17 persons/d.u. x 170 gpcpd = 4,464 gpd = 3.1 gpm Maximum Day Demand = 3.1 gpm x 2.3 = 7.1 gpm Peak Hour Demand = 3.1 gpm x 3.0 = 9.2 gpm Available Pressure: 8-inch class 51 ductile iron main Annie Street and Rosa Way Static = 96 psi (Hydrant #2005) Residual = 88 psi (Hydrant #2005) Pitot (2.5” nozzle) = 80 (Hydrant #1985) Flowing = 1,500 gpm (Hydrant #1985) HYDRAULIC ANALYSIS A water distribution model was created using WaterCAD Version 10.01.00.72 for demand Design Report - Page 4 of 8 forecasting and describing domestic and fire protection requirements. In order to model the system, each junction node of the water distribution system was assessed a demand based on its service area. The table shown below quantifies the demands placed at the junction nodes and calculates the demands for Average Day, Maximum Day and Peak Hour within the subdivision. The peaking factor for each case is 1, 2.3 and 3.0 respectively. The Nest PUD Subdivision (Table 1): DEMAND JUNCTION NODE DWELLING UNITS (D.U.) POPULATION (RES.) 2.17 PEOPLE PER D.U. AVERAGE DAY GPM (170 GALLONS PER DAY PER PERSON) MAX. DAY GPM PEAK HOUR GPM DJ 1 33 72 8.5 19.4 25.4 DJ 2 12 26 3.1 7.1 9.2 Total 45 98 11.53 26.51 34.58 *See Demand Junction Map for more information on which lots contribute to each Demand Junction. CONCLUSION The proposed 8-inch DIP water mains provide adequate capacity to serve the subdivision under the Peak Hour Demand condition. The flows and pressures within the system for the Peak Hour Demands were generated with the WaterCAD program and can be found in Appendix A. The capacity of the system to meet fire flow requirements was tested by running a steady state fire flow analysis for all junctions at fire hydrant locations. The model shows that all hydrant junctions satisfy fire flow constraints (residual pressure > 20 psi, flow rate > 1500 gpm), while providing service to lots at peak hour. The results of the analysis at peak hourly flow are given in Appendix A. SANITARY SEWER SYSTEM An 8-inch PVC sanitary sewer line will be installed in the woonerf section and will flow north to connect with the existing 8-inch stub located just south of the Annie Street/Cassandra Lane intersection. Design Report - Page 5 of 8 DESIGN REQUIREMENTS The flow rates used herein are according to the City of Bozeman Design Standards and Specifications Policy (DSSP) dated March, 2004. The peaking factor for the design area is determined by figuring the equivalent population and inserting the population into the Harmon Formula. An 8-inch main is used because that is the minimum diameter allowed within the City of Bozeman. Using the city average of 2.17 persons per household the equivalent population is calculated. Connection: Equivalent Population = (2.17 persons/dwelling unit)(45 units) = 98 persons Harmon Formula: Peaking Factor = (18 + P0.5)/(4 + P0.5) where: P = Population in thousands Peaking Factor = (18 + 0.0980.5)/(4 + 0.0980.5) Peaking Factor = 4.25 Assumed infiltration rate = 150 gallons/acre/day = 150 (5.41 acres) = 812 gal/day The peak flow rate is calculated by multiplying the City's design generation rate of 89 gallons per capita per day by the population, multiplying by the peaking factor, and adding the infiltration rate: Peak Flow Rate = 65 gpcpd (98 persons) (4.25) + 812 gpd = 27,885 gpd = 19.36 gpm = 0.0431 cfs The capacity of an 8-inch main is checked using Manning’s Equation: Qfull = (1.486/0.013)AR2/3S1/2 For an 8-inch PVC main: Manning's n = 0.013 for PVC Pipe Minimum Slope = 0.004 ft/ft A = area = (3.14/4)d 2 = (3.14/4)(8/12)2 = 0.34907 ft2 Design Report - Page 6 of 8 P = perimeter = 2(3.14)r = 2(3.14)(4/12) = 2.0944 ft R = hydraulic radius = A/P = 0.34907/2.0944 = 0.16667 ft R2/3 = 0.30105 ft S = 0.004 ft/ft S1/2 = 0.0632 ft/ft Qfull = (1.486/0.013)(0.34907)(0.30105)(0.0632) = 0.7592 cfs Connection: Q/Qfull = 0.0431 /0.7592 = 0.0568 or 5.68% Based on these calculations, an 8-inch sewer line has adequate capacity to carry the design flows