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HomeMy WebLinkAbout15 - Design Report - Cannery District PUD - Stormwater Storm Water Plan Cannery District PUD February, 2015 For Submittal to: City of Bozeman Engineering Department 20 East Olive Bozeman, MT 59715 Prepared by: Stahly Engineering and Associates 851 Bridger Drive, Suite 1 Bozeman, MT 59715 (406) 522-9526 STAH LY Ke,x1970 s�C1R'f�S Storm Water Plan Contents General Information Existing Conditions and General Design Criteria Storm Drainage Plan Description Estimation of Retention Volume Retention Facilities Curb and Gutter Capacity Inlet Capacity Facilities Maintenance Figures and Tables Figure 1. Storm Water Plan Table 1. Cumulative Retention Volume Needed by Phase Table 2. Cumulative Retention Capacity by Phase Table 3 Curb and Gutter Capacity Calculations Table 4 Inlet Drainage Basin and Pipe Capacity Calculations Storm Water Plan 1 2/5/2015 General Information The Cannery District is a multi-phase development located on the north side of East Oak Street and Rouse Avenue, north of the Gallatin County Fairgrounds. The existing property consists of several parcels of land within the City and County, with 3.30 acres within the City and 8.94 acres in the county. The development consists of four phases. The first phase, which was approved by the City of Bozeman and MDEQ in November of 2014, consists of remodeling four existing buildings originally constructed as part of the original pea canning operation in 1917. These buildings are currently served by city utilities. Though not required by the redevelopment of the existing buildings, the existing water and sewer infrastructure will be replaced and upgraded to current City standards, prior to the construction of proposed Phase 1 site improvements. A deferred annexation is being proposed with the City of Bozeman for the eventual annexation of Phase 1. Phases 2, 3 and 4 involve the construction of six new buildings on the cannery district property. The developer's contact information is: Cannery District Partners, LLC 1006 W Main Street Bozeman, MT 95715 Existing Conditions and General Design Criteria The site's existing conditions consist of four existing buildings, with the majority of the land undeveloped. The site's topography allows for drainage to the north west corner. Near the north east corner of the lot, an existing storm water detention pond is currently in use to serve the Northside PUD which consists of four buildings located at the corner of Oak and Rouse. In accordance with the City of Bozeman Design Standards and Specifications Policy(COB Standards) an engineering analysis has been conducted for all four phases within the Cannery District property. The proposed design includes storm sewers that have been sized to convey the 25 year storm event with no surcharging. The storm sewers drain towards the north west corner of the lot. Due to the presence of Interstate 90 on the northern boundary of the Cannery District property, there is no outlet for stormwater runoff. Therefore, the storm sewers end in a retention pond sized to handle a 10- year 2-hour event per COB Standards. Furthermore, storm water bioswales will be used throughout the site to further reduce surface runoff and enhance stormwater infiltration. Storm Water Plan 2 2/5/2015 Storm Drainage Plan Storm drainage improvements for the Cannery