McElroy s Run Impoundment Inflow Design Flood Control System Plan

Transcription

1 McElroy s Run Impoundment Inflow Design Flood Control System Plan Allegheny Energy Supply Company, LLC A FirstEnergy Company Pleasants Power Station Pleasants County, West Virginia October 2016 Prepared for: Allegheny Energy Supply Company, LLC A FirstEnergy Company 800 Cabin Hill Drive Greensburg, Pennsylvania Prepared by: GAI Consultants, Inc. Murrysville Office 4200 Triangle Lane Export, Pennsylvania

2 McElroy s Run Impoundment Inflow Design Flood Control System Plan Allegheny Energy Supply Company, LLC, A FirstEnergy Company Pleasants Power Station, Pleasants County, West Virginia Page i Table of Contents Certification/Statement of Professional Opinion... ii 1.0 Introduction Plan Overview Initial Inflow Design Flood Control System Plan Impoundment Design Embankment Design Principal Spillway Design Emergency Spillway Hydrologic and Hydraulic Capacity Requirements Probable Maximum Flood Routing Conclusion References... 6 Figure Appendix A Hydrologic and Hydraulic Analysis/Capacity Estimate 2016 GAI Consultants C , Task 006 / October 2016

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4 McElroy s Run Impoundment Inflow Design Flood Control System Plan Allegheny Energy Supply Company, LLC, A FirstEnergy Company Pleasants Power Station, Pleasants County, West Virginia Page Introduction The Pleasants Power Station (Station) is a coal-fired electric generating station located near the community of Willow Island in Pleasants County, WV. The Station consists of two generating units, which are capable of producing 1,300 megawatts of electricity. CCRs generated at the Station are placed in the McElroy s Run CCR Surface Impoundment, which is located approximately one-half mile east-southeast of the Station. The McElroy s Run CCR Surface Impoundment (Impoundment) is a captive facility located at the Pleasants and Willow Island Power Station located in Willow Island, Pleasants County, WV. The Impoundment receives flue gas desulfurization scrubber by-product generated at the Station, effluent from the recirculation system through Sedimentation Ponds 1 and 2 of the adjacent landfill and their underdrains, and waste materials collected primarily as a result of general house-cleaning maintenance and/or repair at the Pleasants Power Station. According to the WV Title 47 Legislative Rule, Series 34 Dam Safety Rule, the Impoundment has a Hazard Classification of Class I, meaning the failure of the Impoundment may cause loss of human life or major damage to dwellings, buildings, railroads, or important utilities. The initial Hazard Assessment classifies McElroy s Impoundment as a High-Hazard Dam. The dam of the Impoundment is approximately 243 feet (ft.) high with a maximum storage of approximately 20,000 acre-ft. The crest of the dam is at elevation (El.) 900 ft., with El ft. as the permitted final level of CCR and recommended normal operating pool level. The Impoundment area is approximately 253 acres. 2.0 Plan Overview 40 CFR requires CCR surface impoundments have inflow design flood control system (IDFCS), and (a)(3) outlines the design flood for CCR surface impoundments. The Impoundment is a high hazard potential CCR surface impoundment, and as such, the inflow design flood shall be the probable maximum flood (PMF). This Plan has been prepared to demonstrate that the IDFCS at the Impoundment adequately manages flow during the PMF. Flood controls at the Impoundment include the following: a principal spillway consisting of a concrete discharge tower and outfall barrel; a siphon float; and a concrete emergency spillway. 3.0 Initial Inflow Design Flood Control System Plan This Plan provides a description of the Impoundments design, including a description of its features such as: embankment; principal spillway (does not normally flow); siphon float (primary discharge); and emergency spillway. The Hydrologic and Hydraulic (H&H) Capacity for the Impoundment is also described. C , Task 006 / October 2016

