Environmental Design Group

Transcription

1 SEDIMENT CONTROL DURING CONSTRUCTION, STORMWATER MANAGEMENT AND POST CONSTRUCTION BMP REPORT for Hudson Salt Storage and Bus Garage 5810 Hudson Drive HUDSON, OHIO SUMMIT COUNTY Prepared by Environmental Design Group The community impact people. Revised: April 3, 2017

2 I INTRODUCTION This project involves the construction of bus parking and maintenance facility as well as a salt storage facility in southern Hudson, Ohio. An aerial view of the project site is provided in Attachment A. This report details sediment control during construction, stormwater management, and post construction Best Management Practices for the proposed improvements. II EXISTING CONDITIONS The current site consists of open and wooded areas with an existing gravel driveway and stockpile area. A delineation of wetlands and other waters has been performed of the site and four wetland types, one ephemeral stream and three intermittent streams have been identified. The wetlands account for roughly 50% of the site while the streams combined length is approximately 2,000 linear feet. See Attachment A & B for drainage maps, hydrographs and flow information. The project site also receives run-off from the property to the north. The northern parcel has a detention basin which discharges its treated stormwater toward the project site. The soils for the property are mostly Type D soils, but a small northwest portion of the site is Type B. The point of analysis for the preconstruction conditions is the southwest corner of the site. III PROPOSED CONDITIONS The City of Hudson and the Hudson City Schools have collaborated on the future Hudson Salt Storage and Bus Garage. The site will accommodate the storage facility for the City s road salt and staff members as well as the School District s bus maintenance garage, parking for the bus fleet, and parking lot for the bus drivers and maintenance personnel. Although the parcel is roughly 40 acres the facilities will impact roughly 8.9 acres and the improvements increase the imperviousness of the site by roughly 46.50%. Great consideration of site City s needs and the site s sensitive environmental nature dictated the layout of the site. The central linear driveway leads to the salt storage building and bus garage that have moved closest to the site frontage to minimize environmental impacts. Parking has been minimized and utilities will be shared to reduce construction disturbances. Two centralized stormwater treatment basins with pretreatment BMP are strategically placed to effectively treat stormwater per the EPA and City s standards. They are designed per the ODNR Rainwater and Land Develop Manual and will treat stormwater to meet the EPA NPDES permit requirements and Pre/Post peak flow requirements per the City of Hudson s standards. In an effort to mimic the predeveloped hydrologic conditions of the offsite run-off from the north the stormwater will be captured in swales, directed to storm structures then bypassed around the site.

3 The captured flow will leave the study area at the same point of analysis in the pre-developed state by way of a level spreader which will convert the pipe flow back to sheet flow, extend the time of concentration and allow for additional opportunity for settlement of solids. Drainage for the site will be divided into two separate areas, the salt storage facility and entry drive in one area and the school bus maintenance and parking facility as well as the associated staff parking in another. The majority of the run-off generated from the salt storage area will be treated in a dry detention basin, equipped with a forebay and micropool, prior to release from the site at the required predeveloped rates. This facility was selected due to its ability to detain and treat stormwater. The strategic placement of the forebay close to the drive was intentional with the understanding that the salt storage facility would likely have high silts and salt in the first flush run-off and need more frequent maintenance. Run-off from the school bus parking area will sheet flow to a linear bioretention cell and the remainder of the bus maintenance facility and associated parking will be piped to a detention basin for treatment and detention prior to release at the critical storm predeveloped rates. The bioretention cell is right sized for water quality treatment of the bus parking area and lags the flow to the detention basin to assist in reducing the peak flows and basin size. Again, a thoughtful process of stormwater treatment and facility maintenance dictated design. See Attachment C for drainage maps, hydrographs and flow information. IV SEDIMENT CONTROL DURING CONSTRUCTION Elements of this project affecting water quality during construction include clearing trees and vegetation, earth moving, grading for surface water drainage, constructing the building structures and surface parking. Silt fence, inlet protection, sediment basin and a construction drive will also be used to control sediment during construction. Final restoration will be performed after finish grading and top soiling have been completed. V STORMWATER MANAGEMENT METHODOLOGIES The USDA Soil Conservation Service (SCS) TR-20 methodology (as described in the SCS National Engineering Handbook, Section 4, Hydrology NEH-4) was used to model the hydrology for the detention/water quality basin designs. These methodologies are incorporated into the computer application HydroCAD. The rainfall intensity values used in the stormwater runoff control calculations, listed in Table 1, were obtained from NOAA s Precipitation Frequency Data Server.

