Coal Combustion Residuals Unit Inflow Design Flood Control System Plan

Transcription

1 Coal Combustion Residuals Unit Inflow Design Flood Control System Plan Virginia Electric and Power Company Chesterfield Power Station Upper (East) Pond Chesterfield County, Virginia GAI Project Number: C October 2016 Prepared by: GAI Consultants, Inc. Richmond Office 4198 Cox Road, Suite 114 Glen Allen, Virginia Prepared for: Virginia Electric and Power Company 5000 Dominion Boulevard Glen Allen, Virginia 23060

2 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia Page i Table of Contents 1.0 Introduction Purpose Initial Inflow Design Flood Control System Plan Site Configuration Flow Into the Upper (East) Pond Flow From the Upper (East) Pond Surface Water Requirements Conclusion References... 6 Table 1 Table 2 Drawing Summary of Channel Geometries and Capacities Summary of Culvert Properties and Capacities E1-114 Plan View Existing Conditions Appendix A Hydrologic and Hydraulic Assessment 2016 GAI Consultants C / October 2016

3 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia Page 1 Certification/Statement of Professional Opinion The Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan (Plan) for the Chesterfield Power Station Upper (East) Pond was prepared by GAI Consultants, Inc. (GAI). The Plan was based on certain information that, other than for information GAI originally prepared, GAI has relied on but not independently verified. This Certification/Statement of Professional Opinion is therefore limited to the information available to GAI at the time the Plan was written. On the basis of and subject to the foregoing, it is my professional opinion as a Professional Engineer licensed in the Commonwealth of Virginia that the Plan has been prepared in accordance with good and accepted engineering practices as exercised by other engineers practicing in the same discipline(s), under similar circumstances, at the same time, and in the same locale. It is my professional opinion that the Plan was prepared consistent with the requirements of (c) of the United States Environmental Protection Agency s Standards for the Disposal of Coal Combustion Residuals in Landfills and Surface Impoundments, published in the Federal Register on April 17, 2015 with an effective date of October 19, 2015 (40 CFR 257 Subpart D). The use of the words certification and/or certify in this document shall be interpreted and construed as a Statement of Professional Opinion and is not and shall not be interpreted or construed as a guarantee, warranty or legal opinion. GAI Consultants, Inc. Kevin M. Bortz, P.E. Assistant Engineering Manager Date C / October 2016

4 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia Page 2 Acronyms CCR CCR Rule CFR DEQ Dominion EPA GAI H&H IDFCS Plan Station UEP VPDES VPDES Permit Coal Combustion Residuals Standards for the Disposal of Coal Combustion Residuals in Landfills and Surface Impoundments, 40 CFR 257 Subpart D (2015) Code of Federal Regulations Virginia Department of Environmental Quality Virginia Electric and Power Company d/b/a Dominion United States Environmental Protection Agency GAI Consultants, Inc. Hydrologic and Hydraulic Inflow Design Flood Control System CCR Unit Inflow Design Flood Control System Plan Dominion Chesterfield Power Station Upper (East) Pond Virginia Pollutant Discharge Elimination System Virginia Pollutant Discharge Elimination System Permit No. VA C / October 2016

5 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia Page Introduction The Chesterfield Power Station (Station) is owned by Virginia Electric and Power Company d/b/a Dominion Virginia Power (Dominion) and is located in Chesterfield, VA. The Station includes the Upper (East) Pond (UEP) impoundment, which is used for the long term storage of coal combustion residuals (CCR). The UEP is located on Dominion property at the Chesterfield Power Station in Chesterfield County, Virginia (coordinates 37 o North and 77 o West) and is bounded by the Old Channel of the James River on the south, Henricus Historical Park on the east, and Aiken Swamp on the north. The UEP is regulated as an existing CCR surface impoundment under the Environmental Protection Agency s Standards for the Disposal of Coal Combustion Residuals in Landfills and Surface Impoundments [40 CFR 257 Subpart D] published in the Federal Register on April 17, 2015 with an effective date of October 19, 2015 (CCR Rule). The UEP is currently regulated by Virginia Department of Environmental Quality (DEQ) Virginia Pollutant Discharge Elimination System Permit No. VA (VPDES Permit). 2.0 Purpose This CCR Unit Inflow Design Flood Control System Plan (Plan) is prepared pursuant to (c) of the CCR Rule [40 CFR (c)]. 3.0 Initial Inflow Design Flood Control System Plan In accordance with (a)(2), an initial Hazard Potential Classification was prepared for the UEP under current conditions. The UEP was determined to be a significant hazard potential CCR impoundment (GAI Consultants, 2016). As required by (a)(3), the inflow design flood for a significant hazard potential CCR surface impoundment is a 1,000-year flood. As required by (c)(1), this Plan includes: Documentation of how the inflow design flood control system (IDFCS) has been designed, constructed, operated, and maintained to adequately manage flow into the UEP during and following the peak discharge of the inflow design flood [ (a)(1)]; Documentation of how the IDFCS has been designed, constructed, operated, and maintained to adequately manage flow from the UEP so as to collect and control the peak discharge resulting from the inflow design flood [ (a)(2)]; and Documentation of how the IDFCS has been designed, constructed, operated, and maintained to adequately address the requirements of [ (b)]. 3.1 Site Configuration The UEP consists of earthen embankments and stored CCR contained within the embankments. Perimeter channels convey stormwater runoff to a stormwater sediment pond situated at the east end of the UEP. The stormwater sediment pond discharges through VPDES Permit Outfall 005. Drawing E1-114 depicts existing conditions at the UEP. 3.2 Flow Into the Upper (East) Pond The UEP embankment crest is at approximate elevation 41 at its lowest point, and the crest ranges from three feet to 35 feet above the approximate surrounding ground elevation. As such, there is no stormwater flow into the UEP and no need for a corresponding control system. The criteria established in (a)(1) are therefore met. C / October 2016

