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Home My WebLink AboutNC0038377_04_Mayo_CAP Update 2019_Tables_20191231Corrective Action Plan Update December 2019 Mayo Steam Electric Plant TABLES (CAP Content Section 9) SynTerra Corrective Action Plan Update December 2019 Mayo Steam Electric Plant SynTerra Table ES-1 Summary of Mayo Assessment Documentation Included in Executive Summary Text Corrective Action Plan Update December 2019 Mayo Steam Electric Plant SynTerra Table ES-2 Summary of Mayo Assessment Activities (Through June 2019) Included in Executive Summary Text Corrective Action Plan Update December 2019 Mayo Steam Electric Plant SynTerra Table ES-3 Components of Source Control, Active Remediation, and Monitoring Included in Executive Summary Text TABLE 3-1 SUMMARY OF ONSITE POTENTIAL ADDITIONAL SOURCE FACILITIES CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO NC Evaluated Facility as Source CSA Operational Source Area Rationale Name Area n Schedule Status Material or Capacity for Evaluation CAP Update Coal Ash/NPDES- 140 acres/ Ash Basin Yes NA Inactive permitted waste 6,600,000 tons CAMA unit streams CCR FGD Forward FGD wastewater/ Lined units; constructed Flush No NA Inactive Landfill leachate/ 16.9 acre-feet = within footprint of ash Pond/FGD NPDES permitted 5,506,881 gallons Settling Pond waste streams basin Adjacent to and Coal Storage No To be Operational Coal —30 acres upgradient of ash basin. Pile Area determined To be evaluated separate from CAP Update Gypsum To be Lined unit; currently Storage Pad No determined Operational Synthetic gypsum 1 acre unknown if hydrologically Area connected to ash basin Lined units; not hydrologically connected Low Volume NPDES permitted to ash basin; no record of Ponds No NA NA waste streams 1 acre CCR waste handling; evaluation not required per NCDEQ (Risgaard, July 19, 2019; Appendix A) Prepared by: JAW cneCke(I by: PWA Notes: CSA Schedule - applicable only for units identified in the letter "Final Comprehensive Site Assessment and Corrective Action Plans Approvals for Duke Energy Coal Ash Facilities" (April 5, 2019). CSA Schedule updated by NCDEO (November 13, 2019; Appendix A). CAMA - North Carolina Coal Ash Management Act of 2014 CAP - Corrective Action Plan CCR - Coal Combustion Residuals CSA - Comprehensive Site Assessment FGD - Flue Gas Desulfurization NA - Not applicable NA - not applicable NCDEQ - North Carolina Department of Environmental Quality NPDES - National Pollutant Discharge Elimination System Page 1 of 1 TABLE 4-1 BACKGROUND SOIL SAMPLE SUMMARY CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Soil Boring Depth Range (ft bgs) Number of Sampled Intervals SB-01 (1-14.5) 2 BGSB-02 (4-15) 3 BGSB-03 (4-9) 2 BGSB-04 (4-15) 3 BGSB-05 (4-15) 3 BGSB-08 (4-9) 2 BGSB-09 (4-15) 3 M W-08BR (0.75-26) 2 MW-10BR (0.75-1) 1 MW-12D (1-26) 2 Note: ft bgs - feet below ground surface Prepared by: JAW Checked by: PWA Page 1ofI TABLE 4-2 BACKGROUND VALUES FOR SOIL CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Constituent Reporting Unit PSRG Protection of Groundwater 2018 Background Threshold Values" 2019 Up Updated Background Z Threshold Values Piedmont Background Threshold Value Range pH* S.U. NE 5.2-7.6 4.7-8.3 2.3-9.8 Aluminum mg/kg 110,000 46,946 50,978 25,978 - 81,619 Antimony mg/kg 0.9 0.7 0.6 0.2 - 0.9 Arsenic mg/kg 5.8 4.5 3.9 1.2 - 43.1 Barium mg/kg 580 616 598 122 - 1,063 Beryllium mg/kg 63 1 2 1 -5 Boron mg/kg 45 13 16 14 - 56 Cadmium mg/kg 3.0 0.03 0.6 0.03 - 1.0 Calcium mg/kg NE 4,830 8,769 282 - 8,769 Chloride mg/kg NE 42 312 12 - 423 Chromium mg/kg 3.8 77.4 440.0 20.0 - 440.0 Cobalt mg/kg 0.9 44.2 81.7 27.0 - 81.7 Copper mg/kg 700 124 216 17 - 216 Iron mg/kg 150 82,634 85,345 24,500 - 85,345 Lead mg/kg 270 16 16 34912.0 Magnesium mg/kg NE 47,958 51,829 760 - 51,829 Manganese mg/kg 65 1,894 2,985 370 - 