HomeMy WebLinkAboutAppendix 3 - Storm Water Plan
Cannery District Planned Unit Development
Preliminary PUD Application
Cannery District Partners, llc
Appendix 3
Storm Water Plan
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
Storm Water Plan 1 2/5/2015
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 2 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 3 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 10-year 2-hour design
storm. The Bozeman IDF curves show a rainfall intensity of 0.41 in/hour for the
10-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 cf will be required.
Table 1 – Cumulative Retention Volume Needed by Phase
10-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 4 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
4 50,845
Reconstruction with retention basin/bioswales and below
parking storage
Storm Water Plan 5 2/5/2015
Curb and Gutter Capacity
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 Capacity 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.
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-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I M-I
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 3.06 0.29 31.80
Slope (%)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 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 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) 205 148 478 254 135 246 255 181 178 231 99 133 153 148 222 109 232 102 170.5 365 150 900
Time of Concentration (min) 5.1 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 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr 25yr
Intensity at Tc (Figure I-2 pg. 29) (in/hr) 3.76 4.17 2.87 3.51 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 3.98 3.12 4.15 0.96
Peak Runoff Rate at Tc (Q = 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 1.79 7.65 0.96 6.13
Storm Drain Pipe A Capacity
Manhole Number Pipe End ST1A ST2A ST3A ST4A ST5A ST6A ST7A ST8A Pipe 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
Pipe Number 1A 2A 3A 4A 5A 6A 7A 8A 9A
Pipe Size (in)24.00 24.00 15.00 24.00 24.00 15.00 15.00 24.00 24.00
Pipe Length 47.00 175.14 68.36 122.76 71.94 108.88 30.84 72.55 25.46
Manning's "n" (PVC)0.013 0.013 0.013 0.013 0.013 0.013 0.013 0.013 0.013
Area (ft2)3.14 3.14 1.23 3.14 3.14 1.23 1.23 3.14 3.14
Wetted Perimeter (ft)6.28 6.28 3.93 6.28 6.28 3.93 3.93 6.28 6.28
Hydraulic Radius (ft)0.50 0.50 0.31 0.50 0.50 0.31 0.31 0.50 0.50
Slope (ft/ft)0.0137 0.0137 0.0050 0.0040 0.0040 0.0040 0.0040 0.0040 0.0400
Full Flow Capacity (cfs) 26.55 26.55 4.58 14.35 14.35 4.10 4.10 14.35 45.37
Velocity (ft/sec)8.45 8.45 3.73 4.57 4.57 3.34 3.34 4.57 14.44
Contributing Inlet Basin NONE 7 2 5 NONE NONE 8 NONE 3
OFF SITE
Contributing Pipes 2A 3A NONE 5A 6A 7A NONE 9A
4A 8A
Actual Pipe Flow (cfs)17.22 17.22 1.13 13.28 11.91 2.94 2.94 8.97 8.97
% Capacity 65% 65% 25% 93% 83% 72% 72% 63% 20%
Storm Drain Pipe B Capacity
Manhole Number Pipe End ST1B ST2B ST3B ST4B ST5B ST6B ST7B ST8B ST9B
Rim Elev 4748.23 4748.00 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
Pipe Number 1B 2B 3B 4B 5B 6B 7B 8B 9B
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 51.01 31.83 69.66 18.39 248.42 25.00 103.45 75.00
Manning's "n" (PVC)0.013 0.013 0.013 0.013 0.013 0.013 0.013 0.013 0.013
Area (ft2)4.91 1.23 4.91 3.14 1.23 3.14 1.23 1.77 1.23
Wetted Perimeter (ft)7.85 3.93 7.85 6.28 3.93 6.28 3.93 4.71 3.93
Hydraulic Radius (ft)0.63 0.31 0.63 0.50 0.31 0.50 0.31 0.38 0.31
Slope (ft/ft)0.0050 0.0100 0.0050 0.0040 0.0050 0.0040 0.0050 0.0108 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 (ft/sec)5.92 5.28 5.92 4.57 3.73 4.57 3.73 6.18 6.18
Contributing Inlet Basin NONE 9 11 12 17 13 10 14 15
Contributing Pipes 2B NONE 4B 5B NONE 7B NONE 9B NONE
3B 1C 6B 8B
Actual Pipe Flow (cfs)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% 41% 44%
Storm Drain Pipe C Capacity
Manhole Number ST3B 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
Pipe Number 1C 2C 3C 4C 5C
Pipe Size (in)24.00 24.00 15.00 18.00 15.00
Pipe Length 145.59 167.98 110.56 137.31 23.99
Manning's "n" (PVC)0.013 0.013 0.013 0.013 0.013
Area (ft2)3.14 3.14 1.23 1.77 1.23
Wetted Perimeter (ft)6.28 6.28 3.93 4.71 3.93
Hydraulic Radius (ft)0.50 0.50 0.31 0.38 0.31
Slope (ft/ft)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 (ft/sec)6.04 6.04 4.42 4.99 3.34
Contributing Inlet Basin 16 18 19 21 20
Contributing Pipes 2C 3C NONE 5C NONE
4C
Actual Pipe Flow (cfs)11.99 11.30 1.79 8.61 7.65
% Capacity 63% 60% 33% 98% 187%