5 McElroy s Run Impoundment Inflow Design Flood Control System Plan Allegheny Energy Supply Company, LLC, A FirstEnergy Company Pleasants Power Station, Pleasants County, West Virginia Page Impoundment Design The Impoundment utilizes an embankment to impound and store station process water and wet CCR slurries. There are three structures that could potentially discharge from the impoundment: the principal spillway riser, siphon line, and the emergency spillway Embankment Design The Impoundment s embankment is maintained as a solid waste surface impoundment/dam operated under a NPDES Water Pollution Control Permit (WV ). The dam is 1900 feet long and 243 feet high with a maximum storage of approximately 20,000 acre-feet and an approximate CCR surface area of 253 acres. The dam crest is located at El. 900 feet and is 70 feet in width, allowing for a final permitted CCR level at El The top of the dam is part grass and part access road. An annual Embankment Inspection conducted in December 2015 demonstrated that the embankment is in a structurally sound condition (Reference 2) based on an annual Embankment Inspection conducted in December The drainage area to the dam embankment is approximately 349 acres, and the reservoir has a surface area of approximately 282 acres at the top of the dam crest Principal Spillway Design The principal spillway riser structure has a two-foot by two-foot opening at El. 890 feet. The spillway maintains an operational sluice gate at El. 885 feet, which is kept closed due to the operating Water Surface Elevation being above El The principal spillway outfall pipe is a 36-inch concrete pipe culvert that is 3,600 feet long and flows underneath the dam. The outfall pipe discharges to a concrete channel that leads to McElroy s Run Creek. The principal Spillway typically does not flow under normal operation of the dam. The normal operating surface of the Impoundment is approximately El. 887 feet, which is three feet below the uppermost opening in the principal spillway riser structure. Discharge from the riser structure does not occur for storm events less than or equal to the 25-year, 24- hour storm, as per the NPDES Discharge Permit. The structure is in structurally sound condition as of an Annual Embankment Inspection conducted in December, 2014 (Reference 5). The Impoundment utilizes a siphon line as the current method of primary discharge and to maintain the normal operating pool level of El. 887 ft. The siphon is 12 inches in diameter and can convey water to the Station for reuse or discharge to the Ohio River via a permitted outfall. The discharge of the siphon is typically 3,000 GPM, but varies depending upon Impoundment operations Emergency Spillway The Impoundment also has an emergency spillway. When looking downstream, the spillway is located on the left (west) abutment of the dam and is 20 feet in width with a crest elevation of feet. The spillway is concrete lined and has an approach lined with stone rip-rap. The spillway outlet is protected with grouted rip-rap. The Annual Embankment Inspection conducted in June 2015 found that the concrete lined spillway channel is in good condition with no significant deterioration of the concrete. 3.2 Hydrologic and Hydraulic Capacity Requirements The Impoundment must operate an IDFCS to manage the PMF. When the Impoundment was originally permitted in 1978, it was designed to pass 80 percent of the Probable Maximum Precipitation (PMP) with three feet of freeboard. In 1992, the WV Regulations were revised to require the dam to safely C , Task 006 / October 2016

6 McElroy s Run Impoundment Inflow Design Flood Control System Plan Allegheny Energy Supply Company, LLC, A FirstEnergy Company Pleasants Power Station, Pleasants County, West Virginia Page 5 pass or store 100 percent of the PMP. The freeboard requirement was removed and existing dams were not required to become re-certified for the PMP (Reference 3). A Reservoir Management Plan was prepared in 2003 that included an analysis to establish the operating level in the reservoir. The operating level was established so that at least one-foot of freeboard would be provided below the emergency spillway during the six-hour, 0.8 PMP. The design criteria of 0.8 PMP was established in 1978 under the original dam permit (Reference 4). The Federal CCR Rule states that high hazard surface impoundments must be designed to effectively manage the PMF storm event. Therefore, the current West Virginia Dam Safety regulations were referenced to determine the PMP storm duration that generates the PMF. The West Virginia regulations state that high hazard dams must be designed to effectively manage the Probable Maximum Flood resulting from a six-hour PMP storm. (West Virginia Title 47 47CSR34 paragraph a.A, Reference 3). As such, the 6-hour PMP storm was modeled to determine if the impoundment is in compliance with the Federal CCR Rule Probable Maximum Flood Routing The PMP storm duration, determined by the WV Dam Safety Regulations, is used to determine the PMF event required to satisfy the Federal CCR Rule. The PMF was routed through the dam using the software programs HEC-HMS (Version 4.1.0) and Hydraflow Hydrographs (Version ) to identify if the reservoir s storage capabilities are in compliance with the WV Dam Safety Regulations and the Federal CCR Rule. (Reference 1 and 3). Refer to Appendix A for the H&H Analysis/Capacity Estimate which includes routing calculations for the PMF. As described in the H&H Analysis/Capacity Estimate (Appendix A), the Impoundment has a peak water surface El. of feet under PMF conditions. The flow depth in the emergency spillway is 1.3 feet in the control section, and the flow through the emergency spillway was estimated to be approximately 100 cubic feet per second (cfs). The hydraulic capacity of the emergency spillway is estimated to be approximately 9,000 cfs, so the PMF flow is well below the spillway s capacity. The shear stress in the spillway during the maximum discharge is estimated to be approximately 0.66 pounds per square foot, which is not expected to cause instability of the concrete. The hydraulic capacity estimate demonstrates that Impoundment has adequate storage and outlet structures to pass the PMF event. Thus, the Impoundment is in compliance with the CCR Rule. 4.0 Conclusion A hydrologic and hydraulic assessment was conducted to estimate the water surface elevation in the PMF event. It was found that McElroy s Run Dam has adequate storage and outlet structures to pass the PMF event determined by the WV Dam Safety Regulations (Reference 3). The assessment demonstrates that the dam is in compliance with the 2015 CCR Rule. C , Task 006 / October 2016