3,388 Mercury mg/kg 1.0 0.1 0.1 0.04 - 0.1 Molybdenum mg/kg 7.1 4.5 12.0 1.8 - 12.0 Nickel mg/kg 130 71 193 9- 237 Nitrate (as N) mg/kg NE 0.33 31.20 0.25 - 31.20 Potassium mg/kg NE 21,421 20,393 427 - 35,600 Selenium mg/kg 1 2.1 2.9 2.9 1.6 - 6.9 Sodium mg/kg NE 833 1,496 338 - 1,500 Strontium mg/kg 1,500 69 95 7 - 200 Sulfate mg/kg 1,438^ 14 362 12 - 437 Thallium mg/kg 0.28 0.41 0.85 0.17 - 2.13 Vanadium mg/kg 350 188 207 42 - 231 Zinc mg/kg 1,200 340 326 61 - 326 Prepared by: JHG Checked by: SRW/PWA Notes: 2018 background threshold values approved by North Carolina Department of Environmental Quality (NCDEQ) on May 23, 2019. ^ - PSRG Protection of Groundwater value was calculated using the equation shown in Section 6 * - Upper and lower threshold values calculated for parameter Background threshold values were calculated using data from background unsaturated soil samples collected February 2015 to July 2017. 2 - Background threshold values were calculated using data from background unsaturated soil samples collected February 2015 to July 2017. s - Piedmont background threshold value ranges include the Duke Energy calculated 20174 and 2019s background threshold values from 10 Duke Energy facilities located in the Piedmont physiographic region (Allen Steam Stations, Belews Creek Steam Stations, Buck Steam Station4, Cape Fear Steam Electric Plant°, Cliffside Steam Stations, Dan River Steam Station4, Marshall Steam Stations, Mayo Steam Electric Plants, Riverbend Steam Station 4, and Roxboro Steam Electric Plants). mg/kg - milligrams per kilogram NE - not established S.U. - standard unit PSRG - preliminary soil remediation goals Page 1 of 1 TABLE 4-3 BACKGROUND VALUES FOR GROUNDWATER CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Constituent Reporting Unit 15A NCAC 02L Standard 2017 Background Threshold Values' 2019 Updated Background Threshold Values Piedmont Background Threshold Value Range3 Surficial Zone Transition Zone Bedrock Zone Surficial Zone Transition Zone Bedrock Zone pH S.U. 6.5 - 8.5 4.9 - 6.5 5.7 - 6.5 5.0 - 7.3 4.9 - 6.9 5.6 - 6.6 5.1 - 7.2 3.6 - 9.0 Alkalinity mg-CaCO3/1- NE 13 302 223 42 302 240 19- 379 Aluminum pg/L NE 566 490 494 566 692 574 100 - 1,238 Antimony pg/L 1* 1 1 1 1 1 1 0.5- 3 Arsenic pg/L 10 1 1 1 2 1 1 0.2-6 Barium pg/L 700 19 78 97 22 68 97 11- 840 Beryllium pg/L 4* 1 1 1 1 1 1 0.06 - 1 Bicarbonate mg-CaCO3/1- NE 13 302 223 23 302 221 19- 388 Boron pg/L 700 50 50 50 50 50 50 50- 177 Cadmium pg/L 2 1 1 1 1 1 1 0.08 - 1 Calcium mg/L NE 3 59 73 13 59 73 4 - 111 Carbonate mg-CaCO3/1- NE 5 5 5 10 10 10 5- 10 Chloride mg/L 250 3 33 43 5 39 41 3 -250 Chromium pg/L 10 3 6 7 8 6 7 1- 26 Chromium (VI) pg/L NE 0.09 1.26 0.40 4.40 1.28 0.36 0.03 - 12.00 Cobalt pg/L 1* 1 1 1 2 1 5 0.09 - 89 Copper pg/L 1,000 2 5 5 4 5 5 0.5 - 17 Fluoride mg/L 2 --- --- --- 0.1 0.3 0.4 0.1- 1.8 Iron pg/L 300 385 1,319 2,550 6,820 1,356 3,771 56 - 37,500 Lead pg/L 15 1 1 1 2 1 1 0- 2 Lithium pg/L NE --- --- --- 5 6 48 Feb-95 Magnesium mg/L NE 1 14 13 1 14 15 1 - 45 Manganese pg/L 50 253 298 519 395 448 548 7- 9,170 Mercury pg/L 1 0.2 0.2 0.05 0.05 0.2 0.2 0.05 - 0.5 Methane pg/L NE 12 2,256 10 273 2,505 42 1- 2,505 Molybdenum pg/L NE 3 1 11 10 1 17 0.5 - 26 Nickel pg/L 100 3 5 5 5 5 6 0.9 - 48 Nitrate + Nitrite mg-N/L NE 1 0.3 1 1 1 1 0.02 -6 Potassium mg/L NE 4 4 7 5 4 11 2- 19 Selenium pg/L 20 1 1 1 1 1 2 0.5- 2 Sodium mg/L NE 5 53 73 8 53 117 6 - 190 Strontium pg/L NE 25 391 418 27 390 418 27 - 2,120 Sulfate mg/L 250 2 8 18 3 8 130 1- 510 Sulfide mg/L NE 0.1 0.1 0.1 0.1 0.1 0.2 0.1- 2.0 TDS mg/L S00 85 430 340 130 430 470 50- 1,200 Thallium pg/L 0.2* 0.2 0.2 0.2 0.2 0.2 0.2 0.1 -0.2 TOC mg/L NE 2 2 1 8 2 1 1- 12 Total Radium pCi/L 5^ 4 9 8 2 35 5 0.5- 35 Total Uranium pg/mL 0.03^ 0.0004 0.0010 0.0020 0.0002 0.0010 0.0026 0.0002 - 0.8640 Vanadium pg/L 0.3* 1.0 5.9 5.7 2.8 5.8 4.4 0.3 - 25.8 Zinc pg/L 1,000 227 12 37 140 15 35 5 - 140 Prepared by: JHG Checked by: SRW/PWA Notes: 2017 background threshold values (BTVs) approved by North Carolina Department of Environmental Quality (NCDEQ) on May 14, 2018. Background threshold values have been rounded to similar levels of precision as 15A North Carolina Administrative Code (NCAC) 02L Standard or Interim Maximum Allowable Concentration (IMAC). ' - BNs were calculated using data from background groundwater samples collected July 2011 to March 2017. 