Loading...
HomeMy WebLinkAbout15-4 Drainage Report Phase 4 Apts 04-05-2021Page 1 of 4 Storm Drainage Calculations Bozeman Gateway – Phase 4 Apartments January 27, 2021 1 Introduction This summary report provides hydrologic and hydraulic calculations for sizing of detention storage facilities and other storm drainage structures for development of the Bozeman Gateway Phase 4 Apartments, in accordance with the City of Bozeman Design Standards. The proposed site consists of a four-apartment located south east of the intersection of Harmon Stream and Technology Blvd. The purpose of the report and calculations is to demonstrate the following: - Post- development peak runoff does not exceed pre-construction (historic) conditions for the 10-year storm event - The 25-year peak runoff is conveyed by underground storm drain facility with no surface overflow - Storm water treatment is provided to intercept and contain sediment and floating debris on site, for eventual removal and disposal. 2 Drainage Basins Bozeman Gateway Phase 4 includes a drainage area of approximately 8.7 acres (378,887 ft2). Pre-development topography is gradual, about 1 to 2 percent slope from south to north. Existing groundcover is undeveloped, previously agricultural fields. The proposed property can be divided into flows that will be contained on-site (Basins 2 and 3), direct runoff (Basin 4) and off-site flows that have been accounted for within previously approved drainage submittals (Basin 1 and 5). The previous submittals are as follows and are attached at the end of this report. - Storm Drainage Calculations Bozeman Gateway – AED Building Site Plan, December 27, 2017 - Storm Drainage Calculations Bozeman Gateway – Building “G” Overflow Parking Site Plan Refer to Figure 1 for pre-development drainage basins and Figure 2 for post- development basins. On Site Flows – Basins 2 & 3 Pre-development sub-basin H2 corresponds to developed Basin 2 which is comprised of sub-basins D2.1 through D2.14. The proposed use of an underground detention facility within Basin 2 will limit the post-development 10-year peak runoff to the pre- development rate from sub-basin H2. Predevelopment sub-basin H3 corresponds to developed Basin 3 which is comprised of sub-basins D3.1 through D3.8. The proposed use of an underground detention facility within Basin 3 will limit the post-development 10-year peak runoff rate to the pre- development rate from sub-basin H3. Page 2 of 4 Direct Runoff – Basin 4 Basin 4 which includes sub-basin D4.1 and D4.2 are part of the Phase 4 Open Space and is primarily a vegetative area with an existing swale flowing south to north. The runoff from Basin 4 cannot be intercepted onsite; these areas drain offsite as direct runoff, similar to existing conditions. Off-site Flows – Basin 1 & 5 Pre-development sub-basin H1 corresponds to developed Basin 1 which includes basins D1.1 to D1.3. The flows from D1.1 to D1.3 in Phase 4 are included as part of the flows to the existing underground storage system in the parking lot of Site G per Storm Drainage Calculations Bozeman Gateway – Building “G” Overflow Parking Site Plan provided at the end of this report. Pre-development sub-basin H5 corresponds to developed sub-basin D5.1. The flows from D5.1 are included as part of the flows to the existing underground storage system in the AED parking lot per Storm Drainage Calculations Bozeman Gateway – AED Building Site Plan. 3 Approach It will be shown that for the proposed development in Basins 2 & 3, the use of existing and proposed detention and treatment facilities will limit the post-development 10-year peak runoff rate to the pre-development rate, and will provide effective treatment of storm runoff. All storm drain pipes have been sized to convey the 25-year peak runoff. The Rational Method was used to calculate peak runoff and detention requirements in accordance with City of Bozeman design standards. The peak runoff table (See Appendix) is an Excel spreadsheet with formulas that calculate post-development discharge values. The values used in each column of the table are as follows: Area: Calculated in AutoCAD from Figures 1 and 2 C (Rational Method runoff coefficient): Runoff coefficients were calculated using 0.20 for pervious areas (pre-development and developed landscape areas) and 0.90 for impervious areas (pavement, concrete and rooftops). Pro-rating by area resulted in the coefficients used in the calculations. Tc (time of concentration) Five minutes is the minimum value used in the Rational Method. Some of the smaller sub-basins would calculate to less than 5 minutes. Peak Runoff Values (Q2 through Q100) Values were calculated using the Rational Method formula (Q = CiA) and the intensity formulas in the City’s design standards (Rainfall Intensity – Duration Curves) 3 Detention Phase 4 of the Bozeman Gateway project will utilize two existing and two proposed underground detention and treatment facilities for its stormwater runoff. Basins 1 and 5 Page 3 of 4 will utilize existing systems that were previously slightly oversized to allow flexibility when designing storm water facilities for future phases of development. Basin 2 and 3 will drain to proposed stormtech pre-fabricated underground storage and infiltration systems within each Basin. For the 10-year design storm, post-development peak flows and detention volumes are estimated using the Rational Method in accordance with City of Bozeman Design Standards. The StormTech system will include an inlet manhole that doubles as access for cleaning the isolator (sediment accumulation) row of the system. Basin 2 The detention facility for Basin 2 will discharge through a 24” PVC pipe to a control structure housed in a manhole. The detention outlet control structure will consist of a vertical tee with a 5” diameter (or a 42/5” square) orifice on the bottom and a 27” diameter vertical riser to pass runoff exceeding the 10-year storage maximum water surface elevation into the piped storm drain system. The top of the overflow riser will be set at elevation level with the top of the 36” storage depth (top of stone backfill). Excess runoff from larger, less frequent storm events will overtop the vertical tee, to the 25-year maximum depth indicated in Table 1. Basin 3 The detention facility for Basin 3 will discharge through an 21” PVC pipe to a control structure housed in a manhole. The detention outlet control structure will consist of a vertical tee with a 4” diameter (or a 3½” square) orifice on the bottom and a 24” diameter vertical riser to pass runoff exceeding the 10-year storage maximum water surface elevation into the piped storm drain system. The top of the overflow riser will be set at elevation level with the top of the 36” storage depth (top of stone backfill). Excess runoff from larger, less frequent storm events will overtop the vertical tee, to the 25-year maximum depth indicated in Table 1. TABLE 1 - Detention Basin Data Description Detention Basin Name D2 D3 Max. 10-yr Release Rate (cfs) 1.04 0.68 Min. Required Detention Volume (cu. ft.) 6,199 4,259 Sizes and Dimensions: vertical tee (riser) dia., inches 27 24 outlet pipe dia., inches 24 21 Orifice (two alternates): circular orifice dia., inches 5” 4” rectangular (proposed replacement) 42/5” x 42/5” 3½” x 3½” Elevations: 25-yr WSEL at control structure 49.60 52.67 top of riser (=10-yr max. WSEL) 48.93 52.00 discharge pipe invert at control structure 45.93 49.00 Supporting calculations are attached. Design Details are provided on the construction drawings. Page 4 of 4 4 Conveyance The storm drain piping system for the proposed development is designed to convey flows from a 25-year storm. Provisions for overland flow of larger, less frequent storms up to the 100-year storm will be incorporated into the site grading. Calculations are provided for representative pipes as required to assure pipe size is adequate for all pipes; adequacy of other pipe sizes are evident based on the calculated sub-basin areas and flow rates for the representative pipes. See Appendix for the conveyance calculations for the storm drain pipes within Phase 4. Design details will be provided on the construction drawings. 