4 Table 1. Rainfall Frequency Data Storm Event Years 24-Hour Rain Event VI DETAINED STORM The City of Hudson s stormwater management regulations require the peak discharge shall be controlled by reducing the 25-year post developed peak discharge to the 2-year predeveloped peak discharge over the same area. The City also requires that the smallest orifice diameter to be 4 inches. The East and West detentions basins have been designed to meet the City s design criteria. The pre-development and post-development stormwater management calculations and drainage maps are located in Attachments B & C. A summary of the peak flows for the pre- and postdeveloped conditions are shown in Table 2, below. Table 2. Summary of Peak Flows (cfs) Storm Events Drainage Area 1-YR 2-YR 5-YR 10-YR 25-YR 50-YR 100-YR Predevelopment Entire site Post Development East detention basin West detention basin Combined Hydrographs VII WATER QUALITY Per Ohio EPA s General Permit OCH000004, post construction Best Management Practices must be installed to treat the first flush of any storm event. The water quality volume (WQv) runoff from the bus parking and maintenance facility will be treated utilizing a bioretention cell and dry detention basin. A separate detention basin will be installed to treat the water quality volume for the salt storage facility. The water quality volume (WQv) drainage maps and calculations are included in Attachment D.

5 Following completion of the project and release of the contractor, the best management practices will be maintained by Hudson City Schools and the City of Hudson.

6 ATTACHMENT A AERIAL MAP OF PROJECT SITE

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8 ATTACHMENT B PREDEVELOPMENT STORMWATER MAPS AND CALCULATIONS

9 GRAPHIC SCALE Although three drainage area are represented on the map the entire impact area drains northeast to southwest. Therefore the southwest corner is the point of analysis for the entire site. HUDSON KOBERNA PROPERTY 5810 HUDSON DRIVE Hudson, Ohio PRE DEVELOPED DRAINAGE MAP

10 CALCS Type II 24-hr 25 YR Rainfall=4.24" Prepared by {enter your company name here} Printed 4/3/2017 HydroCAD s/n HydroCAD Software Solutions LLC Page 1 Summary for Subcatchment 5S: Whole Site (Pre) Runoff = hrs, Volume= af, Depth= 2.41" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.05 hrs Type II 24-hr 25 YR Rainfall=4.24" Area (ac) CN Description Paved parking, HSG D Woods/grass comb., Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Woods: Light underbrush n= P2= 2.44" Shallow Concentrated Flow, Woodland Kv= 5.0 fps Total Subcatchment 5S: Whole Site (Pre) Hydrograph cfs Type II 24-hr 25 YR Rainfall=4.24" Runoff Area=8.930 ac Runoff Volume=1.793 af Runoff Depth=2.41" Flow Length=870' Tc=59.9 min CN=82 Runoff Time (hours)

11 CALCS Type II 24-hr 100 YR Rainfall=5.48" Prepared by {enter your company name here} Printed 4/3/2017 HydroCAD s/n HydroCAD Software Solutions LLC Event Runoff (cfs) Events for Subcatchment 5S: Whole Site (Pre) Volume (acre-feet) Depth (inches) 1 YR YR YR YR YR YR YR