2 - Updated BNs were calculated using data from background groundwater samples collected April 2010 to December 2018. 3 - Piedmont background threshold value ranges include the Duke Energy calculated 2017' and 2019' background threshold values from 10 Duke Energy facilities located in the Piedmont physiographic region (Allen Steam Stations, Belews Creek Steam Stations, Buck Steam Station , Cape Fear Steam Electric Plant, Cliffside Steam Stations, Dan River Steam Station', Marshall Steam Stations, Mayo Steam Electric Plants, Riverbend Steam Station , and Roxboro Steam Electric Plants). --- - BTV was not calculated for constituent. * - Interim Maximum Allowable Concentration (IMAC) of the 15A NCAC 02L Standard, Appendix 1, April 1, 2013. ^ - Federal Maximum Contaminant Level (MCL) pg/L - micrograms per liter pg/mL - micrograms per milliliter mg/L - milligrams per liter mg-CaCOs/L - milligrams calcium carbonate per liter mg-N/L - milligrams nitrogen per liter NE - not established pCi/L - picocuries per liter S.U. - standard units TDS - total dissolved solids TOC - total organic carbon Page 1 of 1 TABLE 4-4 BACKGROUND DATASET RANGES FOR SURFACE WATER CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Constituent Reporting Unit Comparison Criteria Background Range Constituents with iSA NCAC 02B (Class B, C, Water Supply: WS-V)1 Standards pH S.U. 6.0-9.0 6.4 - 7.8 Dissolved Oxygen mg/L >_ 4 1.6 - 10.5 Temperature deg C <_ 32 6.4 - 25.3 Turbidity (Streams) NTU <_ 50 2.9 - 45.2 Arsenic pg/L 10 0.336 j - <1 Arsenic (Dissolved) pg/L acute: 340, chronic: 150 0.526 j - <1 Barium pg/L 1000 22 - 73 Beryllium (Dissolved) pg/L acute: 65, chronic: 6.5 <1 Cadmium (Dissolved )2 pg/L acute: 0.82, chronic: 0.15 <0.1 - <1 Chloride mg/L 230 4.2 - 27 Chromium (III) (Dissolved)z,3 Ng/L acute: 183, chronic: 24 0.900 - <0.975 Chromium (VI) (Dissolved) pg/L acute: 16, chronic: 11 <0.025 - 0.9 Copper (Dissolved )2 pg/L acute: 3.6, chronic: 2.7 0.587 j - 3.8 Fluoride mg/L 1.8 0.0757 j - 0.2 Lead (Dissolved )2 pg/L acute: 14, chronic: 0.54 <1 Mercury pg/L chronic: 0.012 0.0008 - 0.019 j Nickel pg/L 25 0.34 j - 1.2 Nickel (Dissolved )2 pg/L acute:140, chronic: 16 0.342 j - <1 Nitrate + Nitrite mg-N/L 10 0.0035 j - 1.1 Selenium pg/L chronic: 5 <1 Silver (Dissolved )2 pg/L acute: 0.3, chronic: 0.06 <0.3 Sulfate mg/L 250 1.2 - 14 Thallium pg/L 2 0.082 j - <0.2 Total Dissolved Solids mg/L 500 55 - 180 Total Hardness mg/L 100 22.4 - 123 Zinc (Dissolved )2 ug/L acute: 36, chronic: 36 2.178 j - 27 Constituents with USEPA National Recommended Water Quality Criteria Alkalinity mg/L chronic: 20 13.5 - 115 Aluminum pg/L acute: 620, chronic: 300 32 - 3,050 Antimony pg/L 5.6 <1 Iron pg/L 1000 165 B1 - 4,600 Manganese pg/L 100 10 - 1,180 Constituents without 02B or USEPA Criteria Bicarbonate mg-CaCO3/L NE 13.5 - 115 Boron pg/L NE 21.042 j - <50 Cadmium pg/L NE 0.056 j - <1 Calcium mg/L NE 4.34 - 25.2 Carbonate Alkalinity mg-CaCO3/L NE <5 - <20 Chromium pg/L NE 0.422 j - 1.87 Chromium (VI) pg/L NE <0.025 - 0.94 Cobalt pg/L NE 0.383 j - 4.72 Copper pg/L NE 0.731 j - 3.3 Lead pg/L NE <0.2 - <1 Lithium pg/L NE <5 Magnesium mg/L NE 2.26 - 14.6 Methane pg/L NE <10 - 140 Molybdenum pg/L NE 0.092 j - 2.1 Page 1 of 2 TABLE 4-4 BACKGROUND DATASET RANGES FOR SURFACE WATER CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Constituent