5 Storm Water Treatment The City’s design standards require Low Impact Development (LID) practices that infiltrate, evapotranspire or capture runoff, to the extent feasible, for a specified design runoff event. This requirement is addressed using existing and proposed StormTech underground detention and storage facilities. These systems combine infiltration and runoff capture. The StormTech system is a widely accepted LID practice found to remove 80 percent of total suspended solids from municipal storm runoff. It meets LEED criteria for storm water treatment (SS6.2 water quality credit). The facilities for this project provide over 6 inches of capture depth for infiltration and runoff volume reduction, plus treatment of additional runoff by deposition as water slowly travels through the long, linear rows of chambers and gravel base. The system solves the problem of runoff “short-circuiting” from inlet to outlet that is inherent in surface detention ponds. Runoff from the first ½” of rainfall will percolate through and fill a gravel filter before finding its way to a perforated low-flow outlet pipe that discharges into the detention outlet structure. Additional runoff from larger storms can bypass this discharge route, but only after storage depth reaches 2 feet (this correlates to about 64 percent of the total available storage volume). Although the detention calculations assume zero infiltration, the existing alluvial (gravel/pit run) soils directly under the StormTech systems provide excellent infiltration, which further improves treatment. We believe this type of treatment not only meets, but exceeds, the City’s current design standards.    PEAK RUNOFF AND DETENTION CALCULATIONS    (this page left blank intentionally) Bozeman Gateway Phase 4 Apartments Peak Runoff Calculations MODIFIED RATIONAL METHOD i = A * (Tc/60) B Qp = C i A Qp = peak runoff, cfs Design Coefficients C = runoff coefficient Storm A B i = A(Tc/60)B (Bozeman IDF curve)2-yr 0.36 -0.60 Tc = time of concentration, minutes 5-yr 0.52 -0.64 A = Area, acres 10-yr 0.64 -0.65 25-yr 0.78 -0.64 50-yr 0.92 -0.66 Retention Volume = 7,200*(C)*(i)*(A), where i = 0.41 in./hr 100-yr 1.01 -0.67 (Bozeman Design Standards, March 2004) Retention Sub-Basin Name Area C Tc Q2 Q5 Q10 Q25 Q50 Q100 Volume (ft.3) Basin 1 H1 1.83 0.20 29.70 0.20 0.30 0.37 0.45 0.54 0.59 D1.1 0.70 0.82 5.00 0.91 1.45 1.83 2.18 2.70 3.04 D1.2 1.02 0.70 5.00 1.14 1.82 2.29 2.72 3.38 3.80 D1.3 0.11 0.25 5.00 0.04 0.07 0.09 0.11 0.13 0.15 D1 Total 1.83 0.71 5.00 2.09 3.34 4.21 5.01 6.21 6.99 3,865 Basin 2 H2 5.18 0.20 30.20 0.56 0.84 1.04 1.25 1.50 1.66 D2.1 0.24 0.90 5.00 0.34 0.54 0.68 0.81 1.01 1.13 D2.2 0.24 0.90 5.00 0.34 0.54 0.68 0.81 1.01 1.13 D2.3 0.20 0.20 5.00 0.06 0.10 0.13 0.16 0.19 0.22 D2.4 0.27 0.20 5.00 0.09 0.14 0.17 0.20 0.25 0.29 D2.5 0.21 0.90 5.00 0.30 0.48 0.61 0.72 0.90 1.01 D2.6 0.21 0.90 5.00 0.30 0.48 0.61 0.72 0.90 1.01 D2.7a 0.15 0.74 5.00 0.18 0.28 0.35 0.42 0.52 0.59 D2.7b 0.89 0.72 6.00 0.92 1.46 1.84 2.19 2.71 3.04 D2.8 0.32 0.72 5.00 0.37 0.60 0.75 0.90 1.11 1.25 D2.9 0.15 0.82 5.00 0.20 0.32 0.40 0.48 0.59 0.66 D2.10 0.26 0.90 5.00 0.38 0.60 0.76 0.90 1.12 1.26 D2.11 0.79 0.68 5.00 0.86 1.37 1.72 2.05 2.54 2.86 D2.12 0.58 0.85 5.00 0.79 1.27 1.60 1.90 2.36 2.65 D2.13 0.19 0.87 5.00 0.27 0.43 0.54 0.64 0.80 0.90 D2.14 0.47 0.72 5.00 0.54 0.86 1.08 1.29 1.60 1.80 D2 Total 5.18 0.74 5.00 6.15 9.81 12.37 14.71 18.24 20.52 11,350 Basin 3 H3 3.32 0.20 29.30 0.37 0.55 0.68 0.82 0.98 1.08 D3.1 0.82 0.70 5.00 0.92 1.47 1.85 2.20 2.73 3.07 D3.2 0.72 0.82 5.00 0.94 1.49 1.88 2.24 2.78 3.12 D3.3 0.26 0.90 5.00 0.38 0.60 0.76 0.90 1.12 1.26 D3.4 0.21 0.90 5.00 0.30 0.49 0.61 0.73 0.90 1.02 D3.5 0.21 0.90 5.00 0.30 0.49 0.61 0.73 0.90 1.02 D3.6 0.27 0.84 5.00 0.37 0.58 0.74 0.88 1.09 1.22 D3.7a 0.03 0.90 5.00 0.05 0.08 0.10 0.12 0.15 0.17 D3.7b 0.70 0.78 5.00 0.87 1.38 1.75 2.07 2.57 2.89 D3.8 0.10 0.20 5.00 0.03 0.05 0.06 0.07 0.09 0.10 D3 Total 3.32 0.78 5.00 4.15 6.62 8.35 9.92 12.30 13.84 7,656 Basin 4 H4 0.92 0.20 5.00 0.30 0.47 0.60 0.71 0.88 0.99 D4.1 0.57 0.86 5.00 0.78 1.25 1.58 1.88 2.33 2.62 D4.2 0.36 0.80 5.00 0.46 0.73 0.92 1.09 1.35 1.52 D4 Total 0.92 0.84 5.00 1.24 1.98 2.50 2.97 3.68 4.14 2,292 Basin 5 H5 0.04 0.20 8.00 0.01 0.01 0.02 0.02 0.03 0.03 D5.1 0.04 0.90 5.00 0.05 0.08 0.11 0.13 0.16 0.18 97 Bozeman Gateway Phase 4 Apartments Basin 2 (Sub-Basin D2.1 to D2.14) Detention (10-yr storm) MODIFIED RATIONAL METHOD Qp = C i A POST-DEVELOPMENT PRE-DEVEL. 5.18 AC Qp (Basin H1) = 1.04 cfs 0.74 5.0 MIN D2 release rate = 1.04 cfs 3.22 IN/HR TIME STEP 12.37 CFS DURATION = 5.0 min. Max. Volume, Max. Volume,Required Detention Triangle Rel. (cu. ft.) Constant Rel. (cu. ft.)Volume (cu. ft.) 7399.13 4998.74 6,199 Triangle Release Constant Release DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN) (IN/HR) (CFS) (CF) (CF) 4.75 3.33 12.79 3,342 3,063 9.75 2.09 8.02 4,230 3,810 14.75 1.59 6.13 4,805 4,241 19.75 1.32 5.07 5,232 4,524 ORIFICE CALCULATIONS 24.75 1.14 4.38 5,569 4,715 MATCHING Qp = 1.04 cfs 29.75 1.01 3.88 5,846 4,845 Max. Depth = 2.50 ft 34.75 0.91 3.51 6,077 4,929 39.75 0.84 3.22 6,273 4,978 44.75 0.77 2.98 6,442 4,999 49.75 0.72 2.78 6,588 4,996 CIRCULAR ORIFICE: 54.75 0.68 2.61 6,715 4,975 DIAMETER = 5.0000 inches 59.75 0.64 2.47 6,825 4,936 Area = 0.14 ft 2 64.75 0.61 2.34 6,921 4,884 ORIFICE FLOW = 1.04 CFS 69.75 0.58 2.23 7,005 4,819 74.75 0.55 2.13 7,078 4,742 79.75 0.53 2.05 7,142 4,656 RECTANGULAR ORIFICE: 84.75 0.51 1.97 7,196 4,561 LENGTH = 4.400 inches 89.75 0.49 1.89 7,243 4,458 WIDTH = 4.400 inches 94.75 0.48 1.83 7,282 4,347 Area = 0.13 ft 2 99.75 0.46 1.77 7,315 4,230 ORIFICE FLOW = 1.02 CFS 104.75 0.45 1.71 7,342 4,107 109.75 0.43 1.66 7,363 3,978 114.75 0.42 1.61 7,379 3,844 119.75 0.41 1.57 7,390 3,704 124.75 0.40 1.53 7,397 3,561 WEIR CALCULATIONS (not used) 129.75 0.39 1.49 7,399 3,413 Coefficient = 3.33 inches 134.75 0.38 1.45 7,398 3,261 Width = 1.1000 inches 139.75 0.37 1.42 7,393 3,105 WEIR FLOW = 1.21 CFS 144.75 0.36 1.39 7,384 2,946 149.75 0.35 1.36 7,372 2,783 154.75 0.35 1.33 7,357 2,617 159.75 0.34 1.30 7,339 2,448 164.75 0.33 1.28 7,319 2,277 169.75 0.33 1.25 7,295 2,102 174.75 0.32 1.23 7,270 1,926 179.75 0.31 1.21 7,241 1,746 184.75 0.31 1.18 7,211 1,565 189.75 0.30 1.16 7,178 1,381 194.75 0.30 1.14 7,143 1,195 199.75 0.29 1.13 7,107 1,007 204.75 0.29 1.11 7,068 816 209.75 0.28 1.09 7,027 625 214.75 0.28 1.07 6,985 431 