6 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia Page Flow From the Upper (East) Pond Interior perimeter channels and culverts, in conjunction with the stormwater sediment pond, comprise the IDFCS for the UEP. Drawing E1-114 depicts existing conditions at the UEP and identifies the interior perimeter channels and culverts and the stormwater sediment pond. The bottom elevation of the stormwater sediment pond is at approximately 26 feet and the top of stormwater sediment pond containment (coincident with the UEP embankment crest) is at approximate minimum elevation 41 feet. Discharge from the stormwater sediment pond is controlled by a principal spillway riser tower structure, which is a 6 foot by 6 foot square concrete box. The tower structure is fitted with six 16-inch diameter flanged pipe openings (with five being available for discharge) with the lowest available opening at invert elevation feet (Virginia Power, 1992). The principal spillway outfall pipe is a 24-inch diameter concrete pipe, which discharges to VPDES Permit Outfall 005. In this Plan, management of the inflow design flood is defined as having the capacity to convey the peak discharge resulting from the flood. The capacity of each stormwater runoff control feature was evaluated and compared to the peak discharge resulting from the inflow design flood (1,000-year flood). Hydrologic and hydraulic (H&H) analyses are contained in Appendix A. Information for the components of the IDFCS was obtained from the 2003 Closure Plan, New Ash Pond Stop Log Conversion, DCR (Virginia Power, 1992), site topographic mapping, and site observations. Constructed geometry for the interior perimeter channels and culverts is summarized in Table 1 and Table 2 respectively, along with the 1,000-year peak discharges and capacities. Table 1 Summary of Channel Geometry and Capacities Interior Perimeter Channel North Perimeter Channel Segment Number Lining Channel Slope (ft/ft) Bottom Width (ft) Depth* (ft) Side Slopes (Left, Right H:1V) 1,000- year peak discharge (cubic feet per second)** Capacity (cubic feet per second)** 1 Grass , Concrete , ,224 3 Concrete , ,562 West Perimeter Channel 1 Grass , South Perimeter Channel 1 Grass , Concrete , Concrete , ,984 4 Concrete , ,415 *For concrete channels, depth listed is the depth of concrete. Capacity listed includes grassed conveyance above the top of the concrete lining. ** Discharge and capacity are listed for the downstream end of a channel reach. C / October 2016

7 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia Page 5 Culvert Table 2 Summary of Culvert Properties and Capacities Material Diameter (ft) Length (ft) Culvert Slope (ft/ft) 1,000-year peak discharge (cubic feet per second) Capacity (cubic feet per second) East Culvert CMP * West Culvert Concrete Ductile Iron South Culvert CMP * * Capacity includes overflow channel to stormwater sediment pond. The analyses indicate that all interior perimeter channels and culverts that are part of the IDFCS are capable of passing the peak discharge from the 1,000-year flood. The UEP stormwater sediment pond was modeled for its performance during a 1,000-year flood. Appendix A contains calculations and results of the modeling. The model shows that the pool in the stormwater sediment pond from a 1,000-year flood would attain an estimated peak water surface elevation of feet. The UEP embankment crest provides containment from the stormwater sediment pond pool and has a minimum containment at approximate elevation 41 feet. Channels, culverts, and the stormwater sediment pond are routinely inspected (Dominion, 2014). These inspections meet the IDFCS requirements for maintenance in the CCR Rule. 3.4 Surface Water Requirements 40 CFR states that a facility shall not cause a discharge of pollutants into waters of the United States that is in violation of the National Pollutant Discharge Elimination System (NPDES) under section 402 of the Clean Water Act, as amended. DEQ administers the NPDES program in Virginia under the VPDES program. The UEP is regulated under an existing VPDES Permit. Discharges from the UEP are limited and monitored in accordance with the requirements in the VPDES permit, which functions to satisfy the requirements of (b) of the CCR Rule. 4.0 Conclusion It is GAI s opinion, based on a review of available material and additional analyses performed for this Plan, that the existing UEP Inflow Design Flood Control System is in compliance with the requirements in of the CCR Rule for a significant hazard impoundment. C / October 2016