7 McElroy s Run Impoundment Inflow Design Flood Control System Plan Allegheny Energy Supply Company, LLC, A FirstEnergy Company Pleasants Power Station, Pleasants County, West Virginia Page References 1. United States Environmental Protection Agency 40 CFR Parts 257 and 261 Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals from Electric Utilities; Final Rule. April 17, GAI Consultant s Inc., McElroy s Run Impoundment Coal Combustion Residual Annual Report, Pleasants Power Station, Pleasants County, West Virginia. December, West Virginia Secretary of State Chapter 22 Article 14 Dam Control and Safety Act. 4. GAI Consultants Inc., Reservoir Management Plan and Hydraulic Design Report, McElroy s Run CCB Impoundment, Pleasants Power Station, Pleasants County, West Virginia January GAI Consultants Inc., Results from Structural Condition Assessment of Primary Pipe and Decant Tower, Pleasants Power Station, Willow Island, West Virginia. C , Task 006 / October 2016

8 McElroy s Run Impoundment Inflow Design Flood Control System Plan Allegheny Energy Supply Company, LLC, A FirstEnergy Company Pleasants Power Station, Pleasants County, West Virginia FIGURE C , Task 006 / October 2016

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10 McElroy s Run Impoundment Inflow Design Flood Control System Plan Allegheny Energy Supply Company, LLC, A FirstEnergy Company Pleasants Power Station, Pleasants County, West Virginia APPENDIX A Hydrologic and Hydraulic Analysis/Capacity Estimate C , Task 006 / October 2016

11 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 1 of 12 REV. BY: ODONNDM DATE: 4/12/2016 REV CHK BY: BERKEME DATE: 4/18/2016 PURPOSE The purpose of this analysis is to estimate the capacity of the existing impoundment for the full PMP 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 mange flow into the Impoundment during and following the peak discharge of the inflow design flood. The McElroy s Run (CCR) Impoundment is regulated as a high hazard CCR surface impoundment, and per the CCR Rule, the inflow design flood is the Probable Maximum Flood (PMF) which is based on the Probable Maximum Precipitation (PMP). The CCR Impoundment s Reservoir Management Plan prepared by GAI in 2003 states that the Impoundment operation is to be such that to maintain at least 1 foot of freeboard between the crest of the emergency spillway (elevation ft) and the maximum water level in the reservoir for a 6 hour, 80% PMP (6 hour, 0.8 PMP). The analysis will include an assessment of stage/storage in the reservoir based on existing topographic mapping (provided by First Energy in 2015), development of PMP rainfall distribution, verification of the reservoir drainage area, and routing of the PMF event. REFERENCES 1. CHA, Assessment of Dam Safety-Coal Combustion Surface Impoundments (Task 3) Final Report. CHA, April 21, Environmental Protection Agency (EPA), Federal Register. Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals from Electric Utilities. 40 CFR Parts 257 and 261. Volume 80, Number 74. April 17, First Energy, Existing Topography Mapping Mapping Generated April 11, 2015 and supplemented with topography (below elevation 886.7) from a fathometer survey performed by GAI on June 1-5, GAI Consultants, Inc., Results from Structural Condition Assessment of Primary Principal Spillway Pipe and Decant Tower-Pleasants Power Station GAI, February 12, GAI Consultants, Inc., Reservoir Management Plan and Hydraulic Design Report, McElroy s Run CCB Impoundment, Pleasants Power Station, Pleasants County, West Virginia January National Weather Service, Hydrometeorological Report No. 51 Probable Maximum Precipitation Estimates, United States East of the 105 th Meridian. June Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