219.75 0.28 1.06 6,941 235 224.75 0.27 1.04 6,895 38 POST-DEV Qp = POND VOLUME CALCULATIONS: BASIN AREA POST = POST-DEV Tc = POST-DEV C = STORM INTENSITY = User Inputs Chamber Model: SC-740 Outlet Control Structure: No Project Name: Engineer: Celine Saucier Project Location: Measurement Type: Imperial Required Storage Volume: 6199 cubic ft. Stone Porosity: 40% Stone Foundation Depth: 6 in. Stone Above Chambers: 6 in. Average Cover Over Chambers: 18 in. Design Constraint Dimensions:(17 ft. x 115 ft.) Results System Volume and Bed Size Installed Storage Volume: 3759.20 cubic ft. Storage Volume Per Chamber: 45.90 cubic ft. Number Of Chambers Required: 45 Number Of End Caps Required: 6 Chamber Rows: 3 Maximum Length:114.28 ft. Maximum Width: 15.75 ft. Approx. Bed Size Required: 1799.93 square ft. System Components Amount Of Stone Required: 156.82 cubic yards Volume Of Excavation (Not Including Fill): 233.32 cubic yards User Inputs Chamber Model: SC-740 Outlet Control Structure: No Project Name: Engineer: Celine Saucier Project Location: Measurement Type: Imperial Required Storage Volume: 4000 cubic ft. Stone Porosity: 40% Stone Foundation Depth: 6 in. Stone Above Chambers: 6 in. Average Cover Over Chambers: 18 in. Design Constraint Dimensions:(22 ft. x 75 ft.) Results System Volume and Bed Size Installed Storage Volume: 3045.82 cubic ft. Storage Volume Per Chamber: 45.90 cubic ft. Number Of Chambers Required: 36 Number Of End Caps Required: 8 Chamber Rows: 4 Maximum Length:71.58 ft. Maximum Width: 20.50 ft. Approx. Bed Size Required: 1467.42 square ft. System Components Amount Of Stone Required: 129.02 cubic yards Volume Of Excavation (Not Including Fill): 190.22 cubic yards Bozeman Gateway Phase 4 Apartments Basin 3 (Sub-Basin D3.1 to D3.8) Detention (10-yr storm) MODIFIED RATIONAL METHOD Qp = C i A POST-DEVELOPMENT PRE-DEVEL. 3.32 AC Qp (Basin H2) = 0.68 cfs 0.78 5.0 MIN D1.2 release rate = 0.68 cfs 3.22 IN/HR TIME STEP 8.35 CFS DURATION = 5.0 min. Max. Volume, Max. Volume,Required Detention Triangle Rel. (cu. ft.) Constant Rel. (cu. ft.)Volume (cu. ft.) 5080.70 3436.52 4,259 Triangle Release Constant Release DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN) (IN/HR) (CFS) (CF) (CF) 4.75 3.33 8.63 2,261 2,078 9.75 2.09 5.41 2,863 2,587 14.75 1.59 4.13 3,254 2,885 19.75 1.32 3.42 3,545 3,081 ORIFICE CALCULATIONS 24.75 1.14 2.95 3,776 3,216 MATCHING Qp = 0.68 cfs 29.75 1.01 2.62 3,966 3,310 Max. Depth = 2.50 ft 34.75 0.91 2.37 4,125 3,373 39.75 0.84 2.17 4,261 3,412 44.75 0.77 2.01 4,378 3,432 49.75 0.72 1.87 4,479 3,437 CIRCULAR ORIFICE: 54.75 0.68 1.76 4,568 3,428 DIAMETER = 4.000 inches 59.75 0.64 1.66 4,646 3,408 Area = 0.09 ft 2 64.75 0.61 1.58 4,714 3,379 ORIFICE FLOW = 0.66 CFS 69.75 0.58 1.51 4,774 3,341 74.75 0.55 1.44 4,827 3,296 79.75 0.53 1.38 4,872 3,244 RECTANGULAR ORIFICE: 84.75 0.51 1.33 4,912 3,186 LENGTH = 3.500 inches 89.75 0.49 1.28 4,947 3,123 WIDTH = 3.500 inches 94.75 0.48 1.23 4,977 3,054 Area = 0.09 ft 2 99.75 0.46 1.19 5,002 2,982 ORIFICE FLOW = 0.65 CFS 104.75 0.45 1.16 5,023 2,905 109.75 0.43 1.12 5,041 2,824 114.75 0.42 1.09 5,055 2,739 WEIR CALCULATIONS (not used) 119.75 0.41 1.06 5,066 2,652 Coefficient = 3.33 inches 124.75 0.40 1.03 5,074 2,561 Width = 0.6000 inches 129.75 0.39 1.01 5,078 2,467 WEIR FLOW = 0.66 CFS 134.75 0.38 0.98 5,081 2,371 139.75 0.37 0.96 5,080 2,272 144.75 0.36 0.94 5,078 2,171 149.75 0.35 0.92 5,073 2,068 154.75 0.35 0.90 5,066 1,962 159.75 0.34 0.88 5,058 1,855 164.75 0.33 0.86 5,047 1,745 169.75 0.33 0.84 5,034 1,634 174.75 0.32 0.83 5,020 1,521 179.75 0.31 0.81 5,004 1,406 184.75 0.31 0.80 4,987 1,290 189.75 0.30 0.79 4,968 1,172 194.75 0.30 0.77 4,948 1,053 199.75 0.29 0.76 4,926 932 204.75 0.29 0.75 4,903 810 209.75 0.28 0.74 4,879 687 214.75 0.28 0.72 4,854 563 219.75 0.28 0.71 4,828 437 224.75 0.27 0.70 4,800 310 229.75 0.27 0.69 4,771 182 234.75 0.26 0.68 4,742 54 POND VOLUME CALCULATIONS: BASIN AREA POST = POST-DEV C = POST-DEV Tc = STORM INTENSITY = POST-DEV Qp = User Inputs Chamber Model: SC-740 Outlet Control Structure: Yes Project Name: Engineer: Celine Saucier Project Location: Measurement Type: Imperial Required Storage Volume: 4259 cubic ft. Stone Porosity: 40% Stone Foundation Depth: 6 in. Stone Above Chambers: 6 in. Average Cover Over Chambers: 18 in. Design Constraint Dimensions:(13 ft. x 225 ft.) Results System Volume and Bed Size Installed Storage Volume: 4388.67 cubic ft. Storage Volume Per Chamber: 45.90 cubic ft. Number Of Chambers Required: 50 Number Of End Caps Required: 4 Chamber Rows: 2 Maximum Length:185.45 ft. Maximum Width: 11.60 ft. Approx. Bed Size Required: 2151.20 square ft. System Components Amount Of Stone Required: 193.86 cubic yards Volume Of Excavation (Not Including Fill): 278.86 cubic yards Bozeman Gateway Phase 4 Apartments Pipe Calculations (25-yr storm) MODIFIED RATIONAL METHOD Qp = C i A Qp = 25-yr peak runoff, cfs C = runoff coefficient i = 0.78(Tc/60)-0.64 (Bozeman IDF curve) Tc = time of concentration, minutes A = Area, acres Conveyance Pipe (Ex2) Contributing Basins Area1 C Tc Qpipe 2 (cfs)Pipe Dia. & Slope Pipe Capacity3 (cfs) Basin 2 1 D2.2 0.24 0.90 5.00 0.81 8" @ 1% slope 1.41 2 D2.6 0.21 0.90 5.00 0.72 8" @ 1% slope 1.41 3 D2.3, D2.6 0.41 0.56 5.00 0.88 8" @ 1% slope 1.41 4 D2.2, D2.3, D2.4, D2.6 0.92 0.54 5.00 1.90 12" @ 0.5% slope 2.91 5 D2.5 0.21 0.90 5.00 0.72 8" @ 3.3% slope 2.57 6 D2.5, D2.7a 0.36 0.83 5.00 1.14 8" @ 3.3% slope 2.57 7 D2.2, D2.3, D2.4, D2.5, D2.6, D2.7a 1.28 0.62 5.00 3.04 12" @ 1.5% slope 5.04 8 D2.1 0.24 0.90 5.00 0.81 8" @ 3.8% slope 2.76 9 D2.9 0.15 0.82 5.00 0.48 8" @ 0.5% slope 1 10 D2.1, D2.8, D2.9 0.71 0.80 5.00 2.18 12" @ 0.5% slope 2.91 11 D2.1-D2.9 2.88 0.72 5.00 7.92 15" @ 1.25% slope 8.34 12 D2.10 0.26 0.90 5.00 0.90 8" @ 2.4% slope 2.19 13 D2.10, D2.11 1.05 0.73 5.00 2.95 12" @ 2% slope 5.82 14 D2.1-D2.12 4.52 0.74 5.00 12.78 21" @ 0.68% slope 15.2 15 D2.1-D2.12, D2.14 4.99 0.74 5.00 14.07 21" @ 0.68% slope 15.2 16 D2.1-D2.14 5.18 0.74 5.00 14.71 21" @ 0.68% slope 15.2 Discharge Pipe D2.1-D2.14 5.18 0.74 5.00 14.71 24" @ 0.5% slope 20.34 18 D3.1 0.82 0.70 5.00 2.20 12" @ 1% slope 4.11 19 D3.1, D3.7a 0.86 0.71 5.00 2.32 12" @ 0.9% slope 3.90 20 D3.5 0.21 0.90 5.00 0.73 8" @ 4.3% slope 2.93 21 D3.5, D3.8 0.31 0.68 5.00 0.80 8" @ 1.0% slope 1.41 22 D3.7b 0.70 0.73 5.00 1.95 8" @ 2.4% slope 2.19 23 D3.1, D3.5, D3.7a, D3.7b, D3.8 1.86 0.73 5.00 5.20 24" @ 1% slope 26.12 24 D3.2 0.72 0.82 5.00 2.24 12" @ 1.2% slope 4.51 25 D3.3 0.26 0.90 5.00 0.90 8" @ 1.0% slope 1.41 26 D3.4 0.21 0.90 5.00 0.73 8" @ 4.5% slope 2.99 27 D3.3, D3.4, D3.6 0.75 0.88 5.00 2.51 12" @ 1.0% slope 4.11 28 D3.2, D3.3, D3.4, D3.6 1.46 0.85 5.00 4.75 15" @ 1.0% slope 7.46 Discharge Pipe D3.1-D3.8 3.32 0.78 5.00 9.92 21" @ 0.5% slope 14.24 FOOTNOTES: 1. Contributing drainage area (conservatively high in some cases) 2. Qpipe is the total 25-year peak runoff (direct surface runoff plus flows from upstream pipes) to the pipe draining the indicated structure/flow entry point. 3 Capactiy is determined using Flowmaster to calculate maximum flow through the pipe at the specified diameter and slope. Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.011 Channel Slope 0.00500 ft/ft Diameter 2.00 ft Discharge 14.71 ft³/s Results Normal Depth 1.33 ft Flow Area 2.21 ft² Wetted Perimeter 3.81 ft Hydraulic Radius 0.58 ft Top Width 1.89 ft Critical Depth 1.38 ft Percent Full 66.3 % Critical Slope 0.00447 ft/ft Velocity 6.65 ft/s Velocity Head 0.69 ft Specific Energy 2.01 ft Froude Number 1.08 Maximum Discharge 20.34 ft³/s Discharge Full 18.90 ft³/s Slope Full 0.00303 ft/ft Flow Type SuperCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 66.31 % Downstream Velocity Infinity ft/s 24" PVC, Basin 2 Discharge, 25-yr 2/3/2021 10:08:37 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page GVF Output Data Upstream Velocity Infinity ft/s Normal Depth 1.33 ft Critical Depth 1.38 ft Channel Slope 0.00500 ft/ft Critical Slope 0.00447 ft/ft 24" PVC, Basin 2 Discharge, 25-yr 2/3/2021 10:08:37 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.011 Channel Slope 0.00500 ft/ft Diameter 1.75 ft Discharge 9.92 ft³/s Results Normal Depth 1.13 ft Flow Area 1.64 ft² Wetted Perimeter 3.27 ft Hydraulic Radius 0.50 ft Top Width 1.67 ft Critical Depth 1.17 ft Percent Full 64.6 % Critical Slope 0.00450 ft/ft Velocity 6.04 ft/s Velocity Head 0.57 ft Specific Energy 1.70 ft Froude Number 1.08 Maximum Discharge 14.24 ft³/s Discharge Full 13.24 ft³/s Slope Full 0.00281 ft/ft Flow Type SuperCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 64.55 % Downstream Velocity Infinity ft/s 21" PVC, Basin 3 Discharge, 25-yr 2/3/2021 10:19:32 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page GVF Output Data Upstream Velocity Infinity ft/s Normal Depth 1.13 ft Critical Depth 1.17 ft Channel Slope 0.00500 ft/ft Critical Slope 0.00450 ft/ft 21" PVC, Basin 3 Discharge, 25-yr 2/3/2021 10:19:32 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page VERIFY SCALE! THESE PRINTS MAY BE REDUCED. LINE BELOW MEASURES ONE INCH ON ORIGINAL DRAWING. MODIFY SCALE ACCORDINGLY! 2021COPYRIGHT © MORRISON-MAIERLE, INC., SHEET NUMBER PROJECT NUMBER DRAWING NUMBER DATEDESCRIPTIONNO.BY N:\6558\002.02\ACAD\EXHIBITS\PRE DEVELOPMENT STORM.DWG PLOTTED BY:CELINE SAUCIER ON Feb/03/2021 REVISIONS DRAWN BY: DSGN. BY: APPR. BY: DATE: Q.C. REVIEW DATE: BY: 2880 Technology Blvd West Bozeman, MT 59718 406.587.0721 www.m-m.net engineers surveyors planners scientists MorrisonMaierle BOZEMAN GATEWAY PUD PHASE 4 APARTMENTSBOZEMAN MT PRE-DEVELOPMENT DRAINAGE BASINS 6558.002 FIG 1 JAU 50 10025500 SCALE IN FEET NOT FOR CONSTRUCTION DECEMBER 30, 2020 LEGEND SUB-BASIN BOUNDARY POST-DEVELOPMENT BASIN DESIGNATION BASIN AREA (ACRES) X.X X.XX Ac. EEFOFOSDTV TVF F F TV P P PP P P E SD SD SD SD SD SD SD SD LOT 1 BLOCK 6 378,887 SqFt 8.7 ACRES VERIFY SCALE! THESE PRINTS MAY BE REDUCED. LINE BELOW MEASURES ONE INCH ON ORIGINAL DRAWING. MODIFY SCALE ACCORDINGLY! 2021COPYRIGHT © MORRISON-MAIERLE, INC., SHEET NUMBER PROJECT NUMBER DRAWING NUMBER DATEDESCRIPTIONNO.BY N:\6558\002.02\ACAD\EXHIBITS\POST DEVELOPMENT STORM.DWG PLOTTED BY:CELINE SAUCIER ON Feb/03/2021 REVISIONS DRAWN BY: DSGN. BY: APPR. BY: DATE: Q.C. REVIEW DATE: BY: 2880 Technology Blvd West Bozeman, MT 59718 406.587.0721 www.m-m.net engineers surveyors planners scientists MorrisonMaierle BOZEMAN GATEWAY PUD PHASE 4 APARTMENTSBOZEMAN MT POST-DEVELOPMENT DRAINAGE BASINS 6558.002 FIG 2 JAU 50 10025500 SCALE IN FEET NOT FOR CONSTRUCTION DECEMBER 30, 2020 LEGEND BASIN BOUNDARY POST-DEVELOPMENT SUB-BASIN DESIGNATION SUB-BASIN AREA (ACRES) X.X X.XX Ac. FLOW DIRECTION 1 23 4 56 7 8 9 10 11 13 14 15 16 12 18 19 20 21 22 24 25 23 26 27 28 BASIN 1 - NOT PART OF THIS SITE PLAN APPLICATION BASIN 2 BASIN 3 BASIN 4 BASIN 5 SUB-BASIN BOUNDARY    APPENDIX - PREVIOUS DRAINGE REPORTS (this page left blank intentionally) AED DRAINAGE REPORT (this page left blank intentionally) Page 1 of 3 Storm Drainage Calculations Bozeman Gateway - AED Building Site Plan December 27, 2017 1 Introduction This summary report provides hydrologic and hydraulic calculations for sizing of detention storage facilities and other storm drainage structures for development of the AED Building Site, in accordance with the City of Bozeman Design Standards. The site is located within the mixed commercial/residential Bozeman Gateway development south of the Gallatin Valley Mall, at the southwest corner of Technology Boulevard West and South 29th Avenue. The proposed development includes a parking lot south of the building site, and adjacent access drives connecting to existing streets. Pre-development topography is gradual, sloping about 1.5 to 2 percent from south to north. Existing ground cover is undeveloped, previously agricultural fields. 2 Approach For the purposes of this report, the “study area” covers currently proposed and all future development of the area bordered by Garfield Street, South 29th Avenue, Technology Boulevard and the un-named drainage/open space to the west. Previous Bozeman Gateway site plan submittals include the Kohl’s Site Plan, with drainage report dated May 26, 2010. The Kohl’s drainage basin fully encompasses the study area. The original plan was to drain storm runoff from the entire study area east to the South 29th Avenue storm drain for treatment and detention in the large “StormTech” pre-fabricated underground storage and infiltration facility under the Kohl’s parking lot, which was sized for fully developed conditions. However, due to site grading constraints it is now proposed to divert 0.72 acres of the 4.30-acre study area to a new (proposed) StormTech facility that will drain west to the un-named drainage, rather than east to the existing South 29th Avenue storm drain. Calculations are provided for the proposed new system and its pre- and post-development drainage basins. The remainder of the study area (3.58 acres) will be connected to the existing South 29th Avenue storm drain as originally planned. 3 Detention Sub-Basin D1: Pre-development sub-basin H1 (see Figure 1) corresponds to developed sub-basins D1.1, D1.2 and D1.3 (see Figure 2). Sub-basin D1 will drain to a new StormTech facility, to an inlet manhole that doubles as access for removing accumulated sediment. An inspection port allows monitoring of sediment levels in the system. The StormTech facility will provide storm water treatment and will limit the post-development 10-year peak runoff rate (sub-basins D1.1 through D1.3) to the pre-development rate (sub-basin H1). In a 10-year or smaller storm event, all runoff will be stored in the StormTech facility and will discharge through an outlet control structure housed in a discharge manhole. The outlet control structure will consist of a 12” diameter vertical tee with a 2½” diameter (or a 2½” x 2” rectangular) orifice on the bottom and a vertical 12” pipe extension (riser) above the tee. The top of the overflow riser will be set equal to the Page 2 of 3 10-year maximum water surface elevation (51.20), to pass runoff exceeding the 10-year maximum water surface elevation into the piped storm drain system. The head required to pass the 25-year peak runoff of 2.21 cfs over the riser is 0.39 feet, which is low enough to ensure piped conveyance of the 25-year peak runoff to the un-named drainage. Detention volume and pipe sizing calculations are attached. Design details will be provided on the construction drawings Sub-Basin D2: Pre-development sub-basin H2 (see Figure 1) corresponds to developed sub-basins D2.1 through D2.5 (see Figure 2). The existing detention facility under the Kohl’s parking lot will provide storm water treatment and will limit the post-development 10-year peak runoff rate (sub-basins D2.1 through D2.5) to the pre-development rate (sub-basin H2). Previous calculations (Kohl’s Site Plan), combined with the reduction in basin size (area diverted to Sub-Basin D1), show that the existing Kohl’s system meets the required design criteria for Sub-Basin D2. Pipe sizing calculations are attached. Design details will be provided on the construction drawings. 