8 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia Page References Dominion Report of 2014 Safety Inspection, Chesterfield Power Station Upper Ash Pond Dam. GAI Consultants Inc Dominion Chesterfield Power Station, Upper (East) Pond-Max Drawdown- Stability. GAI Consultants Inc Initial Hazard Potential Classification Assessment Report, Upper (East) Pond, Chesterfield Power Station, Chesterfield County, Virginia. United States Environmental Protection Agency CFR Parts 257 and 261 Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals from Electric Utilities; Final Rule. April 17, Virginia Department of Environmental Quality. Virginia Pollutant Discharge Elimination System (VPDES) Permit No. VA Virginia Power New Ash Pond Stop Log Conversion, DCR , January C / October 2016

9 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia DRAWING C / October 2016

10 PROJECT DRAWING TITLE PLAN VIEW - EXISTING CONDITIONS CLIENT DRAWN BY: CHECKED BY: APPROVED BY: NEIMAJC BORTZKM JOYCEJM GAI FILE NUMBER: C C-E1-114 DWG TYPE: SCALE: ISSUE DATE: ALT./CLIENT DRAWING NUMBER: UPPER (EAST) POND INFLOW DESIGN REPORT DOMINION AS SHOWN 10/7/2016 NO.: DATE: DWN: CHK: APV: DESCRIPTION: REVISION RECORD CHESTERFIELD POWER STATION CHESTERFIELD COUNTY, VIRGINIA GLEN ALLEN, VIRGINIA REVISION SHEET NO.: GAI DRAWING NUMBER: E1-114 ISSUING OFFICE: Murrysville 4200 Triangle Lane, Export, PA OF 1

11 Coal Combustion Residuals CCR Unit Inflow Design Flood Control System Plan Upper (East) Pond Chesterfield Power Station, Chesterfield County, Virginia APPENDIX A Hydrologic and Hydraulic Assessment C / October 2016

12 1 of 76 SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY BERKEME DATE 10/05/2016 PROJ. NO. C _ CHKD. BY URBANCE DATE 10/07/2016 APPENDIX A TABLE OF CONTENTS: SHEET* Objective. 2 Methodology. 2 References... 2 Rainfall Data.. 3 Curve Numbers 3 Time of Concentration Data 4 Summary of Hydraulic Calculations 4 Attachment 1 Drainage Area Map. 6 Attachment 2 Stage-Discharge for Pond.. 8 Attachment 3 Hydraflow Routing Attachment 2 Hydraulic Capacity for Channels. 37 Attachment 3 Hydraulic Capacity for Culverts. 62 *Appendix sheet numbers correspond to italic numbers in the upper right hand corner of each page. Z:\Energy\2015\C DOM-Chesterfld Pond Closu\Working Docs\CCR Rule documents\a initial submission and working folders\inflow Design Report\H&H Capacity Analysis-Significant - REV for CCR Compliance.docx

13 2 of 76 SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY BERKEME DATE 10/05/2016 PROJ. NO. C _ CHKD. BY URBANCE DATE 10/07/2016 OBJECTIVE: The purpose of this assessment is to estimate the hydrologic and hydraulic (H&H) capacity for the current site configuration at the Chesterfield Power Station s Upper (East) Pond (UEP) for the inflow design flood event to show compliance with the updated CCR Rule. Section of the Environmental Protection Agency (EPA) Coal Combustion Residual (CCR) Rule established in April 2015 states that the inflow design flood control system (for CCR surface impoundments) must adequately manage flow into the Impoundment during and following the peak discharge of the inflow design flood. The UEP (CCR) Impoundment is regulated as a significant hazard CCR surface impoundment, and per the CCR Rule, the inflow design flood is the 1,000-year event. This calculation will estimate peak discharges for the 1,000-year event for surface runoff control structures (channels, culverts, and stormwater sediment pond) that control and contain stormwater discharge from the impoundment. The peak discharges will be compared to calculated hydraulic capacity for each structure to demonstrate compliance with the CCR Rule. METHODOLOGY: Drainage areas to site features requiring evaluation were delineated using project mapping. A Drainage Area Map is included in these calculations (sheet 7). Under the inflow design flood, benches were assumed to be ineffective as diversions when delineating watersheds. The Natural Resources Conservation Service (NRCS) TR-55 method and the computer program Hydraflow Hydrographs were utilized to estimate peak flow rates to each runoff control structure. Hydraflow calculations are included as Attachment 2 to this calculation. Rainfall data for the site location were obtained from NOAA Atlas 14. REFERENCES 1. TR-55, Urban Hydrology For Small Watersheds, Natural Resources Conservation Services, June NOAA Atlas 14. Rainfall data for Dutch Gap Conservation Area, Accessed 12/10/2015 (for Closure Plan Calculations). 3. Hydraflow Hydrographs Extension for AutoCAD Civil 3D. Version 10 by Autodesk, Inc Tuck Mapping As-Built Contour Data. March 3, Upper (East) Pond Max Drawdown Stability Calculation, GAI Consultants Inc., December 17, Z:\Energy\2015\C DOM-Chesterfld Pond Closu\Working Docs\CCR Rule documents\a initial submission and working folders\inflow Design Report\H&H Capacity Analysis-Significant - REV for CCR Compliance.docx