12 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 2 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 DESIGN CRITERIA Per the CCR Rule (Reference 2) the inflow design flood is the PMF, and the West Virginia Dam Safety Regulations state that high-hazard dams West Virginia Title (47 47CSR34 paragraph 7.1.a.2.A) must be designed to effectively manage the Probable Maximum Precipitation for a six hour storm. DETERMINATION OF PMP Reference 6 was used to determine the PMP for the site. Calculations are included as Attachment 1. STAGE STORAGE ESTIMATE The stage storage curve of the reservoir was estimated using current topographic mapping (Reference 3). The current topography indicates less storage than the amounts listed in the Reservoir Management Plan (Reference 5). The hydraulic models have been prepared for the estimated stage/storage developed from current topology. A Stage Storage curve based on the 2015 aerial mapping is presented below. 900 Stage Storage 895 Emergency Spillway Elev CCR Level Elevation (ft) ,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 Storage (ac-ft) Figure 1: Stage-Storage Curve (Based on 2015 Aerial Mapping) Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

13 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 3 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 HYDROLOGY CALCULATIONS The hydraulic model requires inputs for a drainage area, runoff curve number, and lag time (60 % of the time of concentration) for each watershed. TR-55 methodology was used to determine the Curve Number and Lag Time of the watershed. The watershed is mostly forested, with a mix of type B and type C soils, as determined by NRCS Web Soil Survey (Attachment 2). Table 1 summarizes these parameters for the reservoir and upslope watershed to McElroy s Impoundment. The Drainage Area Map, Runoff Curve Number, and Time of Concentration Calculations are included as Attachment 2. Table 1: Summary of Hydrologic Parameters Drainage Area Runoff Curve Number Lag Time (min) Reservoir 282 ac (0.44 sq mi) Upslope Watershed 349 ac (0.55 sq mi) ROUTING The computer programs HEC-HMS (Version 4.1.0) and Hydraflow Hydrographs (Version ) were used to route the PMP event. The following conditions apply to the hydraulic modeling (from Reference 4): 1. The principal spillway (riser) begins at a 2x2 foot opening in the riser at elevation 890 feet; 2. The principal spillway outfall pipe is a 36-inch diameter concrete pipe culvert 3,600 feet long with an inlet invert elevation at ft and an outlet invert elevation of ft; 3. The spillway gate at 885 ft is closed, and it was assumed to be non-operational for this analysis; 4. The normal operating water surface elevation in the reservoir is supposed to be approximately 887 ft, however for this assessment routing was started at the principal spillway opening (el. 890 ft); 5. The siphon used to control water surface elevation in the reservoir is assumed to be nonoperational during the PMF event; 6. The emergency spillway is approximately 20 feet wide with a crest elevation of ft and 3:1 side slopes; 7. The top of the dam embankment was assumed to be at elevation ft; Rating curves for the outlet structures were developed using Hydraflow Hydrographs. These rating curves were input into HEC-HMS, which was used to model a 6 hour, PMP rainfall. The water surface elevation in the reservoir during the PMF event was estimated to be ft from HEC-HMS. Thus, 5.2 feet of freeboard will be provided between the reservoir elevation and the top of the embankment during the PMF. The Hydraflow Input, Outflow Table, Rating Curve and HEC-HMS input and output are presented below and on the following pages. Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

14 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 4 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 Pond Report Hydraflow Hydrographs by Intelisolve Pond No. 1 - McElroy's Impoundment Pond Data Pond storage is based on known contour areas. Average end area method used. Tuesday, Apr , 9:49 AM Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft) , , , , , ,649 1,316, ,094,978 1,761,173 3,077, ,465,878 2,560,856 5,638, ,849,255 3,315,133 8,953, ,419,602 4,268,857 13,222, ,910,181 5,329,782 18,552, ,508,075 6,418,256 24,970, ,562,157 8,070,232 33,041, ,777,100 11,339,260 44,380, ,558,028 16,335,130 60,715, ,700,120 20,258,150 80,973, ,228,810 21,928, ,902, ,568,040 22,796, ,699, ,839,900 23,407, ,107, ,112,130 23,952, ,059, ,396,210 24,508, ,567,700 Culvert / Orifice Structures Weir Structures [A] [B] [C] [D] [A] [B] [C] [D] Rise (in) = Span (in) = No. Barrels = Invert El. (ft) = Length (ft) = Slope (%) = N-Value = Orif. Coeff. = Multi-Stage = n/a Yes No No Crest Len (ft) = Crest El. (ft) = Weir Coeff. = Weir Type = Riser Broad Multi-Stage = Yes No No No Exfiltration = in/hr (Contour) Tailwater Elev. = 0.00 ft Stage / Storage / Discharge Table Note: Culvert/Orifice outflows have been analyzed under inlet and outlet control. Weir riser checked for orifice conditions. Stage Storage Elevation Clv A Clv B Clv C Clv D Wr A Wr B Wr C Wr D Exfil Total ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs , ,316, ,077, ,638, ,953, ,222, ,552, ,970, ,041, ,380, ,715, ,973, ,902, ,699, ,107, ,059, ,567, Figure 2: Pond Report from Hydraflow Hydrogaphs Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