12 ATTACHMENT C POST DEVELOPMENT STORMWATER MAPS AND CALCULATIONS

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14 CALCS Type II 24-hr 25 YR Rainfall=4.24" Prepared by {enter your company name here} Printed 4/3/2017 HydroCAD s/n HydroCAD Software Solutions LLC Page 5 Summary for Pond 7P: East Detention Basin Inflow Area = ac, 55.07% Impervious, Inflow Depth = 3.15" for 25 YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 89%, Lag= 28.9 min Primary = hrs, Volume= af Secondary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.05 hrs / 2 Peak Elev= hrs Surf.Area= 9,272 sf Storage= 14,435 cf Plug-Flow detention time= min calculated for af (100% of inflow) Center-of-Mass det. time= min ( 1, ) Volume Invert Avail.Storage Storage Description #1 1,069.00' 47,629 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 1, , ,106 1, , ,954 4,954 8,049 1, , ,572 12,526 9,127 1, , ,969 23,495 20,522 1, , ,416 38,910 21,036 1, , ,719 47,629 21,293 Device Routing Invert Outlet Devices #1 Primary 1,069.00' 12.0" Round Culvert L= 50.0' RCP, square edge headwall, Ke= Inlet / Outlet Invert= 1,069.00' / 1,068.50' S= '/' Cc= n= 0.013, Flow Area= 0.79 sf #2 Device 1 1,069.00' 4.0" Vert. Orifice/Grate C= #3 Device 1 1,070.50' 6.0" Vert. Orifice/Grate C= #4 Device 1 1,071.50' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) Width (feet) #5 Device 1 1,072.35' 2.0" x 23.0" Horiz. Orifice/Grate X 8 rows C= in 24.0" x 24.0" Grate (64% open area) Limited to weir flow at low heads #6 Secondary 1,072.00' 10.0' long x 8.0' breadth Broad-Crested Rectangular Weir Head (feet) Coef. (English)

15 CALCS Type II 24-hr 25 YR Rainfall=4.24" Prepared by {enter your company name here} Printed 4/3/2017 HydroCAD s/n HydroCAD Software Solutions LLC Page 6 Primary OutFlow Max= hrs HW=1,071.22' (Free Discharge) 1=Culvert (Passes 1.25 cfs of 4.72 cfs potential flow) 2=Orifice/Grate (Orifice Controls fps) 3=Orifice/Grate (Orifice Controls fps) 4=Custom Weir/Orifice ( Controls 0.00 cfs) 5=Orifice/Grate ( Controls 0.00 cfs) Secondary OutFlow Max= hrs HW=1,069.00' (Free Discharge) 6=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Pond 7P: East Detention Basin Hydrograph cfs Inflow Area=2.535 ac Peak Elev=1,071.22' Storage=14,435 cf Inflow Outflow Primary Secondary cfs 1.25 cfs cfs Time (hours)

16 CALCS Type II 24-hr 25 YR Rainfall=4.24" Prepared by {enter your company name here} Printed 4/3/2017 HydroCAD s/n HydroCAD Software Solutions LLC Page 7 Summary for Pond 8P: West Detention Basin Inflow Area = ac, 78.81% Impervious, Inflow Depth = 3.54" for 25 YR event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 89%, Lag= 27.5 min Primary = hrs, Volume= af Secondary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.05 hrs / 2 Peak Elev= hrs Surf.Area= 14,587 sf Storage= 34,092 cf Plug-Flow detention time= min calculated for af (100% of inflow) Center-of-Mass det. time= min ( 1, ) Volume Invert Avail.Storage Storage Description #1 1,064.00' 69,237 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 1, , , ,910 7,909 7,909 1, ,231 12,571 20,479 1, ,617 13,924 34,403 1, ,038 15,328 49,731 1, ,975 19,507 69,237 Device Routing Invert Outlet Devices #1 Primary 1,064.00' 12.0" Round Culvert L= 40.0' RCP, sq.cut end projecting, Ke= Inlet / Outlet Invert= 1,064.00' / 1,063.60' S= '/' Cc= n= 0.013, Flow Area= 0.79 sf #2 Device 1 1,064.00' 4.0" Vert. Orifice/Grate C= #3 Device 1 1,065.75' 6.0" Vert. Orifice/Grate C= #4 Device 1 1,066.75' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) Width (feet) #5 Device 1 1,068.25' 2.0" x 23.0" Horiz. Orifice/Grate X 8 rows C= in 24.0" x 24.0" Grate (64% open area) Limited to weir flow at low heads #6 Secondary 1,068.50' 10.0' long x 7.0' breadth Broad-Crested Rectangular Weir Head (feet) Coef. (English)