14 3 of 76 SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY BERKEME DATE 10/05/2016 PROJ. NO. C _ CHKD. BY URBANCE DATE 10/07/ Revised Closure Plan, Upper (East) Pond, Chesterfield Power Station, Chesterfield County, Virginia. GAI Consultants, Inc Closure Plan Drawings, Upper East Pond, Chesterfield Power Station, Chesterfield County, Virginia. GAI Consultants, Inc Survey from D & M Surveyors P.C., September 29, RAINFALL DATA: Rainfall data for the site were obtained from Reference 2. These values are summarized below: 2-year, 24-hour event = 3.36 in (for use in Time of Concentration Calculation) 1,000-year, 24-hour event = 13.1 in CURVE NUMBERS: The following curve numbers used in the H&H Calculations of Reference 6 were also used for this assessment: The following curve numbers were used to represent the site conditions currently present: Coal Combustion Residuals (CCR) = 85 Vegetated Final Soil Cover (good condition) = 74 Gravel Haul Roads = 89 Z:\Energy\2015\C DOM-Chesterfld Pond Closu\Working Docs\CCR Rule documents\a initial submission and working folders\inflow Design Report\H&H Capacity Analysis-Significant - REV for CCR Compliance.docx

15 4 of 76 SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY BERKEME DATE 10/05/2016 PROJ. NO. C _ CHKD. BY URBANCE DATE 10/07/2016 Water (Stormwater Sediment Pond) = 98 The Hydraflow model was used to calculate a composite curve number for each watershed. TIME OF CONCENTRATION DATA: Time of concentration (TOC) flow paths were estimated within the Hydraflow model using the methods provided in TR-55, incorporating sheet flow, shallow concentrated flow, and channel flow segments. Slopes and channel dimensions were estimated from the project mapping which was developed from survey information (Reference 4). A minimum TOC of 6 minutes was used. The following roughness coefficients were used in the sheet flow calculations (Reference 6): CCR (No Vegetation) = 0.03 Final Cover with Good Vegetation = 0.24 Channel geometry and Manning s values for use in the TOC calculations were taken from Reference 6. SUMMARY OF HYDRAULIC CALCULATIONS: Capacity of the channels was estimated using the computer program Bentley FlowMaster (v8i), and capacity of the culverts was estimated using the Federal Highway Administration (FHWA) software HY-8. Channel dimensions and culvert properties were taken from References 4, 6, 7, and 8. Cross sections for each channel segment were taken at the downstream end of the channel segment where the entire watershed has contributed runoff. The stormwater sediment pond was modeled in Hydraflow, using the average end area method to estimate storage. Contour areas were estimated from Reference 4. The following Information on the pond s outlet structures was taken from References 5, 6, and 7 and entered into the Hydraflow model: Pond outfall culvert is 24-inches in diameter, with an inlet invert elevation of 12.0 and an outlet invert elevation of 7.6. The length of the culvert is approximately 192 (Reference 7). The riser tower has a crest elevation of 44.0 feet, and the inside of the riser is a 6 foot by 6 foot square (Reference 6). The riser has five open 16-inch diameter orifices with inverts at the following elevations feet, feet, feet, feet, and feet (Reference 5). The embankment is at elevation ft (Reference 7). Z:\Energy\2015\C DOM-Chesterfld Pond Closu\Working Docs\CCR Rule documents\a initial submission and working folders\inflow Design Report\H&H Capacity Analysis-Significant - REV for CCR Compliance.docx