15 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 5 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 Figure 3: Discharge Rating Curve (used to estimate flow through Emergency Spillway during PMF event). Figure 4: Basin Model (HEC-HMS) Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

16 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 6 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 Figure 5: Hydrologic Input Data (HEC-HMS) Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

17 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 7 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 Figure 6: PMP Distribution Input (HEC-HMS) Figure 7: Elevation-Area Input (HEC-HMS) Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

18 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 8 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 Figure 8: Elevation-Discharge Input (HEC-HMS) Figure 9: Global Summary (HEC-HMS) Figure 10: McElroy s Dam Summary (HEC-HMS) Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

19 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 9 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 EMERGENCY SPILLWAY CAPACITY ESTIMATE The emergency spillway crest is located at elevation ft, so the flow depth in the spillway will be 1.3 ft in the control section, and per the rating curve developed using Hydraflow Hydrographs (Figure 3), flow through the spillway is estimated to be approximately 100 cfs. Manning s equation and the software Bentley FlowMaster was used to estimate flow depth, stability, and capacity of the sloped portion of the emergency spillway under the PMF flow. Figure 11: Estimation of Flow Depth in Emergency Spillway Channel during PMF Event (Bentley FlowMaster) Using the formula for shear stress, T = 62.4 d x s, where d is flow depth and s is slope, the shear stress in the spillway is approximately 0.66 psf. Thus the shear stress and velocity are below the allowable limits for concrete. The spillway is approximately 6.5 feet deep, making its capacity approximately 9,000 cfs (as shown below). Thus, the PMF flow through the spillway of 100 cfs is well below the spillway s capacity. Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

20 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 10 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 Figure 12: Estimation of Emergency Spillway Capacity (Bentley FlowMaster) CONCLUSION A hydrologic and hydraulic assessment was conducted to estimate the water surface elevation in the reservoir during the PMF event. It was found that McElroy s dam has adequate storage and outlet structures to pass the PMF event. Thus, this analysis demonstrates that the dam is in compliance with the 2015 amendments to the CCR Rule. Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

21 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 11 of 12 REV. BY ODONNDM DATE 4/12/2016 REV CHK BY: BERKEME DATE 4/18/2016 Attachment 1 PMP Distribution Calculation Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

22 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT PMP PRECIPITATION DISTRIBUTIONS BY ODONNDM DATE 12/21/2015 PROJ. NO. C CHKD. BY BERKEME DATE 12/21//2015 SHEET NO. 1 OF 4 INTRODUCTION The McElroy s Run CCR Impoundment is regulated as a high hazard dam. The Environmental Protection Agency Coal Combustion Residual (CCR) rule established in April 2015, section states that inflow design flood control systems for high hazard potential surface impoundments must adequately manage inflow resulting from the Probable Maximum Flood (PMF). Using National Oceanic and Atmospheric Administration/National Weather Service documents, this calculation will determine the Probable Maximum Precipitation (PMP) at the site for a variety of storm durations. The PMP will be used to determine the PMF. PRECIPITATION The National Weather Service s Hydrometeorological Report No. 51 (HMR-51), Probable Maximum Precipitation Estimates, United States East of the 105 th Meridian contains charts that show the PMP for watersheds of various sizes and for various durations. The charts for the PMP for a 10-square mile watershed are attached on the next 3 pages, and they show the PMP for a 6-hour, 12-hour, 24- hour, 48-hour, and 72-hour storm. The drainage area for McElroy s Run CCR Impoundment is 0.98 square miles, but 10 square miles is the smallest watershed size with PMP charts in the HMR-51 Publication. No reduction in the PMP is used to reflect the size of the McElroy s Run CCR Impoundment s drainage area. Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis

23 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT PMP PRECIPITATION DISTRIBUTIONS BY ODONNDM DATE 12/21/2015 PROJ. NO. C CHKD. BY BERKEME DATE 12/21//2015 SHEET NO. 2 OF 4 site From the above chart, the 6-hour PMP for a 10 square mile watershed is 27.2 inches. Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis

24 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT PMP PRECIPITATION DISTRIBUTIONS BY ODONNDM DATE 12/21/2015 PROJ. NO. C CHKD. BY BERKEME DATE 12/21//2015 SHEET NO. 3 OF 4 PRECIPITATION continued To perform hydrologic assessments of the PMP event, it is necessary to develop a rainfall mass curve for time intervals less than the 6-hour storm documented previously. The 1973 edition of Design of Small Dams (U.S. Bureau of Reclamation) contains the following chart to distribute precipitation for a 6-hour event. As noted, Zone C is appropriate for areas east of the 105 o meridian, which is the Mountain time zone longitude near Pike s Peak in the Rocky Mountains. The McElroy s Run Impoundment is east of this location, so the use of Zone C is appropriate. Time Ratio to 6-hour amount PMP (inches) 15 minutes hour hours hours hours Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis

25 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT PMP PRECIPITATION DISTRIBUTIONS BY ODONNDM DATE 12/21/2015 PROJ. NO. C CHKD. BY BERKEME DATE 12/21//2015 SHEET NO. 4 OF 4 STORM DESIGN DURATION The West Virginia Dam Safety Regulations state that high-hazard dams West Virginia Title (47 47CSR34 paragraph 7.1.a.2.A) must be designed to meet the Probable Maximum Precipitation for a six hour storm. Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis

26 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2016 PAGE 12 of 12 Attachment 2 Hydrology Calculations Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Updated Calc \Capacity Estimate Writeup docx

27 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2015 Drainage Area Map Hydrology Calculations Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Revised Report and Calc write-up \Temp.docx

28 DRAWING TITLE DRAWN BY: ODONNDM Drainage Area Map NO.: DATE: DWN: CHK: APV: DESCRIPTION: REVISION RECORD ISSUING OFFICE: Pittsburgh 385 E. Waterfront Drive, Homestead, PA PROJECT CLIENT McElroy's Run CCR Impoundment FirstEnergy Corporation Pleasant's Generating Station 800 Cabin Hill Drive Pleasant's County Greensburg, PA West Virginia REVISION 0 CHECKED BY: APPROVED BY: BERKEME SCALE: ISSUE DATE: 1"=1000' 12/24/2015 SHEET NO.: 1 OF 1 GAI FILE NUMBER: Drainage Area Map GAI DRAWING NUMBER: Layout GAI Consultants, Inc.

29 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2015 CN and Time of Concentration Worksheets Hydrology Calculations Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Revised Report and Calc write-up \Temp.docx

30 Runoff Curve Number Project: By: Date: First Energy McElroy's Run CCR Impoundment ODONNDM 12/21/2015 C Checked: Date: Location: BERKEME 12/22/2015 McElroy's Run CCB Impoundment - Upslope Watershed Check one: Present Developed Hydrologic Group Cover Description Table 2-2a Table 2-2b CN Table 2-2c Area Acres Product of CN x Area C B Woods, Fair Woods, Fair TOTALS CN (weighted) = Total Product / Total Area CN 72 Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\ CN