4 Treatment The City’s design standards require Low Impact Development (LID) practices that infiltrate, evapotranspire or capture runoff, to the extent feasible, for a specified design runoff event. The proposed StormTech facility combines infiltration and runoff capture. The StormTech system is a widely accepted LID practice found to remove 80 percent of total suspended solids from municipal storm runoff. It meets LEED criteria for storm water treatment (SS 6.2, water quality credit). All surface runoff will enter the underground storage facilities in an “isolator row” that is designed for sediment removal as part of regular operation and maintenance. The StormTech faciliy proposed for this project will provide 6 inches of capture depth for infiltration and runoff volume reduction, plus treatment of additional runoff by deposition as water slowly travels through the long row of chambers. The system solves the problem of runoff “short-circuiting” from inlet to outlet that is inherent in surface detention ponds. Runoff from the first ½” of rainfall will be completely captured for infiltration to a depth of 6 inches. Above this depth, infiltration will combine with percolation laterally through a gravel filter at a very low velocity before finding its way to a perforated low-flow outlet pipe that discharges into the detention outlet structure. Additional runoff from larger storms (those exceeding the 10-year design storm) can bypass this discharge route, but only after storage depth reaches 2 feet. For the proposed system, the 2 feet correlates to a total storage volume of 578 cubic feet before untreated runoff could bypass the gravel filter. Although the detention calculations assume zero infiltration, the existing alluvial (gravel/pit run) soils directly under the proposed StormTech system provide excellent infiltration, which further improves treatment. We believe this type of treatment not only meets, but exceeds, the City’s current design standards. 5 Conveyance The proposed storm drain system is shown on Figure 2. Ditches and pipes have been sized to convey the 25-year peak runoff through the site. Provisions for overland flow of larger, less frequent storms up to the 100-year storm will be incorporated into the site grading. Calculations are provided for representative pipes as required to assure pipe Page 3 of 3 size is adequate for all pipes; adequacy of other pipe sizes are evident based on the calculated sub-basin areas and flow rates for the representative pipes. Design details will be provided on the construction drawings. Future phase development south of the site was taken into consideration in the placement and sizing of pipes and inlets, with three stubs included for future connections to the system. Final drainage design for future phases will be provided at the time of development. Until these future phases are constructed, “Run-on” flows from this currently undeveloped area will be directed west to a temporary sediment basin, and then continue north to the un-named drainage. N:\3638\009\Design Docs\Drainage\Bldg. W\Drainage Report.docx (this page left blank intentionally)    PEAK RUNOFF AND DETENTION CALCULATIONS Bozeman Gateway, Building W Site Plan Peak Runoff Calculations MODIFIED RATIONAL METHOD i = A * (Tc/60) B Qp = C i A Qp = peak runoff, cfs Design Coefficients C = runoff coefficient Storm AB i = A(Tc/60)B (Bozeman IDF curve)2-yr 0.36 -0.60 Tc = time of concentration, minutes 5-yr 0.52 -0.64 A = Area, acres 10-yr 0.64 -0.65 25-yr 0.78 -0.64 50-yr 0.92 -0.66 100-yr 1.01 -0.67 (Bozeman Design Standards, March 2004) Sub-Basin Name Area C Tc Q2 Q5 Q10 Q25 Q50 Q100 Basin 1 H1 0.72 0.20 10.30 0.15 0.23 0.29 0.35 0.42 0.47 D1.1 0.22 0.83 5.00 0.29 0.47 0.59 0.70 0.87 0.98 D1.2 0.36 0.76 5.00 0.44 0.70 0.89 1.05 1.31 1.47 D1.3 0.14 0.90 5.00 0.20 0.32 0.41 0.48 0.60 0.67 D1 total 0.72 0.80 5.00 0.92 1.47 1.86 2.21 2.74 3.08 Basin 2 D2.1A 0.33 0.81 5.00 0.43 0.68 0.86 1.02 1.26 1.42 D2.1B 0.18 0.65 5.00 0.19 0.30 0.37 0.45 0.55 0.62 D2.2 1.06 0.65 5.10 1.08 1.73 2.18 2.59 3.21 3.61 D2.3 0.66 0.88 5.00 0.92 1.47 1.86 2.21 2.74 3.08 D2.4 0.40 0.78 5.00 0.50 0.79 1.00 1.19 1.48 1.66 D2.5 0.95 0.83 5.00 1.26 2.01 2.53 3.01 3.73 4.20 D2.1(A+B) 0.51 0.84 5.00 0.68 1.09 1.38 1.64 2.03 2.28 D(2.4+2.5) 1.35 0.63 5.00 1.36 2.16 2.73 3.24 4.02 4.53 D(2.3+2.4+2.5) 2.01 0.83 5.00 2.68 4.27 5.39 6.41 7.95 8.94 D2 total 3.58 0.78 5.00 4.46 7.11 8.98 10.67 13.23 14.89 Time of Concentration, Sub-Basin H1 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Range (natural).: 0.13 50.00 ft 2.00% 0.1300 1.20 in 8.20 min Shallow Short grass, pasture and lawns (n=0.030) 95.00 ft 1.40% 0.0300 1.25 min Channel (interm) Grassed (n=0.030) 105.00 ft 1.60% 0.0300 0.81 min Pervious TC 10.26 min   Time of Concentration, Sub-Basin D2.2 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet asphalt: 0.012 20.00 ft 3.00% 0.0120 1.20 in 0.50 min Channel (interm) concrete gutter 630.00 ft 0.50% 0.0120 3.50 min Channel (interm) concrete gutter 260.00 ft 0.80% 0.0120 1.14 min Pervious TC 5.14 min Bozeman Gateway, Building W Site Plan Runoff Coefficients Area Area (sq. ft.) Runoff Sub-Basin (acres) Total Pervious Impervious Coefficient Basin 1 H1 0.72 31,363 31,363 0 0.20 D1.1 0.22 9,583 898 8,685 0.83 D1.2 0.36 15,682 3,033 12,649 0.76 D1.3 0.14 6,098 0 6,098 0.90 D1 total 0.72 21,780 3,033 18,747 0.80 Basin 2 D2.1A 0.33 14,375 1,929 12,446 0.81 D2.1B 0.18 7,841 0 7,841 0.90 D2.2 1.06 46,174 16,693 29,481 0.65 D2.3 0.66 28,750 1,013 27,737 0.88 D2.4 0.40 17,424 3,046 14,378 0.78 D2.5 0.95 41,382 4,254 37,128 0.83 D2.1(A+B) 0.51 22,216 1,929 20,287 0.84 D(2.4+2.5) 1.35 58,806 16,693 37,321 0.63 D(2.3+2.4+2.5) 2.01 87,556 8,313 79,243 0.83 D2 total 3.58 155,945 26,935 129,010 0.78 Bozeman Gateway, Building W Site Plan Sub-Basin D1 Detention (10-yr storm) MODIFIED RATIONAL METHOD Qp = C i A POST-DEVELOPMENT PRE-DEVEL. 