Reporting Unit Comparison Criteria Background Range Potassium mg/L NE 1.17 - 8.06 Sodium mg/L NE 5.48 - 18.1 Strontium pg/L NE 36 - 205 Sulfide mg/L NE <0.1 - <0.5 Total Organic Carbon mg/L NE 2.4 - 7.6 Total Radium pCi/L NE <1 Total Uranium pg/mL NE <0.00005 Vanadium pg/L NE 0.649 - 5.71 Zinc pg/L NE 2.149 j, B1 - 25 Prepared by: PWA Checked by: ENK Notes: Background ranges represent data collected from August 2014 to May 2018 Background locations, which were part of the evaluation of potential groundwater to surface water impacts, were approved by North Carolina Department of Environmental Quality (NCDEQ). ' 15A NCAC 02B .0101 Class B (Recreation)- Freshwaters protected for primary recreation which includes swimming on a frequent or organized basis and all Class C uses. ' 15A NCAC 02B .0101 Class C (Aquatic Life) = Freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival and wildlife. All samples collected from Bowes Branch (SW-BB1 and SW-BB2) are subject to Class C water quality standards. ' 15A NCAC 02B .0101 WS-V (Water Supply) = Waters protected as water supplies which are generally upstream of and draining to Class WS-IV waters. Suitable for all Class C uses. Based on sample location, samples SW-REF1 and SW-REF2 are subject to WS-V water quality standards. z Standard value dependent on hardness. Calculated hardness dependent metal standards represent most conservative value. Standards are calculated using 25 mg/L hardness, regardless if actual instream hardness values are greater than 25 mg/L. 3 Chromium speciation is not performed for trivalent chromium (Cr(III)). Trivalent values are derived by subtracting hexavalent chromium values from dissolved chromium values. Where a dissolved chromium value is less than the detection limit ("<"), it is considered a whole number for purposes of deriving a trivalent chromium value. Acute - "Compliance with acute instream metals standards shall only be evaluated using an average of two or more samples collected with one hour." Reference 15A NCAC 02B .0211 Chronic - "Compliance with chronic instream metals standards shall only be evaluated using averages of a minimum of four samples taken on consecutive days, or as a 96-hor average." Reference 15A NCAC 02B .0211 < - concentration not detected at or above the adjusted detection limit. B1 - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample was greater than 1OX the concentration in the method blank. Analyte concentration in sample is not affected by blank contamination. deg C - degrees Celsius j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit. Ng/L - micrograms per liter Ng/mL - micrograms per milliliter mg/L - milligrams per liter mg-CaCO3/L - milligrams calcium carbonate per liter mg-N/L - milligram nitrogen per liter NE - not established NTU- Nephelometric Turbidity Unit pCi/L - picocuries per liter S.U. - standard unit Page 2 of 2 TABLE 4-5 BACKGROUND DATASET RANGES FOR SEDIMENT CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Constituent Reporting Unit Background Range pH S.U. 6.4 - 6.8 Aluminum mg/kg 2,610 - 13,000 Antimony mg/kg <0.54 - <9.9 Arsenic mg/kg 0.85 j - <9.9 Barium mg/kg 23.7 - 140 Beryllium mg/kg 0.18 j - 0.76 Boron mg/kg <2.9 - <24.7 Cadmium mg/kg 0.044 j - <1.2 Calcium mg/kg 335 - 2,100 Chloride mg/kg <13 - <517 Chromium mg/kg 13 B -100 B Chromium (III) mg/kg NA Cobalt mg/kg 3.9 - 24 Copper mg/kg 1.9 - 44 Iron mg/kg 7,100 - 55,000 Lead mg/kg 3.7 j - 11 Magnesium mg/kg 410 - 3,500 Manganese mg/kg 122 - 2,600 Mercury mg/kg 0.0096 j - <0.16 Molybdenum mg/kg 0.75 j - <4.9 Nickel mg/kg 2.4 - 9 Nitrate (as N) mg/kg <0.26 - <51.7 Nitrate mg/kg <0.26 - <51.7 Potassium mg/kg 340 - 2,500 Selenium mg/kg 0.65 j - <9.9 Silver mg/kg 0.31 j - <1.3 Sodium mg/kg <280 - <495 Strontium mg/kg 3.2 j - 22 Sulfate mg/kg <13 - <333 Sulfide mg/kg <18.7 j - 47.8 Thallium mg/kg 