16 5 of 76 SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY BERKEME DATE 10/05/2016 PROJ. NO. C _ CHKD. BY URBANCE DATE 10/07/2016 A summary of results is provided in Table 1 and Table 2. Table 1: Summary of Channel/Culvert Hydraulic Capacity Culvert/Channel 1,000-year peak flow rate (cfs) Capacity (cfs) North Perimeter Channel Segment North Perimeter Channel Segment ,224 North Perimeter Channel Segment ,562 South Perimeter Channel Segment South Perimeter Channel Segment South Perimeter Channel Segment ,984 South Perimeter Channel Segment ,415 West Perimeter Channel East Culvert (North Perimeter Channel) West Culvert (West Perimeter Channel) South Culvert (South Perimeter Channel) Table 2: Stormwater Sediment Basin Hydraulic Capacity Pond 1,000-year Water Surface Elevation (ft) Embankment Crest/Allowable WSE (ft) Stormwater Sediment Pond Z:\Energy\2015\C DOM-Chesterfld Pond Closu\Working Docs\CCR Rule documents\a initial submission and working folders\inflow Design Report\H&H Capacity Analysis-Significant - REV for CCR Compliance.docx

17 6 of 76 SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY BERKEME DATE 10/05/2016 PROJ. NO. C _ CHKD. BY URBANCE DATE 10/07/2016 ATTACHMENT 1 DRAINAGE AREA MAP Z:\Energy\2015\C DOM-Chesterfld Pond Closu\Working Docs\CCR Rule documents\a initial submission and working folders\inflow Design Report\H&H Capacity Analysis-Significant - REV for CCR Compliance.docx

18 7 of 76 DRAWING TITLE DRAWN BY: CHECKED BY: APPROVED BY: BERKEME URBANCE DWG TYPE: SCALE: ISSUE DATE: AS SHOWN --/--/---- EXISTING CONDITIONS - DRAINAGE AREA MAP PROJECT UPPER ASH POND IDFCSP CHESTERFIELD POWER STATION NO.: DATE: DWN: CHK: APV: DESCRIPTION: REVISION RECORD CHESTER CHESTERFIELD COUNTY, VIRGINIA ISSUING OFFICE: Murrysville 4200 Triangle Lane, Export, PA CLIENT DOMINION SHEET NO.: GLEN ALLEN, VIRGINIA GAI FILE NUMBER: MBB H&H Worksheet-REV ALT./CLIENT DRAWING NUMBER: GAI DRAWING NUMBER: REVISION E OF 1

19 8 of 76 SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY BERKEME DATE 10/05/2016 PROJ. NO. C _ CHKD. BY URBANCE DATE 10/07/2016 ATTACHMENT 2 STAGE-DISCHARGE FOR POND Z:\Energy\2015\C DOM-Chesterfld Pond Closu\Working Docs\CCR Rule documents\a initial submission and working folders\inflow Design Report\H&H Capacity Analysis-Significant - REV for CCR Compliance.docx

20 Chesterfield SEDIMENTATION POND STAGE-DISCHARGE ANALYSIS SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY URBANCE BERKEME DATE 06/15/2016 PROJ. NO. C _ CHKD. BY URBANCE BERKEME DATE 06/15/ of 76 Elev (ft) Head on first orifice row Flow in first row (cfs) Head on second orifice row Flow in second row (cfs) Head on third orifice row Flow in Head on third fourth row (cfs) orifice row Flow in fourth row (cfs) Head on fifth orifice row Flow in fifth row (cfs) Head on riser Orifice Flow in Weir Flow in Riser Riser Net Flow in Riser Head on Outlet Pipe Total Allowable Orifice Flow in Flow V^2 / 2g Outlet Pipe (cfs) Orifice Orifice Orifice Orifice Orifice RISER DATA BARREL HDPE - n = Circular - 16" Circular - 16" Circular - 16" Circular - 16" Circular - 16" Crest 44 Diameter (ft) 2 Invert Invert Invert Invert Invert Area (sf) Inlet Invert 12 Diam (in) Diam (in) Diam (in) Diam (in) Diam (in) Perimeter (ft) Outlet Invert 7.6 Area (sf) Area (sf) Area (sf) Area (sf) Area (sf) Weir C 3.33 Outlet TW centroid el centroid el centroid el centroid el centroid el Orifice C 0.6 Area (sf) C 0.6 C 0.6 C 0.6 C 0.6 C 0.6 Length (ft) 192 No. holes 1 No. holes 1 No. holes 1 No. holes 1 No. holes 1 Ke 0.5 R (ft) 0.5 The outlet pipe calculation is based on outlet control The equation used is the outlet control equation in HDS - 5: H = (1 + Ke + (29 * n^2 * L)/R^1.33) * V^2 / 2g Chesterfield sed pond discharge.xlsx Riser Discharge north

21 10 of 76 SUBJECT CHESTERFIELD POWER STATION-UPPER (EAST) POND _ HYDROLOGIC AND HYDRAULIC CAPACITY ASSESSMENT _ BY BERKEME DATE 10/05/2016 PROJ. NO. C _ CHKD. BY URBANCE DATE 10/07/2016 ATTACHMENT 3 HYDRAFLOW ROUTING Z:\Energy\2015\C DOM-Chesterfld Pond Closu\Working Docs\CCR Rule documents\a initial submission and working folders\inflow Design Report\H&H Capacity Analysis-Significant - REV for CCR Compliance.docx