0.72 AC Qp (Basin H1) = 0.29 cfs 0.80 5.0 MIN D1.2 release rate = 0.29 cfs 3.22 IN/HR TIME STEP 1.86 CFS DURATION = 5.0 min. Max. Volume, Max. Volume,Required Detention Triangle Rel. (cu. ft.) Constant Rel. (cu. ft.)Volume (cu. ft.) 770.91 505.15 638 Triangle Release Constant Release DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN) (IN/HR) (CFS) (CF) (CF) 4.75 3.33 1.92 463 392 9.75 2.09 1.20 577 469 14.75 1.59 0.92 643 499 19.75 1.32 0.76 687 505 ORIFICE CALCULATIONS 24.75 1.14 0.66 718 498 MATCHING Qp = 0.29 cfs 29.75 1.01 0.58 739 481 Max. Depth = 3.00 ft 34.75 0.91 0.53 754 456 39.75 0.84 0.48 764 427 44.75 0.77 0.45 769 393 49.75 0.72 0.42 771 355 CIRCULAR ORIFICE: 54.75 0.68 0.39 770 315 DIAMETER = 2.500 inches 59.75 0.64 0.37 767 272 Area = 0.03 ft 2 64.75 0.61 0.35 761 226 ORIFICE FLOW = 0.28 CFS 69.75 0.58 0.34 754 179 74.75 0.55 0.32 745 130 79.75 0.53 0.31 734 79 RECTANGULAR ORIFICE (not used): 84.75 0.51 0.30 722 27 LENGTH = 2.500 inches 89.75 0.49 0.28 709 -26 WIDTH = 2.000 inches 94.75 0.48 0.27 695 -80 Area = 0.03 ft 2 99.75 0.46 0.27 680 -136 ORIFICE FLOW = 0.29 CFS 104.75 0.45 0.26 664 -192 109.75 0.43 0.25 647 -249 114.75 0.42 0.24 630 -307 119.75 0.41 0.24 611 -366 124.75 0.40 0.23 592 -426 WEIR CALCULATIONS (not used) 129.75 0.39 0.22 573 -486 Coefficient = 3.33 inches 134.75 0.38 0.22 552 -547 Width = 0.1875 inches 139.75 0.37 0.21 532 -609 WEIR FLOW = 0.27 CFS 144.75 0.36 0.21 510 -671 149.75 0.35 0.20 488 -733 154.75 0.35 0.20 466 -796 POST-DEV Qp = POND VOLUME CALCULATIONS: BASIN AREA POST = POST-DEV Tc = POST-DEV C = STORM INTENSITY = DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN) (IN/HR) (CFS) (CF) (CF) 159.75 0.34 0.20 444 -860 164.75 0.33 0.19 420 -924 169.75 0.33 0.19 397 -988 174.75 0.32 0.18 373 -1,053 179.75 0.31 0.18 349 -1,118 184.75 0.31 0.18 324 -1,184 189.75 0.30 0.17 299 -1,250 194.75 0.30 0.17 274 -1,316 199.75 0.29 0.17 248 -1,382 204.75 0.29 0.17 223 -1,449 209.75 0.28 0.16 196 -1,517 214.75 0.28 0.16 170 -1,584 219.75 0.28 0.16 143 -1,652 224.75 0.27 0.16 117 -1,720 229.75 0.27 0.15 89 -1,788 234.75 0.26 0.15 62 -1,857 239.75 0.26 0.15 35 -1,925 244.75 0.26 0.15 7 -1,994 249.75 0.25 0.15 -21 -2,063 254.75 0.25 0.14 -49 -2,133 259.75 0.25 0.14 -78 -2,202 264.75 0.24 0.14 -106 -2,272 269.75 0.24 0.14 -135 -2,342 274.75 0.24 0.14 -164 -2,413 279.75 0.24 0.14 -193 -2,483 284.75 0.23 0.13 -222 -2,554 289.75 0.23 0.13 -252 -2,624 294.75 0.23 0.13 -281 -2,695 299.75 0.22 0.13 -311 -2,766 304.75 0.22 0.13 -341 -2,838 309.75 0.22 0.13 -371 -2,909 314.75 0.22 0.13 -401 -2,981 319.75 0.22 0.12 -432 -3,052 324.75 0.21 0.12 -462 -3,124 329.75 0.21 0.12 -493 -3,196 334.75 0.21 0.12 -523 -3,268 339.75 0.21 0.12 -554 -3,340 344.75 0.21 0.12 -585 -3,413 349.75 0.20 0.12 -616 -3,485 354.75 0.20 0.12 -647 -3,558 359.75 0.20 0.12 -679 -3,631 364.75 0.20 0.11 -710 -3,704 369.75 0.20 0.11 -741 -3,777 374.75 0.19 0.11 -773 -3,850 379.75 0.19 0.11 -805 -3,923 384.75 0.19 0.11 -837 -3,996 389.75 0.19 0.11 -868 -4,070 394.75 0.19 0.11 -900 -4,143 399.75 0.19 0.11 -933 -4,217 404.75 0.19 0.11 -965 -4,291 409.75 0.18 0.11 -997 -4,365 414.75 0.18 0.11 -1,029 -4,439 419.75 0.18 0.10 -1,062 -4,513 424.75 0.18 0.10 -1,094 -4,587 429.75 0.18 0.10 -1,127 -4,661 434.75 0.18 0.10 -1,160 -4,735 439.75 0.18 0.10 -1,192 -4,810 444.75 0.17 0.10 -1,225 -4,884 449.75 0.17 0.10 -1,258 -4,959 454.75 0.17 0.10 -1,291 -5,033 459.75 0.17 0.10 -1,324 -5,108 464.75 0.17 0.10 -1,358 -5,183 Bozeman Gateway, Building W Site Plan Sub-Basin D1 Storage Calculations (10-yr storm) StormTech Sizing Calculations Required Storage Volume 638 ft3 StormTech Modules, Model No. SC740 (30" chamber height) Depth to top of gravel 36 in. installed storage volume 68.14 ft3 per chamber (see note 1) Number of chambers required 10 9.36 before rounding excess storage volume 6.4 % Number of chambers proposed 12 excess storage volume 22.0 % equal to (see note 2) 140 ft3 excess storage volume Installed chamber footprint (per chamber) = 5' x 7.12' Note: add 2' min. to each row, for end caps Storage Volume Provided = 778 ft3 Notes: 1. Storage volume assumes 6" of stone above and between chambers, and 40% stone porosity.    (this page left blank intentionally)    PIPE FLOW CALCULATIONS Bozeman Gateway, Building W Site Plan Pipe Calculations (25-yr storm) MODIFIED RATIONAL METHOD Qp = C i A Qp = 25-yr peak runoff, cfs C = runoff coefficient i = 0.78(Tc/60)-0.64 (Bozeman IDF curve) Tc = time of concentration, minutes A = Area, acres Basin Name Flow Entry Point Area1 CTcQpipe2 Pipe Dia.3 Basin 1 D1.1 total to curb inlet #1 0.22 0.83 5.00 0.70 12" D1.2 total to curb inlet #3 0.36 0.76 5.00 1.05 12" D1.3 future runoff to west temporary end cap 0.14 0.90 5.00 0.48 6" D1 total total 25-yr overflow, to riser in control MH 0.72 0.80 5.00 2.21 12" Basin 2 D2.1B future building roof drain, west of Bldg. W 0.18 0.65 5.00 0.45 6" - total to dry well #1 0.45 0.90 5.00 1.55 8" D2.1(A+B) total to drop inlet #1 0.51 0.84 5.00 1.64 12" D2.2 total to curb inlet #7 1.06 0.65 5.10 2.59 12" D2.3 future runoff to east temporaray end cap 0.66 0.88 5.00 2.21 12" D2.4 total to curb inlet #5 0.40 0.78 5.00 1.19 12" D2.5 total to manhole #3 0.95 0.83 5.00 3.01 12" D(2.4+2.5) total to curb inlet #6 1.35 0.63 5.00 3.24 12" D2 total total to manhole #4 3.58 0.78 5.00 10.67 18" FOOTNOTES: 1. Contributing drainage area (conservatively high in some cases) 2.Qpipe is the total 25-year peak runoff (direct surface runoff plus flows from upstream pipes) to the pipe draining the indicated structure/flow entry point. 3. Discharge pipe for the indicated flow entry point. Calculations are attached for pipes in bold text. Other pipe sizes are evident based on subbasin areas and flow rates in the above table. Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.011 Channel Slope 1.00000 % Diameter 6.00 in Discharge 0.48 ft³/s Results Normal Depth 0.32 ft Flow Area 0.13 ft² Wetted Perimeter 0.92 ft Hydraulic Radius 0.14 ft Top Width 0.48 ft Critical Depth 0.35 ft Percent Full 63.1 % Critical Slope 0.00730 ft/ft Velocity 3.68 ft/s Velocity Head 0.21 ft Specific Energy 0.53 ft Froude Number 1.25 Maximum Discharge 0.71 ft³/s Discharge Full 0.66 ft³/s Slope Full 0.00524 ft/ft Flow Type SuperCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 63.08 % Downstream Velocity Infinity ft/s 6" PVC, 25-yr 12/27/2017 9:09:50 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.011 Channel Slope 2.00000 % Diameter 8.00 in Discharge 1.55 ft³/s Results Normal Depth 0.44 ft Flow Area 0.24 ft² Wetted Perimeter 1.26 ft Hydraulic Radius 0.19 ft Top Width 0.63 ft Critical Depth 0.58 ft Percent Full 65.7 % Critical Slope 0.01075 ft/ft Velocity 6.38 ft/s Velocity Head 0.63 ft Specific Energy 1.07 ft Froude Number 1.82 Maximum Discharge 2.17 ft³/s Discharge Full 2.02 ft³/s Slope Full 0.01178 ft/ft Flow Type SuperCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 65.66 % Downstream Velocity Infinity ft/s 8" PVC, 25-yr 12/27/2017 9:19:52 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.011 Channel Slope 0.60 % Diameter 12.00 in Discharge 3.24 ft³/s Results Normal Depth 0.81 ft Flow Area 0.68 ft² Wetted Perimeter 2.25 ft Hydraulic Radius 0.30 ft Top Width 0.78 ft Critical Depth 0.77 ft Percent Full 81.4 % Critical Slope 0.00669 ft/ft Velocity 4.73 ft/s Velocity Head 0.35 ft Specific Energy 1.16 ft Froude Number 0.89 Maximum Discharge 3.51 ft³/s Discharge Full 3.26 ft³/s Slope Full 0.00592 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 81.38 % Downstream Velocity Infinity ft/s 12" PVC, 25-yr 12/27/2017 9:25:40 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.011 Channel Slope 1.00 % Diameter 18.00 in Discharge 10.67 ft³/s Results Normal Depth 1.07 ft Flow Area 1.35 ft² Wetted Perimeter 3.02 ft Hydraulic Radius 0.45 ft Top Width 1.36 ft Critical Depth 1.25 ft Percent Full 71.4 % Critical Slope 0.00714 ft/ft Velocity 7.90 ft/s Velocity Head 0.97 ft Specific Energy 2.04 ft Froude Number 1.39 Maximum Discharge 13.35 ft³/s Discharge Full 12.41 ft³/s Slope Full 0.00739 ft/ft Flow Type SuperCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 71.44 % Downstream Velocity Infinity ft/s 18" PVC, 25-yr 12/27/2017 9:25:10 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page (this