The URL can be used to link to this page

Home My WebLink AboutNC0003468_Annual Report_20171114(� DUKE ENERGY November 14, 2017 Mr Sergei Cherenkov, PhD State of North Carolina Department of Environmental Quality Division of Water Resources Complex NPDES Permitting Unit 1617 Mail Service Center Raleigh, NC 27699-1617 Dan River Combined Cycle Duke Energy Carolinas 900 South Edgewood Road Eden, NC 27288 RECEI°�/t;:+Dr'�, C )EQ1Drip; NOV 17 2017 vvak� .I Pslzy Perm, Section Subject Duke Energy Carolinas, LLC Dan River Combined Cycle Station — NPDES Permit #NC0003468 Ash Basin Working Capacity — Annual Report Dear Mr Sergei As required by Special Condition A (13) in the Dan River Combined Cycle NPDES permit, attached is the Annual Report — Ash Basin Working Capacity, which summarizes the actual free water volume of the Ash Ponds and the physical measurements of the dimensions of the free water volume for your review and file Should you have any questions regarding this submittal or require additional information, please contact Joyce Dishmon at 336-623-0238 or email Joyce Dishmon@duke-encig I certify under penalty of law, that this document and all attachments were prepared under my direction or supervision to accordance with a system designed to assure that qualified personnel properly gather and evaluate the cnformatton submitted Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete I am aware that there are significant penalties for submitting false information, including the possibility of fines and imprisonment for knowing violations SiKc�My, !��arry Sparks GM II — Regulated Stations Dan River Combined Cycle Attachment Cc Joyce Dishmon/Filenet, Sr Env Specialist Dana Newcomb, Lead EHS Field Support amec foster wheeler Memo To: Joyce Dishmon, Henry Taylor From: Chris Jordan, Cedric Ruhl Date: November 1, 2017 Ref: Dan River Primary and Secondary Ash Basins Re: Free Water Storage Volume Duke Energy Carolinas, LLC (Duke) has requested that Amec Foster Wheeler provide an estimate of the Dan River Primary and Secondary Ash Basin working capacity to assist with the National Pollutant Discharge Elimination System (NPDES) permit renewal process Estimate Required Free Water Volume The NPDES permit requires that the Primary and Secondary Ash Basins each have a free water volume (FWV) capacity to store stormwater runoff and 24 hours of plant discharge water For the purposes of this memo the stormwater runoff volume was assumed to consist of runoff from the 10 -year, 24-hour design storm assuming 100 percent of rainfall is converted to runoff (i e a curve number of 100) The Dan River Station no longer sluices material to the Primary or Secondary Ash Basins, therefore, the plant discharge water volume is 0 The drainage area to the Secondary Ash Basin is the Dry Fly Ash Basin and the footprint of the Secondary Ash Basin itself as shown in Figure 1A The drainage area to the Primary Ash Basin is the footprint of the Primary Ash Basin Itself as shown in Figure 1 B The Primary Ash Basin no longer discharges by gravity to the Secondary Ash Basin The required free water volume was calculated as shown in the following table Table 1- Required Free Water Volume Stormwater Runoff Volume 24 -Hour Plant Total Required Total Tributary 10 -Year, 24 -Hour Discharge Water Free Water Basin Stormwater Drainage Area Rainfall Depth Volume Volume Runoff Volume (acres) (in) (acre-feet) (acre-feet) (acre-feet) PnmaryAsh Basin 1 274 510 1165 0 1165 Secondary Ash Basin 1 923 1 10 3923 0 3923 Amec Foster Wheeler Environment & Infrastructure, Inc 14424 Albemarle Point Place Registered in North Carolina Suite 115 Engineering License No F-1253 Chantilly, Virginia 20151 Geology License No C-247 703-488-3700 Dan River Primary and Secondary Ash Basins Free Water Storage Volume Amec Foster Wheeler Project No 7810170870 11/1/2017 Estimate Available Water Storage Volume The available water storage volume was estimated based on topographic survey Information collected in 2014 as shown in Figure 2 Stage -storage relationships for the Primary and Secondary Ash Basins are provided in the following tables Table 2A -Stage -Storage Relationship for Primary Ash Basin Elevation (ft) Surface Area (acrEs) Incremental Storage Volume (acre-feet) Cumulative Storage Volume (acre-feet) 528 740 000 000 529 8 22 781 781 530 9 _3 868 1649 531 982 948 2596 532 1122 1052 3648 Table 213 -Stage -Storage Relationship for Secondary Ash Basin Elevation (ft) Surface Area (acres) Incremental Storage Volume (acre-feet) Cumulative Storage Volume (acre-feet) 515 707 000 000 516 747 727 727 517 737 767 1494 518 814 801 2295 519 834 824 3119 520 852 843 3962 521 868 860 4822 522 885 877 5698 523 915 900 6598 524 9.81 948 7546 525 1160 1071 8617 526 1224 1192 9809 527 1250 1237 11046 528 1? 04 r 1277 12323 52852 1 IS 38 r 687 13009 CCR material has been removed from the Primary Ash Basin after the 2014 survey, therefore, the current storage volume in the Primary Ash Basin is greater than shown in Table 2A Dan River Primary and Secondary Ash Basins Free Water Storage Volume Amec Foster Wheeler Project No. 7810170870 11/1/2017 Compare Required Free Water Volume to Available Water Storage Volume The required free water volume was compared to the available water storage volume as shown in the following table: Table 3 - Summary of Required vs. Available Storage Volume Total Required Available Storage Available Storage Free Water Basin Volume Volume > Total Volume (acre-feet) Required FWV? (acre-feet) Primary Ash Basin 11.65 36.48 yes Secondary Ash Basin 39.23 130.09 yes Conclusions The Primary and Secondary Ash Basins meet or exceed the required free water volume requirements. CCR material will be excavated from the Primary and Secondary Ash Basins during closure of these units which will result in an increase in available storage volume. Attachments Figure 1A — Drainage Area and Flow Path (Dry Fly Ash Basin and Secondary Ash Basin) Figure 1 B - Drainage Area and Flow Path (Primary Ash Basin) Figure 2 — Basin Contours FLOWPATH L=1,669.6 FT 81 0 F FLYS/ BASIN LEGEND MAJOR CONTOUR (I OFT) MINOR CONTOUR (2FT)FLOWPATHPOST-DEVELOPMENT DRAINAGE AREA N 0 100 200 400 600 Feet Data Source: Topographic Data from LDS1. JODW 7010-14-0150 Prepared By: Date JMS 8/31/2016 Checked By: Date RLH 8/31/2016 DAN RIVER ASH PLANT DUKE ENERGY EDEN, NORTH CAROLINA DRAINAGE AREA AND �% /FLOWPATH LEGEND Q POST -DEVELOPMENT DRAINAGE AREA �•••�•FLOWPATH MAJOR CONTOUR (10FT) MINOR CONTOUR (2FT) N 0 100 200 400 600 Feet Data Source: Topographic Data from LDSI. Job #: 7610-14-0150 Prepared By: I Checked By: Date: JMS 9/1/2016 Date: RLH 9/1/2016 DAN RIVER ASH PLANT DUKE ENERGY EDEN, NORTH CAROLINA FIGURE 16 DRAINAGE AREA AND FLOWPATH amec foster wheeler 44