17 CALCS Type II 24-hr 25 YR Rainfall=4.24" Prepared by {enter your company name here} Printed 4/3/2017 HydroCAD s/n HydroCAD Software Solutions LLC Page 8 Primary OutFlow Max= hrs HW=1,066.98' (Free Discharge) 1=Culvert (Passes 2.71 cfs of 5.85 cfs potential flow) 2=Orifice/Grate (Orifice Controls fps) 3=Orifice/Grate (Orifice Controls fps) 4=Custom Weir/Orifice (Weir Controls fps) 5=Orifice/Grate ( Controls 0.00 cfs) Secondary OutFlow Max= hrs HW=1,064.00' (Free Discharge) 6=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Pond 8P: West Detention Basin Hydrograph cfs Inflow Area=4.894 ac Peak Elev=1,066.98' Storage=34,092 cf Inflow Outflow Primary Secondary cfs 2.72 cfs cfs Time (hours)

18 CALCS Type II 24-hr 25 YR Rainfall=4.24" Prepared by {enter your company name here} Printed 4/3/2017 HydroCAD s/n HydroCAD Software Solutions LLC Page 11 Summary for Link 16L: Combined Hydrographs Inflow Area = ac, 70.71% Impervious, Inflow Depth > 3.40" for 25 YR event Inflow = hrs, Volume= af Primary = hrs, Volume= af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= hrs, dt= 0.05 hrs Link 16L: Combined Hydrographs Hydrograph cfs 3.97 cfs Inflow Area=7.429 ac Inflow Primary Time (hours)

19 CALCS Type II 24-hr 100 YR Rainfall=5.48" Prepared by {enter your company name here} Printed 4/3/2017 HydroCAD s/n HydroCAD Software Solutions LLC Event Inflow (cfs) Primary (cfs) Events for Link 16L: Combined Hydrographs Elevation (feet) 1 YR YR YR YR YR YR YR

20 ATTACHMENT D STORM WATER QUALITY & DITCH CALCULATIONS

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22 Parabolic Channel for Bypass Flows Friction Method Solve For Manning Formula Discharge Roughness Coefficient Channel Slope Constructed Depth Normal Depth Constructed Top Width ft/ft 1.00 ft 1.00 ft 5.00 ft Discharge Flow Area Wetted Perimeter Hydraulic Radius Top Width Critical Depth Critical Slope Velocity Velocity Head Specific Energy Froude Number ft 3 /s 3.33 ft ft 0.61 ft 5.00 ft 0.88 ft ft/ft 3.55 ft/s 0.20 ft 1.20 ft 0.77 Flow Type Subcritical Downstream Depth Length Number Of Steps 0.00 ft 0.00 ft 0 Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Downstream Velocity Upstream Velocity Infinity Infinity ft/s ft/s Normal Depth Critical Depth Channel Slope Critical Slope 1.00 ft 0.88 ft ft/ft ft/ft 12/19/ :36:09 PM Bentley Systems, Inc. Haestad Methods SoBll:ittllliEMwMaster VSi (SELECTseries 1) [ ] 27 Siemens Company Drive Suite 200 W Watertown, CT USA Page 1 of 1

23 Date 12/2/2016 By EDG WATER QUALITY VOLUME Project Drainage Area HUDSON SALT STORAGE (CITY) Acres % Impervious Area ACRE i = 55 % WQV = C * A * P C = * i * i * i C = P = 0.75 inches WQV = Acre-inches WQV = Acre-feet Forebay Volume = 20% * WQV Vfb = Acre-feet Total Volume Require Total = Acre-feet Cubic feet Project HUDSON SALT STORAGE (SCHOOL) Detention Basin Drainage Area Acres % Impervious Area ACRE i = 78 % WQV = C * A * P C = * i * i * i C = P = 0.75 inches WQV = Acre-inches WQV = Acre-feet Forebay Volume = 20% * WQV Vfb = Acre-feet Total Volume Require Total = Acre-feet Cubic feet Project HUDSON SALT STORAGE (SCHOOL)Bioswale Drainage Area Acres % Impervious Area ACRE i = 82 % WQV = C * A * P C = * i * i * i C = P = 1.75 inches WQV = Acre-inches WQV = Acre-feet Forebay Volume = 20% * WQV Vfb = Acre-feet Total Volume Require Total = Acre-feet Cubic feet