page left blank intentionally)    DRAINAGE MAPS (this page left blank intentionally) SS SS SS SS SS SS SS SS SS SS SSSSSSSSWWWW W W W W W W W W W W W W W W W W WWWSSSSSSSSSSWSS SS SSSSWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWFOFOW 4850 4850 48554855 48554849 4849 4851 48 5 1 48524852 48524852 4852 4 8 5 2 48534 8 5 3 4853 485 3485348534853 485448 5 4 4854 4856485648564857485748574858 4854 48554860 4859485848574857 485648554853485248524853PRE-DEVELOPMENT DRAINAGE BASINSBOZEMAN GATEWAY, AED BUILDING SITE PLANLEGENDSUB-BASIN BOUNDARYPRE-DEVELOPMENTSUB-BASIN DESIGNATIONSUB-BASIN AREA (ACRES)XXX.XX Ac.SOUTH 29TH AVENUEGARFIELD STREETFIGURE NUMBER©PROJECT NO.DRAWN BY:DSGN. BY:APPR. BY:DATE:COPYRIGHT MORRISON-MAIERLE, INC.,2017N:\6110\001_AED Building\ACAD\Exhibits\DRAINAGE_PRE.dwg Plotted by mike g. hickman on Dec/27/2017engineers surveyors planners scientistsMorrisonMaierle6110.001FIG. 1BOZEMANMONTANADSMGH---12/2017TECHNOLOGY BLVD.2880 Technology Blvd WestBozeman, MT 59718Phone: 406.587.0721Fax: 406.922.6702H23.58 Ac.H10.72 Ac.UN-NAMED DRAIN A G E FLOW DIRECTION             (this page left blank intentionally) LOT 1A100.445 SqFt2.31 ACRESLOT 341,668 SqFt0.96 ACRESSS SS SS SS SS SS SS SS SS SS SSSSSSSSWWWW W W W W W W W W W W W W W W W W WWWSSSSSSSSSSWSS SS SSSSWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWFOSD SDSDFOEEEEEEEEEEEEEEEEEEEEEEEEEEFOFOFOFOFOFOFOFOFOFOFOFOFO FO FO FO FO FO FO FO FO FO FO FO FOWWWWWWWWWW W 4850 4850 48554855 48554858 4854 48554860 4859485848574857 485648554853485248524853555554 . 5555454.55454 54 5454>>>>>>>>>>>>>>>>>>>>>>> > >POST-DEVELOPMENT DRAINAGE BASINSBOZEMAN GATEWAY, AED BUILDING SITE PLANLEGENDSUB-BASIN BOUNDARYPOST-DEVELOPMENTSUB-BASIN DESIGNATIONSUB-BASIN AREA (ACRES)X.XX.XX Ac.SOUTH 29TH AVENUEGARFIELD STREETFIGURE NUMBER©PROJECT NO.DRAWN BY:DSGN. BY:APPR. BY:DATE:COPYRIGHT MORRISON-MAIERLE, INC.,2017N:\6110\001_AED Building\ACAD\Exhibits\DRAINAGE_POST.dwg Plotted by mike g. hickman on Dec/27/2017engineers surveyors planners scientistsMorrisonMaierle6110.001FIG. 2BOZEMANMONTANACJFMGH---12/2017TECHNOLOGY BLVD.D2.21.06 Ac.2880 Technology Blvd WestBozeman, MT 59718Phone: 406.587.0721Fax: 406.922.6702D2.30.66 Ac.D2.40.40 Ac.D2.50.95 Ac.D2.1B0.18 Ac.D1.30.14 Ac.D2.1A0.33 Ac.(EX IST ING)(EXIST ING)(FUTURE PHASE)(FUTURE PHASE ) (FUTURE PHASE)(EXIST ING )(EXISTING)(CURRENTLY PROPOSED)(FUTURE PHASE)D1.10.22 Ac.UN-NAMED DRAINAGEFLOW DIRECTIONPHASE LINECONNECT TO EXISTING29TH AVE. STORM DRAINOUTLET CONTROLMANHOLE(SEE NOTE 2)UNDERGROUNDDETENTION FACILITY(SEE NOTE 1)TEMP. ENDCAPTEMP. ENDCAPTEMP. ENDCAPD1.20.36 Ac.TEMP. DITCHTEMP. SEDIMENTPOND             (this page left blank intentionally) BUILDING “G” OVERFLOW PARKING DRAINAGE REPORT (this page left blank intentionally) Page 1 of 3 Storm Drainage Calculations Bozeman Gateway – Building “G” Overflow Parking Site Plan August 21, 2014 1 Introduction This summary report provides hydrologic and hydraulic calculations for sizing of detention storage and other storm drainage structures for development of the Building “G” overflow parking site within the Bozeman Gateway development, in accordance with the City of Bozeman Design Standards. The site is a proposed parking lot expansion in a retail development located south of the Gallatin Valley Mall. Pre-development topography is gradual, about 1 to 2 percent. Existing ground cover is undeveloped, previously agricultural fields. 2 Approach The preliminary drainage calculations in the Bozeman Gateway Phase 1, Block 2 application were used as a basis, as well as subsequent calculations for the nearby Kohl’s, City Brew/Qdoba, Building “S” and Building “G” developments. The open space south of Huffine Lane includes an existing storm drain system connected to a 36” pipe which drains to the north side of the Main Mall. This existing system will be extended to also convey the 25-year peak runoff from the site and upstream areas, while keeping 100-year overflow elevations well below any of the finished floor elevations. Pre-development sub-basin H1 (see Figure 1) corresponds to developed sub-basin D1 (see Figure 2). Sub-basin D1 will drain to a proposed underground detention facility which will first provide treatment and a significant amount of infiltration, and will also limit the post-development 10-year peak runoff rate to the pre-development peak rate. Runoff from areas south of Sub-basin D1 will be routed across Harmon Stream Boulevard through an existing 24” pipe installed for this purpose. Although over 80 percent of sub-basin D1 will be developed as a future phase, detention and treatment will be constructed for the entire sub-basin based on fully developed conditions, so that phasing of additional detention within this sub-basin will not be necessary. 3 Detention Sub-basin D1 will drain to a “StormTech” pre-fabricated underground storage and infiltration system. The StormTech system will include a hydraulic control vault that doubles as access for cleaning the isolator (sediment accumulation) row of the system. Inspection ports allow monitoring of sediment levels in the system. The system can be cleaned using standard pipe cleaning equipment for large diameter pipes. In a 10-year or smaller storm event, all runoff will be detained in the StormTech system to a maximum depth of 3 feet to overflow. The initial runoff from any storm will infiltrate to subsoils until ponding in the system reaches the detention outlet elevation. The additional runoff that doesn’t infiltrate will be collected by perforated pipe and routed to a 12” diameter drain pipe into the discharge side of the control vault; the pipe will have an end cap with a 6” diameter (or a 5½” x 51/8” rectangular) orifice to control runoff rate. Page 2 of 3 The control vault will consist of an inlet side for flow into the StormTech system, an overflow weir to pass runoff exceeding the 10-year maximum water surface elevation, and a discharge side leading to the existing storm drain system along Huffine Lane. The top of the overflow weir will be set at elevation 42.20, equal to the 10-year maximum water surface elevation of the detention storage facility. The head required to pass the 25-year peak runoff of 19.57 cfs over the weir is 1.0 feet. This is low enough to ensure underground, piped conveyance from the site to the 24” discharge pipe; it was also verified that the 24” pipe has capacity to convey the 25-year peak runoff. Detention volume and pipe sizing calculations are attached. Design details will be provided on the construction drawings. Page 3 of 3 Record Id: H1 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns.: 0.15 150.00 ft 1.80% 0.1500 1.20 in 23.08 min Shallow Short grass, pasture and lawns (n=0.030) 300.00 ft 1.60% 0.0300 3.69 min Channel (interm) Grassed (n=0.030) 320.00 ft 1.50% 0.0300 2.56 min Pervious TC 29.34 min Record Id: D1 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Smooth Surfaces.: 0.011 70.00 ft 0.50% 0.0110 1.20 in 2.59 min Channel (interm) Concrete pipe (n=0.012) 165.00 ft 1.00% 0.0120 0.65 min Channel (interm) Concrete pipe (n=0.012) 700.00 ft 1.00% 0.0120 2.75 min Channel (interm) Concrete pipe (n=0.012) 475.00 ft 1.00% 0.0120 1.86 min Pervious TC 7.85 min N:\3638\009\Design Docs\Drainage\Bldg. G\Drainage Report.doc Bozeman Gateway - Building G Overflow Parking Lot - Site Plan Sub-Basin H1 MMI#:3638.009.040.000318 DATE: ENGINEER: MODIFIED RATIONAL METHOD Qp = C i A PRE-DEVELOPMENT, BASIN H1 RAINFALL FREQ = 10 yr, 1 hr. BASIN AREA PRE = 8.03 acres STORM EVENT STORM i COEFF INTENSITY (YR)A B (IN/HR) PRE-DEV Tc = 29.3 min. 2 0.36 -0.60 0.55 5 0.52 -0.64 0.82 PRE-DEV C = 0.20 10 0.64 -0.65 1.02 25 0.78 -0.64 1.23 STORM A = 0.64 50 0.92 -0.66 1.48 B = -0.65 100 1.01 -0.67 1.63 STORM INTENSITY =1.02 IN/HR (Source: City of Bozeman Design Standards, March 2004) PRE-DEV Qp =1.64 CFS i = A * (Tc/60) B 8/21/14 Mike Hickman N:\3638\009\Design Docs\Drainage\Bldg. G overflow parking\drainage calcs.xlsx Bozeman Gateway - Building G Overflow Parking Lot - Site Plan Sub-Basin D1 Detention Facility MODIFIED RATIONAL METHOD Qp = C i A POST-DEVELOPMENT - BASIN D1 PRE-DEVEL. 