22 1 11 of 76 Watershed Model Schematic Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v Project: Chesterfield Hydraulic Capacity REV-1000yr.gpw Tuesday, 06 / 14 / 2016

23 Hydrograph Summary Report 2 12 of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph No. type flow interval Peak volume hyd(s) elevation strge used Description (origin) (cfs) (min) (min) (cuft) (ft) (cuft) 1 SCS Runoff , South Perimeter Channel 1 2 SCS Runoff , South Perimeter Channel 2 3 Combine ,907 1, SPC 2 Total 4 SCS Runoff ,233, South Perimeter Channel 3 5 Combine ,573,200 3, Total flow to South Perimeter Channe 6 SCS Runoff , South Perimeter Channel 4 7 Combine ,239,426 5, South Perimeter Total 8 SCS Runoff , West Perimeter Channel (West Culve 9 SCS Runoff , North Perimeter Channel 1 10 Combine ,436 8, NPC 1 Total 11 SCS Runoff , North Perimeter Channel 2 12 Combine ,334 10, NPC 2 Total 13 SCS Runoff , North Perimeter Channel 3 14 Combine ,130,716 12, North Perimeter Channel Total 15 SCS Runoff , Temporary Sed Pond 16 Combine ,257,634 7, 14, Total To Sed Pond 17 Reservoir ,653, ,247,439 <no description> Note: Hydraflow does not have an input option for a 1,000yr return interval, so the 1,000yr rainfall was entered as input for the 10yr return period. Chesterfield Hydraulic Capacity REV-1000yr.gpw Return Period: 10 Year Tuesday, 06 / 14 / 2016

24 Hydrograph Report 3 13 of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 1 South Perimeter Channel 1 Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 717 min Time interval = 1 min Hyd. volume = 155,489 cuft Drainage area = ac Curve number = 74* Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 6.00 min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 * Composite (Area/CN) = [(3.600 x 85) + (7.300 x 74)] / Q (cfs) South Perimeter Channel 1 Hyd. No Year Q (cfs) Hyd No. 1 Time (min)

25 Hydrograph Report 4 14 of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 2 South Perimeter Channel 2 Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 717 min Time interval = 1 min Hyd. volume = 184,418 cuft Drainage area = ac Curve number = 74 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 6.00 min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Q (cfs) South Perimeter Channel 2 Hyd. No Year Q (cfs) Hyd No. 2 Time (min)

26 Hydrograph Report 5 15 of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 3 SPC 2 Total Hydrograph type = Combine Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 717 min Time interval = 1 min Hyd. volume = 339,907 cuft Inflow hyds. = 1, 2 Contrib. drain. area = ac Q (cfs) SPC 2 Total Hyd. No Year Q (cfs) Time (min) Hyd No. 3 Hyd No. 1 Hyd No. 2

27 Hydrograph Report 6 16 of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 4 South Perimeter Channel 3 Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 734 min Time interval = 1 min Hyd. volume = 1,233,292 cuft Drainage area = ac Curve number = 78* Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = TR55 Time of conc. (Tc) = min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 * Composite (Area/CN) = [( x 85) + ( x 74)] / Q (cfs) South Perimeter Channel 3 Hyd. No Year Q (cfs) Time (min) Hyd No. 4

28 TR55 Tc Worksheet 7 17 of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Hyd. No. 4 South Perimeter Channel 3 Description A B C Totals Sheet Flow Manning's n-value = Flow length (ft) = Two-year 24-hr precip. (in) = Land slope (%) = Travel Time (min) = = Shallow Concentrated Flow Flow length (ft) = Watercourse slope (%) = Surface description = Unpaved Unpaved Unpaved Average velocity (ft/s) = Travel Time (min) = = Channel Flow X sectional flow area (sqft) = Wetted perimeter (ft) = Channel slope (%) = Manning's n-value = Velocity (ft/s) = Flow length (ft) ({0}) Travel Time (min) = = 1.56 Total Travel Time, Tc min

29 Hydrograph Report 8 18 of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 5 Total flow to South Perimeter Channel 3 Hydrograph type = Combine Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 719 min Time interval = 1 min Hyd. volume = 1,573,200 cuft Inflow hyds. = 3, 4 Contrib. drain. area = ac Q (cfs) Total flow to South Perimeter Channel 3 Hyd. No Year Q (cfs) Time (min) Hyd No. 5 Hyd No. 3 Hyd No. 4