0.035 j - <9.9 Total Organic Carbon mg/kg 3,100 - 57,200 Vanadium mg/kg 15.1 - 150 Zinc mg/kg 14 - 174 Prepared by: TAH Checked by: ENK Notes• Background ranges represent data collected from May 2015 to May 2018 Background locations, which were part of the evaluation of potential groundwater to surface water impacts, were approved by North Carolina Department of Environmental Quality (NCDEQ). < - concentration not detected at or above the adjusted reporting limit. B - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample is less than 1OX the concentration in the method blank. Analyte concentration in sample could be due to blank contamination. j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit. mg/kg - milligrams per kilogram NA - not available S.U. - standard unit Page 1 of 1 TABLE 5-1 APRIL 2019 WATER LEVEL MEASUREMENTS AND ELEVATIONS CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO NC Well ID Top of Casing (ft NAVD 88) Top of Screen Elevation (ft NAVD 88) Bottom of Screen Elevation (ft NAVD 88) April 2019 Measured Water Level (ft BTOC) 1 April evy Water Elevation (ft NAVD 88) Monitoring Flow Zone ABMW-01 483.81 478.7 468.2 2.50 481.31 Ash ABMW-02 493.90 456.6 451.4 10.51 483.39 Ash ABMW-02BR 493.85 396.2 386.2 10.83 483.02 Bedrock ABMW-02BRL 493.97 335.4 325.4 11.37 482.60 Bedrock ABMW-03 500.17 461.9 456.7 16.84 483.33 Ash ABMW-03S 500.30 447.1 437.1 16.95 483.35 Saprolite ABMW-04X 492.37 441.2 436.2 6.63 485.74 Ash ABMW-04BR 491.61 389.6 380.1 5.96 485.65 Bedrock ABMW-04D 491.50 430.9 425.7 6.02 485.48 Transition Zone AP-06` 488.76 411.4 421.4 6.42 482.34 Ash AP-06-LI52 489.18 415.7 420.7 6.97 482.21 Ash AP-06-1-302 489.18 415.6 420.6 7.03 482.15 Ash AP-06-M152 489.51 440.8 445.8 7.23 482.28 Ash AP-06-M302 489.04 439.5 444.5 6.99 482.05 Ash AP-06-U152 489.52 463.1 468.1 7.30 482.22 Ash AP-06-U302 489.46 463.1 468.1 7.37 482.09 Ash BG-01 540.11 494.9 484.9 23.99 516.12 Bedrock BG-02 542.66 513.8 494.3 30.09 512.57 Transition Zone CCR-101D-BG 521.90 510.7 505.7 10.11 511.79 Transition Zone CCR-101S-BG 519.91 490.8 485.8 20.16 499.75 Surficial (Saprolite) CCR-102BR-BG 531.03 467.9 457.9 21.34 509.69 Bedrock CCR-103BR 489.36 421.9 411.9 13.78 475.58 Bedrock CCR-103D 488.91 442.4 432.4 14.45 474.46 Transition Zone CCR-103S 489.05 465.9 455.9 14.50 474.55 Surficial (Saprolite) CCR-104BR 409.00 368.8 358.8 0.00 409.00 Bedrock CCR-1045 408.85 402.1 397.1 3.90 404.95 Surficial (Saprolite/ Alluvium) CCR-105BR 391.46 354.1 344.1 10.44 381.02 Bedrock CCR-105D 391.18 369.3 364.3 8.95 382.23 Transition Zone CCR-105S 391.07 380.0 375.0 9.77 381.30 Surficial (Saprolite) CCR-106BR 383.13 349.0 339.0 6.90 376.23 Bedrock CCR-107BR 441.22 416.0 406.0 3.85 437.37 Bedrock CCR-108BR 487.41 438.9 428.9 11.06 476.35 Bedrock CCR-109BR 406.41 352.8 337.8 7.91 398.50 Bedrock CPA-113R 518.75 450.7 440.7 23.40 495.35 Bedrock CPA-11) 518.15 485.9 475.9 24.60 493.55 Transition Zone CPA-2BR 524.00 471.2 461.2 24.15 499.85 Bedrock CPA-21) 524.04 497.4 487.4 23.76 500.28 Transition Zone CPA-3BR 520.74 442.7 432.7 7.91 512.83 Bedrock CPA-31) 520.80 502.9 492.9 6.97 513.83 Transition Zone CPA-4BR 540.68 OH OH 118.80 421.88 Bedrock CPA-41) 540.48 511.5 501.5 19.34 521.14 Transition Zone CPA-5BR 535.16 446.5 431.5 12.53 522.63 Bedrock CPA-51) 534.83 481.4 471.4 11.49 523.34 Transition Zone CPA-5S 534.67 511.8 496.8 10.70 523.97 Surficial (Saprolite) CPA-6BR 521.19 OH OH 33.74 487.45 Bedrock CPA-7BR 519.20 OH OH 51.11 468.09 Bedrock CPA-71) 519.12 495.6 485.6 13.84 505.28 Transition Zone CW-01 489.88 470.6 461.1 15.91 473.97 Transition Zone CW-01D 490.96 457.1 447.3 17.36 473.60 Bedrock CW-02 389.00 378.3 368.5 12.38 376.62 Transition Zone CW-02D 389.53 340.8 331.0 15.80 373.73 Bedrock CW-03 437.68 417.7 402.9 14.23 423.45 Transition Zone CW-04 451.31 413.3 408.5 19.80 431.51 Bedrock CW-05 509.60 470.4 465.6 