District will be constructed in accordance with City of Bozeman Requirements. Phase 1 storm drainage improvements will provide the "backbone" drainage infrastructure for future phases. Therefore a Master Grading Plan has been prepared for the Cannery District, to determine future phase's drainage requirements. The overall storm drainage plan for the Cannery District is depicted on Figure 1 at the end of this report. Overall drainage direction on the proposed development is indicated by arrows showing the proposed drainage patterns and inlet locations. An existing storm retention pond located to the north of the Northside PUD will be replaced by a stormwater collection system that will direct this water to the proposed Cannery District retention basin. Additionally, the collection system has been designed to transmit pre- development(or treated post-development) runoff from the 31.8 acre basin (part of the Gallatin County Fairgrounds) to the south of Oak Street. This would allow the Cannery District storm drainage system to be incorporated into a neighborhood system, should the City wish to partner with the Cannery District. Estimation of Retention Volume Runoff estimates were obtained for each phase using a 1 0-year 2-hour design storm. The Bozeman IDF curves show a rainfall intensity of 0.41 in/hour for the 1 0-year 2-hour design storm. Using a runoff coefficient of 0.8 (Commercial Downtown), and the accumulative area by phase, it was determined that a 10- year 2-hour retention volume of 38,859 d will be required. Table 1 — Cumulative Retention Volume Needed by Phase 1 0-year 2-hour event Phase 1 Phase 2 Phase 3 Phase 4 weighted C Factor C 0.8 0.8 0.8 0.8 Intensity I in/hr 0.41 0.41 0.41 0.41 Area A acres 5.34 8.30 14.63 16.45 Runoff Q cfs 1.75 2.72 4.80 5.40 Retention Volume V cf 12,614 19,594 34,557 38,859 NOTE: Phase 3 includes Northside PUD Storm Water Plan 3 2/5/2015 Retention Facilities To accommodate the required retention volume the Cannery District Phase 1 system will include the construction of bioswales and retention basins that have a combined capacity of 40,054 CF, enough volume to handle all four phases. However, to achieve Low Impact Design, additional bioswales in future phases will add retention volume, providing more capacity than is required by just the 10- year 2-hour event. The main retention basin is located on the northwest (down gradient) corner of the site, bordering the interstate right of way. It will have slopes of 4:1, a maximum water depth of 2 ft, and be vegetated with grass. Initially, the retention basin will be constructed with a volume of 32,736 cubic feet. This basin will be in place until Phase 4. Phase 4 has two scenarios, both of which will provide adequate retainage volume. The first is to keep the initial retention basin as part of the final design, and the second is to replace a portion of the retention basin with below ground stormwater retention chambers in order to provide more parking spaces. This determination will be made at a later date depending on parking needs. The bioswales will have a 12" depth below the overflow outlet, and consist of 24" of bioswale media (mixture of sand, topsoil, and compost)topped with vegetation per the landscape plans. Bioswale capacities were calculated using a 0.35 void ratio. The volume provided by each phase of construction is as follows: Table 2 — Cumulative Retention Capacity by Phase Phase Volume(cf) Notes 1 40,054 Initial retention basin/bioswales 2 43,862 Initial retention basin/added bioswales 3 49,972 Initial retention basin/added bioswales 4 49,972 Initial retention basin/added bioswales,or Reconstruction with retention basin/bioswales and below 4 50,845 parking storage Storm Water Plan 4 2/5/2015 Curb and Gutter Capacitv Storm runoff will be collected in street and parking lot curb and gutters. The hydraulic capacity of the curb and gutter was analyzed to determine if the curb would be overtopped in a 25-year event. The maximum 25-year event for any of the new curb inlet basins produces approximately 3.74 cfs of runoff. The capacity of the curb at the lowest designed slope of 0.5% is 5.03 cfs at a depth of 0.15 feet below the top of the curb. Therefore, curb capacities in the development are adequate to carry the 25-year event. Table 3 — Curb and Gutter Capacity Calculations Right-side slope X:1 0.05 Left-side slope X:1 33.00 Channel bottom width(ft) 0 Flow Depth (ft) 0.350 Flow Area(ft^2) 2.024 Wetted Perimeter(ft) 11.906 Width 0.035 Hydraulic Radius(ft) 0.170 Manning's Roughness 0.013 Slope(ft/ft) 0.005 Average Velocity(ft/sec) 2.49 Flow(ft^3/sec) 5.03 Inlet and Area Drain Capacitv The curb inlets and area drains on the roadways in the development were analyzed to ensure they have capacity to accept flows conveyed to them without reaching a point 0.15 feet from the top of the curb. The COB approved Neenah Foundry R-3067-L inlet structure has a capacity of 5.98 cfs at 0.35 feet of head (0.15 below top of curb). The COB approved Neenah Foundry R-2533 area drain has a capacity of 3.2 cfs at 0.45 feet of head (0.15 feet below top of lowest adjacent curb). These capacities will convey the necessary flows. Facilities Maintenance The proposed storm drainage facilities will be operated and maintained by the property owners' association (POA). The POA is responsible for quarterly maintenance of all storm water facilities. The maintenance includes, but is not limited to, visual inspection and removal of sediment from curbs, inlets, retention basins, and outlet structures as well as any necessary repairs to the facilities. Storm Water Plan 5 2/5/2015 Table 4 Inlet Drainage Basin and Pipe Capacity Calculations(All Phases) Inlet Drainage Basin Inlet Basin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Off Site Land Use M-1 M-1 M-1 M-I M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 M-1 Drainage Area(acres) 0.65 0.34 1.24 0.67 0.40 1.32 1.00 0.94 0.53 0.43 0.19 0.23 0.55 0.36 1.13 0.19 1.21 0.24 0.56 106 0.29 31.80 Sloe % 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Runoff Coefficients 0.8 0.8 0.8 0.8 0.8 0.8 0.6 0.8 0.8 0.6 0.8 0.8 0.8 0.6 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.2 Frequency Adjustment Factor,Cf 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 Basin Length ft 205 146 478 254 135 246 255 161 176 231 99 133 153 148 222 109 232 102 170.5 365 150 900 Time of Concentration min 5A 4.4 7.9 5.7 4.2 5.6 5.7 4.8 4.8 5.5 3.6 4.1 4.4 4.4 5.4 3.8 5.5 3.6 4.7 6.9 4.4 43.1 Peak Flow Calculations Design Storm 25 r 25 r 25 r 25 r 25 r 25 r 25 r I 25 r I 25 r I 25 r I 25 r I 25 r 25 r I 25 r I 25 r I 25 r 25 r 25 r j5r 25 r 25 rIntensit at Tc Fi ure 1-2 .29 in/hr 3.76 4.17 287 351 4.29 3.54 3.50 3,91 3.93 3.62 4.74 4.31 