30 Hydrograph Report 9 19 of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 6 South Perimeter Channel 4 Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 737 min Time interval = 1 min Hyd. volume = 666,227 cuft Drainage area = ac Curve number = 74 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = TR55 Time of conc. (Tc) = min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Q (cfs) South Perimeter Channel 4 Hyd. No Year Q (cfs) Time (min) Hyd No. 6

31 TR55 Tc Worksheet of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Hyd. No. 6 South Perimeter Channel 4 Description A B C Totals Sheet Flow Manning's n-value = Flow length (ft) = Two-year 24-hr precip. (in) = Land slope (%) = Travel Time (min) = = Shallow Concentrated Flow Flow length (ft) = Watercourse slope (%) = Surface description = Unpaved Unpaved Paved Average velocity (ft/s) = Travel Time (min) = = Channel Flow X sectional flow area (sqft) = Wetted perimeter (ft) = Channel slope (%) = Manning's n-value = Velocity (ft/s) = Flow length (ft) ({0}) Travel Time (min) = = 2.01 Total Travel Time, Tc min

32 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 7 South Perimeter Total Hydrograph type = Combine Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 734 min Time interval = 1 min Hyd. volume = 2,239,426 cuft Inflow hyds. = 5, 6 Contrib. drain. area = ac Q (cfs) South Perimeter Total Hyd. No Year Q (cfs) Time (min) Hyd No. 7 Hyd No. 5 Hyd No. 6

33 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 8 West Perimeter Channel (West Culvert) Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 717 min Time interval = 1 min Hyd. volume = 54,240 cuft Drainage area = ac Curve number = 74 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 6.00 min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Q (cfs) West Perimeter Channel (West Culvert) Hyd. No Year Q (cfs) Hyd No. 8 Time (min)

34 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 9 North Perimeter Channel 1 Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 721 min Time interval = 1 min Hyd. volume = 403,196 cuft Drainage area = ac Curve number = 84* Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = TR55 Time of conc. (Tc) = min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 * Composite (Area/CN) = [(4.300 x 85) + (0.630 x 89) + (5.270 x 74)] / Q (cfs) North Perimeter Channel 1 Hyd. No Year Q (cfs) Time (min) Hyd No. 9

35 TR55 Tc Worksheet of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Hyd. No. 9 North Perimeter Channel 1 Description A B C Totals Sheet Flow Manning's n-value = Flow length (ft) = Two-year 24-hr precip. (in) = Land slope (%) = Travel Time (min) = = 2.64 Shallow Concentrated Flow Flow length (ft) = Watercourse slope (%) = Surface description = Unpaved Unpaved Paved Average velocity (ft/s) = Travel Time (min) = = 3.93 Channel Flow X sectional flow area (sqft) = Wetted perimeter (ft) = Channel slope (%) = Manning's n-value = Velocity (ft/s) = Flow length (ft) ({0}) Travel Time (min) = = 5.85 Total Travel Time, Tc min

36 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 10 NPC 1 Total Hydrograph type = Combine Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 720 min Time interval = 1 min Hyd. volume = 457,436 cuft Inflow hyds. = 8, 9 Contrib. drain. area = ac Q (cfs) NPC 1 Total Hyd. No Year Q (cfs) Time (min) Hyd No. 10 Hyd No. 8 Hyd No. 9

37 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 11 North Perimeter Channel 2 Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 730 min Time interval = 1 min Hyd. volume = 288,896 cuft Drainage area = ac Curve number = 74 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = TR55 Time of conc. (Tc) = min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Q (cfs) North Perimeter Channel 2 Hyd. No Year Q (cfs) Time (min) Hyd No. 11

38 TR55 Tc Worksheet of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Hyd. No. 11 North Perimeter Channel 2 Description A B C Totals Sheet Flow Manning's n-value = Flow length (ft) = Two-year 24-hr precip. (in) = Land slope (%) = Travel Time (min) = = Shallow Concentrated Flow Flow length (ft) = Watercourse slope (%) = Surface description = Unpaved Unpaved Unpaved Average velocity (ft/s) = Travel Time (min) = = Channel Flow X sectional flow area (sqft) = Wetted perimeter (ft) = Channel slope (%) = Manning's n-value = Velocity (ft/s) = Flow length (ft) ({0}) Travel Time (min) = = 2.31 Total Travel Time, Tc min

39 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 12 NPC 2 Total Hydrograph type = Combine Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 721 min Time interval = 1 min Hyd. volume = 746,334 cuft Inflow hyds. = 10, 11 Contrib. drain. area = ac Q (cfs) NPC 2 Total Hyd. No Year Q (cfs) Time (min) Hyd No. 12 Hyd No. 10 Hyd No. 11