3.67 505.93 Bedrock CW-06 462.83 387.1 382.3 9.51 453.32 Bedrock DEP-1 517.91 OH OH 9.59 508.32 Bedrock DEP-2 562.01 OH OH 12.64 549.37 Bedrock DEP-3 539.29 OH OH 2O.53 518.76 Bedrock FGD-0113R 484.69 346.5 326.5 21.23 463.46 Bedrock Page 1 of 3 TABLE 5-1 APRIL 2019 WATER LEVEL MEASUREMENTS AND ELEVATIONS CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO NC Well ID Top of Casing (ft NAVD 88) Top of Screen Elevation (ft NAVD 88) Bottom of Screen Elevation (ft NAVD 88) April 2019 Measured Water Level (ft BTOC) 1 April 2019 Water Elevation (ft NAVD 88) Monitoring Flow Zone FGD-01D 484.48 451.0 441.0 22.33 462.15 Transition Zone FGD-02BR 487.33 298.2 288.2 38.96 448.37 Bedrock FGD-02D 486.97 448.4 438.4 24.17 462.80 Transition Zone FGD-03BR 485.93 346.0 326.0 23.41 462.52 Bedrock FGD-03D 486.29 442.8 432.8 22.37 463.92 Transition Zone FGD-04BR 487.66 309.1 299.1 25.36 462.30 Bedrock FGD-05BR 475.79 384.3 369.3 33.13 442.66 Bedrock FGD-05D 475.91 419.4 404.4 33.42 442.49 Transition Zone FGD-06BR 479.02 385.9 375.9 33.21 445.81 Bedrock FGD-06D 479.07 447.7 437.7 30.73 448.34 Transition Zone FGD-07BR 483.19 388.8 373.8 27.52 455.67 Bedrock FGD-07D 483.25 424.4 414.4 26.93 456.32 Transition Zone FGD-07S 483.23 444.6 434.6 27.84 455.39 Surficial (Saprolite) FGD-08BR 510.22 271.6 256.6 49.42 460.80 Bedrock FGD-09BR 509.62 358.3 343.3 48.49 461.13 Bedrock FGD-10BR 510.02 400.7 385.7 45.48 464.54 Bedrock FGD-11BR 470.55 324.5 309.5 28.54 442.01 Bedrock FGD-11D 470.42 411.2 396.2 29.91 440.51 Transition Zone FGD-12BR 463.08 351.6 336.6 25.93 437.15 Bedrock FGD-12D 461.85 401.8 386.8 26.16 435.69 Transition Zone FGD-13BR 450.62 308.1 293.1 13.68 436.94 Bedrock FGD-13D 450.03 385.3 370.3 14.49 435.54 Transition Zone FGD-14BR 455.44 271.0 256.0 0.00 455.44 Bedrock LRB-01 503.16 471.8 461.8 1.26 501.90 Bedrock LRB-02 496.38 444.8 434.8 14.00 482.38 Bedrock LRB-03 553.36 501.3 491.3 37.44 515.92 Transition Zone MW-02 461.23 421.1 411.1 24.95 436.28 Bedrock MW-03 384.30 374.1 364.1 6.33 377.97 Alluvium M W-03BR 438.24 367.1 361.9 14.16 424.08 Bedrock M W-04 522.77 483.7 463.7 26.66 496.11 Bedrock M W-05BR 511.40 450.7 445.7 4.76 506.64 Bedrock M W-06BR 463.99 373.7 363.7 10.60 453.39 Bedrock MW-08BR 466.99 405.1 399.9 33.10 433.89 Bedrock MW-08D 466.89 433.8 428.6 33.08 433.81 Transition Zone MW-08S 466.87 441.7 436.7 29.84 437.03 Saprolite M W-09BR 495.39 444.8 434.8 20.87 474.52 Bedrock MW-09BRL 498.56 435.0 425.1 23.11 475.45 Bedrock M W-10BR 513.39 465.8 455.8 11.58 501.81 Bedrock M W-11BR 527.36 438.7 428.6 34.39 492.97 Bedrock MW-12D 588.02 501.5 491.5 27.91 560.11 Transition Zone MW-12S 587.38 547.0 537.0 28.08 559.30 Saprolite M W-13BR 528.83 438.0 428.1 27.10 501.73 Bedrock M W-14BR 520.75 488.9 483.9 16.03 504.72 Bedrock M W-15BR 460.92 408.3 398.3 57.58 403.34 Bedrock M W-16BR 371.30 319.3 309.0 4.72 366.58 Bedrock MW-16D 371.21 340.0 329.8 4.40 366.81 Transition Zone MW-16S 371.11 363.2 360.5 4.96 366.15 Alluvium M W-17BR 490.55 377.1 367.1 29.20 461.35 Bedrock M W-18BR 516.78 418.1 403.1 11.47 505.31 Bedrock MW-18D 516.71 475.1 464.8 11.92 504.79 Transition Zone M W-19BR 495.94 408.8 398.8 6.73 489.21 Bedrock MW-19D 495.81 449.4 438.8 4.12 491.69 Transition Zone M W-103BRL 491.88 152.5 137.5 15.12 476.76 Bedrock MW-103BRM 490.46 262.6 247.6 25.25 465.21 Bedrock MW-104BRL3 410.08 172.0 157.0 NM NM Bedrock MW-104BRM3 410.23 242.0 227.0 NM NM Bedrock M W-105BRL 391.35 153.1 138.1 40.80 350.55 Bedrock MW-105BRM 1 391.14 1 282.4 1 267.4 1 0.05 1 391.09 1 Bedrock M W-107BRL 1 443.32 1 152.5 1 137.5 1 18.90 1 424.42 1 Bedrock Page 2 of 3 TABLE 5-1 APRIL 2019 WATER LEVEL MEASUREMENTS AND ELEVATIONS CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO NC Well ID Top of Casing (ft NAVD 88) Top of Screen Elevation (ft NAVD 88) Bottom of Screen Elevation (ft NAVD 88) April 2019 Measured Water Level (ft BTOC) 1 April 2019 Water Elevation (ft NAVD 88) Monitoring Flow Zone MW-107BRM 441.55 260.7 245.7 39.97 401.58 Bedrock P-01 475.86 UNK UNK 32.75 443.11 Earthen Dam P-01A 475.00 UNK UNK 36.04 438.96 Earthen Dam P-02 458.65 UNK UNK 43.92 414.73 Earthen Dam P-02A 458.62 UNK UNK 17.25 441.37 Earthen Dam P-03 446.99 UNK UNK 51.15 395.84 Earthen Dam P-03A 445.69 UNK UNK 46.07 399.62 Earthen Dam P-04 454.57 UNK UNK 39.79 414.78 Earthen Dam P-04A 454.99 UNK UNK 36.88 418.11 Earthen Dam Notes: * - Abandoned sampling location ' - Manual water levels collected on April 1-2, 2019 1 - Installed in 2018, not sampled 3 - Artesian conditions present BTOC - below top of casing ft - feet NAVD 88 - North American Vertical Datum of 1988 NM - Not Measured OH - Open hole bedrock (no screen) UNK - Unknown See Figures 5-4a through 5-4c for graphical representation of data. Prepared by: PWA Checked by: GRK Page 3 of 3 TABLE 5-2 GROUNDWATER BALANCES SUMMARY CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY CAROLINAS, LLC, ROXBORO, NC Pre- Post- Closure- Modeling Scenario Closure -by -Excavation Decanting Decanting in -Place c .. .. c .. .. c .. .. c .. .. Water Balance -E o� -E of -E of -E of Components 3 Q o o, 3 a o m 3 Q o o, 3 a o m 3 0- o o, 3 a o m 3 0- o o, 3 CL o m LL - � �- � LL - Direct recharge to the 13 29 53 ash basin Direct recharge to the watershed outside of 129 134 137 126 the ash basin Ash basin pond 62 Drainage inside the 4 106 81 131 ash basin' Drainage outside of the 63 50 48 46 ash basin Flow through and under 18 7 8 1 the dam Prepared by: PWA Checked by: RY Notes: ' Drainage includes streams, seeps, ditch, channel, canal, etc. Drainage streams included are depending on the scenario, for example, the pre -decanting scenario includes streams present prior to closure and closure -by excavation includes streams that potentially re-form within the excavated ash basin footprint after closure -by -excavation. Flow in refers to recharge to the groundwater system Flow out refers to discharge from the groundwater system gpm - gallons per minute Page 1 of 1 TABLE 5-3 SURFACE WATER CLASSIFICATION CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Adjacent Surface Water Body Surface Water Classification (15A NCAC 02B .0300) Mayo Reservoir WS-V Crutchfield Branch B Bowes Branch C Prepared by: JAW Checked by: PWA Notes: 1. Class B waters are protected for primary recreation, which includes swimming on a frequent or organized basis and all Class C uses. 2. Class C waters are protected for secondary recreation, fishing, wildlife, fish consumption, aquatic life, agriculture, and other uses suitable for Class C. 3. Class WS-V waters are generally upstream of Class WS-IV waters or waters currently or formerly used by industry for water supply. These waters are also protected for Class C uses. NCAC - North Carolina Administrative Code WS - Water Supply Page 1 of 1 TABLE 6-1 BORON CONCENTRATIONS IN GROUNDWATER BELOW SOURCE AREA CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Boron Boron Number Concentration Concentration Well Beneath Ash of Sample Time Period Range in Range in (Flow Zone) Events of Record Groundwater Overlying Pore (pg/L) Water (pg/L) ABMW-2BR (bedrock) 14 06/2015 - 04/2019 < 50 1 7,980 - 9,200 (� 40' saturated ABMW-2BRL 14 02/2016 - < 501 ash) (bedrock) 04/2019 1,740 - 2,010 ABMW-3S (surficial) 14 04/2014/2019 0 - 1,100 - 1,340 40' saturated ash) ABMW-4D (transition zone) 14 06/2015 - 04/2019 3,040 - 5,090 4,930 - 6,520 (� 60' saturated ABMW-4BR 14 06/2015 - < 501 ash) (bedrock) 04/2019 Prepared by: PWA Checked by: JAW Notes: < — Concentration not detected at or above the adjusted reporting limit. 