4.13 4.17 3.66 4.60 3.61 4.70 3.12 .15Peak Runoff Rate at Tc(O=CIA (cfs) 1.95 1.13 2.84 1.88 1.37 3.74 2,80 2.94 1.67 1,24 0.72 0.79 1.82 1.20 3.31 0.70 3.50 0.90 7.65 0.96 1 6.13 Storm Drain Pipe A Capacity Manhole Number Pipe End ST1A ST2A ST3A ST41A ST5A ST6A ST7A ST8A PI a End Rim Elev 4747.03 4749.51 4749.88 4749.25 4750.39 4750.95 4750.13 4751.20 Invert 1 4742.25 4742.89 4745.29 4746.39 4745.78 4746.07 4747.26 4747.38 4746.36 4748.28 Invert 2 4746.04 4746.82 Pie Number 1A 2A 3A 4A 5A 6A 7A BA 9A Pipe Size in 24.00 24.00 15.00 24.00 24.00 15.00 15.00 24.00 24.00 Pipe Length 47.00 W26.554.58 .36 122.76 71.94 108.88 30.84 72.55 25.46 Mannin 's"n" PVC 0.013013 0.013 0.013 0.013 0.013 0.013 0.013 Area(j,2) 3.14 ,23 3.14 3.14 1.23 1.23 3.14 3.14 Welled Perimeter 11 6.28 .93 6.28 6.28 3.93 3.93 6.29 6.23 Hydraulic Radius 11 0.50 .31 0.50 0.50 0.31 0.31 0.50 0.50 Slope fufl 0.0137 050 0.0040 0.0040 0.0040 0,0040 0.0040 0.0400 Full Flow Capacity cfs 26.55 .58 14.35 14.35 4.10 4.10 14.35 45.37 Velocit fusee 8.45 .73 4.57 4,57 3.34 3.34 4.57 14.44 Contributin Inlet Basin NONE2 5 NONE NONE 8 NONE 3 OFF SFE ContributingPipes 2A 3A NONE SA 6A 7A NONE 9A 4A BA Actual Pipe Flow(CIS) 17.22 17.22 1.13. 13.28 11.91 2.94 2.94 8.97 8.97 Capacity 65% 65% 25% 93% 83% 721/. 72% 63% 20% Storm Drain Pipe B Capacity Manhole Number Pipe End ST!B ST2B ST3B SUB ST5B STGB ST713 STBB ST9B Rim Elev 4748.23 4746.00 4748.22 4749.65 4749.30 4749.81 4749.81 4750.17 4751.20 Invert 4742.25 4743.24 4745.00 4743.40 4744.18 4745.02 4745.17 4746.05 4746.78 4748.06 Invert 2 4744.49 4743.90 4744.93 4745.67 4747.03 Invert 3 4745.92 Pie Number 1B 2B 38 4B 5B 6B 7B BB 913 Pipe Size in 30.00 15.00 30.00 24.00 15.00 24.00 15.00 18.00 15.00 Pipe Length 198.17 1 51.01 31.83 69.66 1 18.39 248.42 25.00 103.45 75.00 Mannin 's"n" PVC 0.013 0.013 0.013 0.013 1 0.013 0.013 0.013 0.013 0.013 Area Its 4.91 1.23 4.91 3.14 1.23 3.14 1.23 1.77 1.23 Welled Perimeter ft 7.85 3.93 7.85 6.28 3.93 6.28 3.93 4.71 3.93 Hydraulic Radius 11 0.63 0.31 0.63 0.50 0.31 0.50 0.31 0.38 0.31 Sloe full 0.0050 0.0100 0.0050 0,0040 0.0050 0.0040 0.0050 0,0106 0.0137 Full Flow Capacity cfs 29.08 6.48 29.08 14.35 4.58 14.35 4.58 10.92 7.58 Velocity(fusee) 5.92 5.28 5.92 4.57 3.73 4.57 3.73 6.18 6.18 Contribulin Inlet Basm NONE 9 11 12 17 13 10 14 15 Contribulin Pi es 28 NONE 4B INONE 78 ONE 96 NONE 3B 1C 6B BB Actual Pipe Flow(cls) 26.24 1.67 24.57 11.86 3.50 7.57 1.24 4.51 3.31 %Capacity 90% 26% 85% 83% 76% 53% 27% 411/. 44% Storm Drain Pipe C Capacity Manhole Number ST38 ST1C ST2C ST3C ST4C End Pipe EXISTING Rim Elev 4749.23 4750.40 4751,42 Invert 4743.90 4744.92 4746.09 4747.62 4747.56 4747.90 Invert 2 4746.59 4747.81 Invert 3 4746.84 Pie Number 1c 2C 3C 4C 5C Pipe Size in 24.00 1 24.00 15.00 18.00 1 15.00 Pipe Length 145.59 167.98 110.56 137.31 23.99 Mannin's"n" PVC 0.013 0.013 0.013 0.013 0.013 Area fl' 3.14 3.14 1.23 1.77 1.23 Welled Perimeter ft 6.28 6,28 3.93 4.71 3.93 Hydraulic Radius 11 0.50 0.50 0.31 0.38 0.31 Slope Iufl 0.0070 0.0070 0.0070 0.0070 0.0040 Full Flow Capacity cfs 18.98 18.98 5.42 8.81 4.10 Velocity f./sec 6.04 6.04 1 4.42 4.99 3.34 Contributing Inlet Basin 16 18 19 21 20 ContributingPipes 2C 3C NONE SC NONE 4C Actual Pipe Flow(cfs) 11.99 1 11.30 1.79 8.61 1 7.65 %Capacity 63% 60% 33% 98% 167% 1 Comma-CI1' Architecture.Inc. 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