31 Time of Concentration Project: By: Date: McElroy's Run CCB Impoundment ODONNDM 12/21/2015 PMP Dam Routing Checked: Date: Location: BERKEME 12/22/2015 McElroy's Run CCB Impoundment - Upslope Watershed Check one: Present Developed Segment ID Surface Description (Table 3-1)%%%%%%%%%%%%%%.. Manning's Roughness Coefficient, n (table 3-1)%%%%%%%.. Flow Length, L%%%%%%%%%%%%%%%%%%%%%% Two-year 24-hour Rainfall, P 2 %%%%%%%%%%%.%.%%% Land Slope, s%%%%%%%%%%%%%%%%%%...%%%. Travel Time, T t = (0.007*(n*L) 0.8 ) / (P *s 0.4 )%%%%%%%%.. A woods ft 2.55 in 0.14 ft/ft hrs Shallow Concentrated Flow Surface Description (Paved / Unpaved)%%%%%%%%%%%. Surface Description Coefficient, C%%..%.%%%%%%%%%.. Flow Length, L%%%%%%%%%%%%%%%%%%%%%% Watercourse Slope, s%%%%%%%%%.%%%.%...%%%. Average Velocity, V = C*s 0.5 %%%%%%%.%%%%%%%%.. Travel Time, T t = (L) / (3600*V)%%%%%%%%%%%%%%% Channel Flow Segment ID B C Unpaved Unpaved ft ft/ft ft/sec hrs Segment ID D Section Base, b%%%%%%%%%%%%%%%%%%%%%. 0 Section Depth, d%%%%%%%%%%%%%%%%%%%%% 0.5 Section Side Slope, z%%%%%%%%%%%%%%%%%%.. 1 Cross Sectional Flow Area, a = b*d + z*d 2 %%%%%%%%% Wetted Perimeter, p w = b + (2*d)*(z 2 + 1) 0.5 %%%%%%%%% Hydraulic Radius, r = a / p w %%%%%%%%%%%%%%%% Channel Slope, s%%%%%%%%%%%%%%%%%%%%% 0.07 Manning's Roughness Coefficient, n%%%%..%%%%%%%% Average Velocity, V = (1.49*r 2/3 *s 1/2 ) / (n)%%%%%%%%%% ft/sec Flow Length, L%%%%%%%%%%%%%%%%%%%%%% 574 ft Travel Time, T t = (L) / (3600*V)%%%%%%%%%%%%%%% hrs Time of Concentration Sheet Flow T t %%%%%%%%%%%%%%%%%%%%%%. Shallow Concentrated Flow T t %%%%%%%%%%%%%%%. Channel Flow T t %%%%%%%%%%%%%%%%%%%%%. Time of Concentration, T c %%%%%%%%%%%%%%%%% hrs hrs hrs hrs 16 mins Lag Time, T L =0.6*T C hrs 9 mins Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\ TC

32 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2015 Soils Data Hydrology Calculations Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Revised Report and Calc write-up \Temp.docx

33 ' 56'' W 81 17' 6'' W Hydrologic Soil Group Pleasants and Tyler Counties, West Virginia ' 10'' N ' 10'' N 39 21' 4'' N 39 21' 4'' N Map Scale: 1:14,300 if printed on A landscape (11" x 8.5") sheet. N Meters 1200 Feet Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 17N WGS Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey ' 56'' W 81 17' 6'' W /21/2015 Page 1 of 4

34 Hydrologic Soil Group Pleasants and Tyler Counties, West Virginia MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:20,000. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Pleasants and Tyler Counties, West Virginia Survey Area Data: Version 9, Sep 24, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Oct 7, 2011 May 11, 2012 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/21/2015 Page 2 of 4

35 Hydrologic Soil Group Pleasants and Tyler Counties, West Virginia Hydrologic Soil Group Hydrologic Soil Group Summary by Map Unit Pleasants and Tyler Counties, West Virginia (WV612) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI DuC Duncannon silt loam, 8 to 15 percent slopes GaC Gallia silt loam, 8 to 15 percent slopes GpC GpD GpE GpF VaD WnB Gilpin-Upshur complex, 8 to 15 percent slopes Gilpin-Upshur complex, 15 to 25 percent slopes Gilpin-Upshur complex, 25 to 35 percent slopes Gilpin-Upshur complex, 35 to 70 percent slopes Vandalia silt loam, 15 to 25 percent slopes Wheeling-Urban land complex, 0 to 8 percent slopes B % B % C % C % C % C % C % % Totals for Area of Interest % Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/21/2015 Page 3 of 4

36 Hydrologic Soil Group Pleasants and Tyler Counties, West Virginia Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/21/2015 Page 4 of 4

37 SUBJECT FIRST ENERGY MCELROY S RUN CCR IMPOUNDMENT HYDRAULIC CAPACITY ESTIMATE BY ODONNDM DATE 12/22/2015 PROJ. NO. C CHKD. BY BERKEME DATE 1/7/2015 Precipitation Data Hydrology Calculations Z:\Energy\2015\C FE CCR Pleasants Impdmnt\Working Docs\H&H Analysis\Revised Report and Calc write-up \Temp.docx