for the subdivision. Design Report - Page 7 of 8 APPENDIX A WATERCAD MODEL Scenario Summary Report Scenario: Base Scenario Summary 1ID BaseLabel Notes Base Active TopologyActive Topology Base PhysicalPhysical Base DemandDemand Base Initial SettingsInitial Settings Base OperationalOperational Base AgeAge Base ConstituentConstituent Base TraceTrace Base Fire FlowFire Flow Base Energy CostEnergy Cost Base TransientTransient Base Pressure Dependent DemandPressure Dependent Demand Base Failure HistoryFailure History Base SCADASCADA Base User Data ExtensionsUser Data Extensions Base Calculation OptionsSteady State/EPS Solver Calculation Options Base Calculation OptionsTransient Solver Calculation Options Hydraulic Summary Steady StateTime Analysis Type TrueUse simple controls during steady state? Hazen-WilliamsFriction Method FalseIs EPS Snapshot? 0.001Accuracy 12:00:00 AMStart Time 40Trials Fire FlowCalculation Type Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72] Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Pump Definition Detailed Report: HYD 1985 Element Details 49ID Notes HYD 1985Label Pump Curve Head(ft)Flow(gpm) 221.540 207.691,284 196.151,781 184.622,181 173.082,526 161.542,835 150.003,117 138.463,379 126.923,625 115.383,858 103.854,079 92.314,290 80.774,493 69.234,688 57.694,876 46.155,059 34.625,236 23.085,408 11.545,576 0.005,739 Pump Efficiency Type Best Efficiency Point Pump Efficiency Type %100.0Motor Efficiency %100.0BEP Efficiency FalseIs Variable Speed Drive? gpm0BEP Flow Transient (Physical) lb·ft²0.000Inertia (Pump and Motor)SI=25, US=1280Specific Speed rpm0Speed (Full)TrueReverse Spin Allowed? Page 1 of 227 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72] Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Pump Definition Detailed Report: HYD 1985 Page 2 of 227 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72] Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Scenario: Base P-6P-4P-1P-3Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1[10.01.00.72]Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg FlexTable: Pipe Table Headloss Gradient (ft/ft) Hydraulic Grade (Stop) (ft) Hydraulic Grade (Start) (ft) Velocity (ft/s) Flow (gpm) Minor Loss Coefficient (Unified) Hazen-Williams C MaterialDiameter (in) Length (User Defined) (ft) Label 0.0004,975.474,975.510.22353.060130.0Ductile Iron8.0824P-3 0.0004,975.474,975.470.0000.390130.0Ductile Iron8.022P-5 0.0004,975.474,975.470.0691.580130.0Ductile Iron8.0521P-6 0.0004,754.004,754.000.00350.000150.0PVC999.01P-1 0.0004,975.514,975.520.22351.880130.0Ductile Iron8.0430P-2 0.0004,975.474,975.470.0000.000130.0Ductile Iron6.010P-4 Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72]Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Fire Flow Node FlexTable: Fire Flow Report Junction w/ Minimum Pressure (System) Pressure (Calculated Zone Lower Limit) (psi) Pressure (Zone Lower Limit) (psi) Pressure (Calculated Residual) (psi) Pressure (Residual Lower Limit) (psi) Flow (Total Available) (gpm) Flow (Total Needed) (gpm) Fire Flow (Available) (gpm) Fire Flow (Needed) (gpm) Label DJ-219020202,2781,5002,2781,500HYD-1 Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72]Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg FlexTable: Junction Table Pressure (psi) Hydraulic Grade (ft) Demand (gpm) Demand CollectionElevation (ft) Label 934,975.4725<Collection: 1 items>4,760.00DJ-1 914,975.479<Collection: 1 items>4,765.00DJ-2 934,975.470<Collection: 0 items>4,760.00HYD-1 964,975.510<Collection: 0 items>4,754.50J-2 924,975.470<Collection: 0 items>4,762.00J-4 Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72] Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Design Report - Page 8 of 8 APPENDIX B DEMAND JUNCTION MAP Attn: Addi Jadin City of Bozeman Planning Department 20 East Olive, Suite 202 Bozeman, MT 59715 Re: The Nest Cottages, Phase 1; Waters of the US Description; Baxter Creek from Durston Road to Annie Street March 6, 2018 