40 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 13 North Perimeter Channel 3 Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 731 min Time interval = 1 min Hyd. volume = 384,385 cuft Drainage area = ac Curve number = 75* Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = TR55 Time of conc. (Tc) = min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 * Composite (Area/CN) = [(0.700 x 89) + ( x 74)] / Q (cfs) North Perimeter Channel 3 Hyd. No Year Q (cfs) Time (min) Hyd No. 13

41 TR55 Tc Worksheet of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Hyd. No. 13 North Perimeter Channel 3 Description A B C Totals Sheet Flow Manning's n-value = Flow length (ft) = Two-year 24-hr precip. (in) = Land slope (%) = Travel Time (min) = = Shallow Concentrated Flow Flow length (ft) = Watercourse slope (%) = Surface description = Unpaved Unpaved Paved Average velocity (ft/s) = Travel Time (min) = = Channel Flow X sectional flow area (sqft) = Wetted perimeter (ft) = Channel slope (%) = Manning's n-value = Velocity (ft/s) = Flow length (ft) ({0}) Travel Time (min) = = 3.80 Total Travel Time, Tc min

42 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 14 North Perimeter Channel Total Hydrograph type = Combine Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 722 min Time interval = 1 min Hyd. volume = 1,130,716 cuft Inflow hyds. = 12, 13 Contrib. drain. area = ac Q (cfs) North Perimeter Channel Total Hyd. No Year Q (cfs) Time (min) Hyd No. 14 Hyd No. 12 Hyd No. 13

43 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 15 Temporary Sed Pond Hydrograph type = SCS Runoff Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 726 min Time interval = 1 min Hyd. volume = 887,493 cuft Drainage area = ac Curve number = 84* Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = TR55 Time of conc. (Tc) = min Total precip. = in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 * Composite (Area/CN) = [(6.800 x 100) + ( x 74)] / Q (cfs) Temporary Sed Pond Hyd. No Year Q (cfs) Time (min) Hyd No. 15

44 TR55 Tc Worksheet of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Hyd. No. 15 Temporary Sed Pond Description A B C Totals Sheet Flow Manning's n-value = Flow length (ft) = Two-year 24-hr precip. (in) = Land slope (%) = Travel Time (min) = = Shallow Concentrated Flow Flow length (ft) = Watercourse slope (%) = Surface description = Unpaved Unpaved Unpaved Average velocity (ft/s) = Travel Time (min) = = 3.75 Channel Flow X sectional flow area (sqft) = Wetted perimeter (ft) = Channel slope (%) = Manning's n-value = Velocity (ft/s) = Flow length (ft) ({0}) Travel Time (min) = = 0.00 Total Travel Time, Tc min

45 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 16 Total To Sed Pond Hydrograph type = Combine Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 723 min Time interval = 1 min Hyd. volume = 4,257,634 cuft Inflow hyds. = 7, 14, 15 Contrib. drain. area = ac Q (cfs) Total To Sed Pond Hyd. No Year Q (cfs) Time (min) Hyd No. 16 Hyd No. 7 Hyd No. 14 Hyd No. 15

46 Hydrograph Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Hyd. No. 17 <no description> Hydrograph type = Reservoir Peak discharge = cfs Storm frequency = 10 yrs Time to peak = 859 min Time interval = 1 min Hyd. volume = 3,653,877 cuft Inflow hyd. No. = 16 - Total To Sed Pond Max. Elevation = ft Reservoir name = SW Sed Pond (with Rating Curve) Max. Storage = 3,247,439 cuft Storage Indication method used. Wet pond routing start elevation = ft. Q (cfs) <no description> Hyd. No Year Q (cfs) Time (min) Hyd No. 17 Hyd No. 16 Total storage used = 3,247,439 cuft

47 Pond Report of 76 Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2013 by Autodesk, Inc. v10 Tuesday, 06 / 14 / 2016 Pond No. 6 - SW Sed Pond (with Rating Curve) Pond Data Contours -User-defined contour areas. Average end area method used for volume calculation. Begining Elevation = ft Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft) , , , , , , , , ,612 1,057, , ,747 1,284, , ,272 1,517, , ,108 1,757, , ,538 2,005, , ,109 2,259, , ,264 2,519, , ,880 2,786, , ,566 3,063, , ,264 3,378, , ,030 3,867, , ,318 4,501, , ,318 5,135, , ,318 5,770,160 Culvert / Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise (in) = Span (in) = No. Barrels = Invert El. (ft) = Length (ft) = Slope (%) = n/a N-Value = n/a Orifice Coeff. = Multi-Stage = n/a No No No Crest Len (ft) = Crest El. (ft) = Weir Coeff. = Weir Type = Multi-Stage = No No No No Exfil.(in/hr) = (by Wet area) TW Elev. (ft) = 0.00 Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s). Stage / Storage / Discharge Table Stage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Total ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs , , ,057, ,284, ,517, ,757, ,005, ,259, ,519, ,786, ,063, ,378, ,867, ,501, ,135, ,770,