38 Precipitation Frequency Data Server Page 1 of 4 NOAA Atlas 14, Volume 2, Version 3 Location name: Saint Marys, West Virginia, US* Latitude: , Longitude: Elevation: 645 ft* * source: Google Maps POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PFtabular PFgraphical Maps&aerials Duration 5-min 10-min 15-min 30-min 60-min 2-hr 3-hr 6-hr 12-hr 24-hr 2-day 3-day 4-day 7-day 10-day 20-day 30-day 45-day 60-day PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches) 1 Average recurrence interval (years) ( ) ( ) ( ) ( ) 1.02 ( ) 1.19 ( ) 1.27 ( ) 1.51 ( ) 1.78 ( ) 2.14 ( ) 2.52 ( ) 2.70 ( ) 2.88 ( ) 3.50 ( ) 4.02 ( ) 5.65 ( ) 7.11 ( ) 9.09 ( ) 10.9 ( ) ( ) ( ) ( ) 1.01 ( ) 1.24 ( ) 1.44 ( ) 1.53 ( ) 1.81 ( ) 2.13 ( ) 2.55 ( ) 2.99 ( ) 3.20 ( ) 3.41 ( ) 4.14 ( ) 4.74 ( ) 6.62 ( ) 8.31 ( ) 10.6 ( ) 12.7 ( ) ( ) ( ) ( ) 1.24 ( ) 1.56 ( ) 1.81 ( ) 1.92 ( ) 2.26 ( ) 2.61 ( ) 3.09 ( ) 3.58 ( ) 3.82 ( ) 4.06 ( ) 4.86 ( ) 5.51 ( ) 7.59 ( ) 9.41 ( ) 11.8 ( ) 14.1 ( ) ( ) ( ) 1.02 ( ) 1.42 ( ) 1.80 ( ) 2.10 ( ) 2.23 ( ) 2.62 ( ) 3.02 ( ) 3.53 ( ) 4.07 ( ) 4.32 ( ) 4.57 ( ) 5.41 ( ) 6.09 ( ) 8.30 ( ) 10.2 ( ) 12.8 ( ) 15.1 ( ) ( ) ( ) 1.16 ( ) 1.64 ( ) 2.13 ( ) 2.50 ( ) 2.65 ( ) 3.12 ( ) 3.60 ( ) 4.15 ( ) 4.72 ( ) 4.98 ( ) 5.24 ( ) 6.13 ( ) 6.84 ( ) 9.21 ( ) 11.2 ( ) 13.9 ( ) 16.4 ( ) ( ) 1.02 ( ) 1.27 ( ) 1.81 ( ) 2.38 ( ) 2.81 ( ) 2.99 ( ) 3.53 ( ) 4.07 ( ) 4.65 ( ) 5.25 ( ) 5.51 ( ) 5.77 ( ) 6.68 ( ) 7.41 ( ) 9.87 ( ) 12.0 ( ) 14.7 ( ) 17.3 ( ) ( ) 1.10 ( ) 1.36 ( ) 1.97 ( ) 2.63 ( ) 3.13 ( ) 3.35 ( ) 3.96 ( ) 4.57 ( ) 5.16 ( ) 5.80 ( ) 6.05 ( ) 6.31 ( ) 7.22 ( ) 7.95 ( ) 10.5 ( ) 12.6 ( ) 15.5 ( ) 18.0 ( ) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS) ( ) 1.17 ( ) 1.46 ( ) 2.13 ( ) 2.89 ( ) 3.46 ( ) 3.71 ( ) 4.41 ( ) 5.10 ( ) 5.70 ( ) 6.35 ( ) 6.59 ( ) 6.84 ( ) 7.75 ( ) 8.47 ( ) 11.1 ( ) 13.3 ( ) 16.1 ( ) 18.7 ( ) ( ) 1.26 ( ) 1.58 ( ) 2.34 ( ) 3.23 ( ) 3.91 ( ) 4.21 ( ) 5.03 ( ) 5.84 ( ) 6.45 ( ) 7.11 ( ) 7.33 ( ) 7.55 ( ) 8.44 ( ) 9.14 ( ) 11.8 ( ) 14.0 ( ) 16.9 ( ) 19.6 ( ) ( ) 1.33 ( ) 1.66 ( ) 2.49 ( ) 3.50 ( ) 4.26 ( ) 4.61 ( ) 5.54 ( ) 6.45 ( ) 7.04 ( ) 7.70 ( ) 7.89 ( ) 8.08 ( ) 8.94 ( ) 9.62 ( ) 12.3 ( ) 14.5 ( ) 17.4 ( ) 20.1 ( ) Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top PF graphical You created this PDF from an application that is not licensed to print to novapdf printer ( 1/7/2016

39 Precipitation Frequency Data Server Page 3 of 4 Large scale terrain 2 km Map data 2016 Google Report a map error Large scale map 2 km Map data Report 2016 a map Google error Large scale aerial 2 km Imagery 2016 TerraMetrics Report a map error Back to Top US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service National Water Center 1325 East West Highway Silver Spring, MD You created this PDF from an application that is not licensed to print to novapdf printer ( 1/7/2016