Dear Ms. Jadin: The owners of the Nest Cottages parcel is proposing to develop small homes on R-1 lots located in Block 5 of Phase 4 of the Westbrook Subdivision located in Bozeman, Montana. The parcel boundaries are identified on Sheet C1.0, Overall Site Plan, for The Nest Cottages Phase 1 drafted by C&H Engineering and Surveying. The development is owned by Center Arrow Partners, LLC, and is legally described as Section 4, Township 2 South, Range 5 East, Gallatin County. The Nest Cottages parcel is located east of the Baxter Creek riparian corridor, which includes 50-foot watercourse setbacks required by the City’s Development Standards for Watercourse Setbacks addressed in Section 38.23.100 of the Unified Development Code (Sheet C1.0). Setbacks for developments under review after July 10, 2002, require a minimum 50-foot setback along both sides of a watercourse. The setbacks are to include wetlands immediately adjacent to a watercourse, defined as a perennial stream. The creek, wetland fringe, and 50-foot watercourse setbacks are located outside the west parcel boundary. However, based on City regulations, the boundaries of wetlands and watercourses within 100 feet of the parcel boundary must be identified on the preliminary plat drawings. Previous waters of the US and wetland delineations on Baxter Creek were completed by Vaughn Environmental Services, certified wetland scientist, on June 24, 2008, and September 26, 2017 The second delineation was completed for Creekstone Condominiums on the Baxter Creek reach extending from Oak Street to Glenellen Drive. The owners have requested that Vaughn Environmental Services verify that the wetland boundaries associated with the Baxter Creek reach extending north from the south boundary of the Nest Cottages’ parcel to Annie Street have not been impacted by development since the 2008 delineation. Note that the south boundary of the Nest Cottage borders a mitigation site constructed as part of the original 404 permit that is protected from development. The only impacts to the Baxter Creek corridor that have occurred since 2008 are within the ROW for Annie Street. The wetland fringe boundary associated with the creek corridor located west of the Nest Cottage parcel within 100 feet of the west boundary will be verified by Vaughn Environmental Services during the 2018 growing season, likely in May or June 2018. Baxter Creek is considered a WUS by the US Army Corps of Engineers (USACE) based on the downgradient connection to the East Gallatin River. The Gallatin County Conservation District classifies the creek as a perennial stream. The field investigation will be completed to determine the boundary of the wetland fringe associated with Baxter Creek in order to define the 50-foot watercourse setbacks required by the City of Bozeman. Based on planning information provided by the engineer and architect, the proposed project will not impact or affect Baxter Creek or the adjacent wetland fringe and, therefore, will not require 310 or 404 permits. The boundaries of WUS and wetlands within the study area will be identified using methodology developed by the USACE and other federal agencies for implementation of Section 404 of the Clean Water Act. Delineation procedures involve a review of existing site-specific information and completion of an onsite field investigation based on guidelines for the Routine Determination Method presented in the Field Guide for Wetland Delineation (Environmental Laboratory 1987) and the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (USACE 2010). Please contact my office at 406 581-0655 or at bvaughn@montana.com if you require additional information. Thank you. Sincerely, Barbara Vaughn Environmental Engineer, MS Photo 1.0 View is of upland test pit SP-1 looking northeast toward Baxter Creek corridor. Photo 2.0 View is of wetland test pit SP-2 located at the edge of Baxter Creek. Photo 3.0 View is of Baxter Creek looking north from Glenellen Drive.