8.03 AC Qp (Basin H1) = 1.64 cfs 7.9 MIN MATCHING Qp 0.85 (Basin H1) = 1.64 cfs 2.40 IN/HR TIME STEP 16.39 CFS DURATION = 5.0 min. Max. Volume, Max. Volume, REQUIRED DETENTION VOL. Triangle Rel. (cu. ft.) Constant Rel. (cu. ft.) (cu. ft.) 13928.02 9358.19 11,643 Triangle Release Constant Release DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN) (IN/HR) (CFS) (CF) (CF) 7.46 2.48 16.94 6828.59 6151.59 12.46 1.78 12.14 8074.30 7181.31 17.46 1.43 9.75 8966.05 7853.10 22.46 1.21 8.27 9661.31 8325.93 ORIFICE CALCULATIONS 27.46 1.06 7.26 10228.51 8668.95 32.46 0.95 6.51 10704.36 8919.30 MATCHING Qp: 37.46 0.87 5.93 11111.13 9099.52 (Basin H1 - D1) = 1.64 cfs 42.46 0.80 5.47 11463.50 9224.47 47.46 0.75 5.09 11771.68 9304.50 52.46 0.70 4.77 12043.13 9347.18 CIRCULAR ORIFICE: 57.46 0.66 4.49 12283.46 9358.19 DIAMETER =6.000 inches 62.46 0.62 4.26 12497.04 9341.96 Area =0.20 ft2 67.46 0.59 4.05 12687.31 9301.98 Max. Depth = 3.00 ft 72.46 0.57 3.86 12857.05 9241.10 ORIFICE FLOW = 1.64 CFS 77.46 0.54 3.70 13008.57 9161.64 82.46 0.52 3.55 13143.77 9065.52 RECTANGULAR ORIFICE: 87.46 0.50 3.42 13264.24 8954.39 LENGTH = 5.500 inches 92.46 0.48 3.30 13371.35 8829.62 WIDTH = 5.125 inches 97.46 0.47 3.19 13466.28 8692.41 Area =0.20 ft2 102.46 0.45 3.09 13550.03 8543.80 Max. Depth = 3.00 ft 107.46 0.44 2.99 13623.50 8384.68 ORIFICE FLOW = 1.63 CFS 112.46 0.43 2.90 13687.47 8215.85 117.46 0.41 2.82 13742.62 8038.00 122.46 0.40 2.75 13789.56 7851.76 127.46 0.39 2.68 13828.84 7657.69 132.46 0.38 2.61 13860.95 7456.28 137.46 0.37 2.55 13886.33 7247.98 142.46 0.36 2.49 13905.38 7033.21 147.46 0.36 2.43 13918.47 6812.32 152.46 0.35 2.38 13925.91 6585.67 POST-DEV Qp = POND VOLUME CALCULATIONS: BASIN AREA POST = POST-DEV Tc = POST-DEV C = STORM INTENSITY = Triangle Release Constant Release DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN) (IN/HR) (CFS) (CF) (CF) 157.46 0.34 2.33 13928.02 6353.55 162.46 0.33 2.29 13925.08 6116.24 167.46 0.33 2.24 13917.32 5874.01 172.46 0.32 2.20 13905.00 5627.10 177.46 0.32 2.16 13888.33 5375.73 182.46 0.31 2.12 13867.50 5120.10 187.46 0.31 2.08 13842.70 4860.40 192.46 0.30 2.05 13814.12 4596.81 197.46 0.30 2.01 13781.90 4329.49 202.46 0.29 1.98 13746.20 4058.60 207.46 0.29 1.95 13707.16 3784.28 212.46 0.28 1.92 13664.91 3506.66 217.46 0.28 1.89 13619.57 3225.88 222.46 0.27 1.86 13571.27 2942.05 227.46 0.27 1.84 13520.11 2655.28 232.46 0.27 1.81 13466.19 2365.68 237.46 0.26 1.79 13409.61 2073.35 242.46 0.26 1.76 13350.46 1778.38 247.46 0.25 1.74 13288.83 1480.86 252.46 0.25 1.72 13224.80 1180.87 257.46 0.25 1.69 13158.46 878.50 262.46 0.25 1.67 13089.86 573.81 267.46 0.24 1.65 13019.09 266.89 272.46 0.24 1.63 12946.21 -42.21 277.46 0.24 1.61 12871.28 -353.41 282.46 0.23 1.60 12794.37 -666.65 287.46 0.23 1.58 12715.53 -981.88 292.46 0.23 1.56 12634.81 -1299.04 297.46 0.23 1.54 12552.28 -1618.07 302.46 0.22 1.53 12467.97 -1938.92 307.46 0.22 1.51 12381.94 -2261.55 312.46 0.22 1.49 12294.24 -2585.90 317.46 0.22 1.48 12204.90 -2911.94 322.46 0.21 1.46 12113.97 -3239.61 327.46 0.21 1.45 12021.49 -3568.89 332.46 0.21 1.44 11927.51 -3899.71 337.46 0.21 1.42 11832.05 -4232.06 342.46 0.21 1.41 11735.15 -4565.89 347.46 0.20 1.39 11636.84 -4901.16 352.46 0.20 1.38 11537.17 -5237.85 357.46 0.20 1.37 11436.16 -5575.92 362.46 0.20 1.36 11333.84 -5915.34 367.46 0.20 1.35 11230.25 -6256.07 Bozeman Gateway - Building G Overflow Parking Lot - Site Plan Sub-Basin D1 StormTech Sizing Calculations Required Storage Volume 11,643 ft3 StormTech Modules, Model No.SC740 (30" chamber height) Depth to top of gravel 36 in. installed storage volume 68.14 ft3 per chamber (see note 1) Number of chambers required 171 170.87 before rounding excess storage volume 0.1 % Number of chambers proposed 203 excess storage volume 15.8 % equal to 1,843 ft3 excess storage volume Installed chamber footprint (per chamber) = 5' x 7.12' Storage Volume Provided = 13,486 ft3 Notes: 1. Storage volume assumes 6" of stone above and between chamber rows, and 40% stone porosity. Storage volume under the chambers is not included (assumes voids are 100% filled with sediment). Bozeman Gateway - Building G Overflow Parking Lot - Site Plan Sub-Basin D1 Peak Flows for 25 and 100-yr Storms MODIFIED RATIONAL METHOD Qp = C i A 25-YEAR PEAK RUNOFF: RAINFALL FREQ = 25 yr, 1 hr. BASIN AREA POST = 8.03 acres STORM EVENT STORM i COEFF INTENSITY (YR)A B (IN/HR) POST-DEV Tc = 7.9 min. 2 0.36 -0.60 1.22 5 0.52 -0.64 1.91 POST-DEV C = 0.85 10 0.64 -0.65 2.40 25 0.78 -0.64 2.87 STORM A = 0.78 50 0.92 -0.66 3.52 B = -0.64 100 1.01 -0.67 3.95 STORM INTENSITY = 2.87 IN/HR (Source: City of Bozeman Design Standards, March 2004) Qp =19.57 CFS 100-YEAR PEAK RUNOFF: RAINFALL FREQ = 100 yr, 1 hr. BASIN AREA POST = 8.03 acres STORM EVENT STORM i COEFF INTENSITY (YR)A B (IN/HR) POST-DEV Tc = 7.9 min. 2 0.36 -0.60 1.22 5 0.52 -0.64 1.91 POST-DEV C = 0.85 10 0.64 -0.65 2.40 25 0.78 -0.64 2.87 STORM A = 1.01 50 0.92 -0.66 3.52 B = -0.67 100 1.01 -0.67 3.95 STORM INTENSITY = 3.95 IN/HR (Source: City of Bozeman Design Standards, March 2004) Qp =26.93 CFS i = A * (Tc/60) B i = A * (Tc/60) B Culvert Calculator Report 24" discharge culvert, 25-yr Title: Kohl's Site Plan n:\...\bldg. g overflow parking\culverts.cvm 08/13/14 04:21:47 PM Morrison Maierle Inc © Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Project Engineer: Mike Hickman CulvertMaster v3.3 [03.03.00.04] Page 1 of 1 Solve For: Headwater Elevation Culvert Summary Allowable HW Elevation 44.90 ft Headwater Depth/Height 3.00 Computed Headwater Elevation 44.74 ft Discharge 19.57 cfs Inlet Control HW Elev. 43.16 ft Tailwater Elevation 43.16 ft Outlet Control HW Elev. 44.74 ft Control Type Outlet Control Grades Upstream Invert 38.73 ft Downstream Invert 38.36 ft Length 105.70 ft Constructed Slope 0.003500 ft/ft Hydraulic Profile Profile PressureProfile Depth, Downstream 4.80 ft Slope Type N/A Normal Depth N/A ft Flow Regime N/A Critical Depth 1.59 ft Velocity Downstream 6.23 ft/s Critical Slope 0.006756 ft/ft Section Section Shape Circular Mannings Coefficient 0.012 Section MaterialCorrugated HDPE (Smooth Interior) Span 2.00 ft Section Size 24 inch Rise 2.00 ft Number Sections 1 Outlet Control Properties Outlet Control HW Elev. 44.74 ft Upstream Velocity Head 0.60 ft Ke 0.50 Entrance Loss 0.30 ft Inlet Control Properties Inlet Control HW Elev. 43.16 ft Flow Control Submerged Inlet Type Square edge w/headwall Area Full 3.1 ft² K 0.00980 HDS 5 Chart 1 M 2.00000 HDS 5 Scale 1 C 0.03980 Equation Form 1 Y 0.67000