1 — Concentrations have not been detected at or above the adjusted reporting limit across all sampling events pg/L — micrograms per liter Page 1 of 1 TABLE 6-2 SOURCE AREA INTERIM ACTIONS CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Groundwater and Surface Water Rationale Remedy Component Decanting will lower the hydraulic head within the ash basin, reduce hydraulic gradients and groundwater seepage velocities in and under the Ash Basin ash basin dam, and further limit constituent transport potential. Decanting Decanting will return the groundwater flow system to its approximate condition, prior to construction of the ash basin, with the re- establishment of groundwater flowing toward the historic stream valley and then north. Toe Drain A collection system to capture flow from the ash basin dam engineered Collection System toe drains and route flow back to the ash was installed and is in operation. Source Area Modifications including vegetation removal and regrading/compaction Stabilization and ash basin forebay equalization pipe improvements were completed to mitigate potential future erosion and improve dam site conditions. Prepared by: PWA Checked by: JAW Page 1 of 1 TABLE 6-3 SOIL PSRG POG STANDARD EQUATION PARAMETERS AND VALUES CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Csoil = Cgw [Kd + (Ow + eaH�)/Pb]df Inorganic Parameter Definition Default Values Units Parameters CSo;i Calculated source concentrations for soil NA mg/kg C9"' Applicable groundwater target 15A NCAC 02L mg/L concentration: 15A NCAC 02L Standard Standard df Dilution factor 201 unitless Kd Soil -water partition coefficient for Constituent Specific4 L/kg inorganics (range) Ow Water -filled soil porosity - vadose soils 0.32 Lwater/Lsoi, Oa Air filled soil porosity - vadose soils 0.133 Lair/LSoii Pb dry bulk density 1.62 kg/L Henry's law constant -dimensionless H' where: H' = Henry's law constant (atm - Constituent Specific3,5 unitless m3/mole) x conversion factor of 41 Prepared by: PWA Checked by: LWD Notes: 1 - Default value from Soil Screening Guidance: Technical Background Document (USEPA, 1996) z - Site specific value (Murdoch et al., 2019). Effective porosity represents unconsolidated material. 3 - DEQ default value appropriate for North Carolina 4 - Constituent Specific- Soil water partition coefficients (Kd) were obtained from the Groundwater Quality Signatures for Assessing Potential Impacts from Coal Combustion Product Leachate (EPRI, 2012). Sulfate Kd ranges from 0.1 to 2.1, based on sands/sediments and a pH range of 4.6 to 7.2 5 - a value of 0 is used for sulfate NA - Not applicable NCAC - North Carolina Administrative Code mg/kg - milligrams per kilogram mg/L - milligrams per liter L/kg - liters per kilogram Lwater/Lsoii - volume of water filled spaces per volume of soil Lair/Lsoi, - volume of air filled spaces per volume of soil kg/ - kilogram per liter Page 1 of 1 TABLE 6-4 SUMMARY OF UNSATURATED SOIL ANALYTICAL RESULTS CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameter pH Arsenic Barium Boron Chromium* Cobalt Iron Manganese Molybdenum Strontium Sulfate Vanadium Reporting Units S.U. mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg PSRG Protection of Groundwater NE 5.8 580 45 3.8 0.9 150 65 7.1 1500 1438^ 350 2018 Background Threshold Values' 5.2-7.6 4.5 616 13 77 44.2 82,634 1,894 4.5 69 14 188 2019 Background Threshold Valuesz 4.7-8.3 3.9 598 16 440 82.0 85,345 2,985 12.0 95 362 207 Sample ID Sample Collection Date Analytical Results BGSB-02 (4-5) 07/18/2017 6.1 0.49 j,B 55 M <2.5 M 3.3 M 6.1 16,000 M 190 <2 M 4.8 <12 36 BGSB-02 (9-10) 07/18/2017 6.3 0.53 B 80 <2.7 34 8.8 15,000 210 lj 10 <11 42 BGSB-02 (14-15) 07/18/2017 6.2 0.55 B 34 <2.8 1.4 3.5 7,900 120 <2.2 10 <11 15 BGSB-03 (4-5) 07/18/2017 6.2 0.58 B 140 <13 36 21 43,000 570 <10 30 <11 100 BGSB-03 (8-9) 07/18/2017 7.0 0.34 j,13 150 <12 1.3 j 16 25,000 770 <9.8 28 <11 13 BGSB-04 (4-5) 07/18/2017 6.8 1.6 B 69 <3.2 12 17 27,000 120 0.81j 8.9 <13 94 BGSB-04 (9-10) 07/18/2017 6.6 0.6 B 210 <3.1 3.4 24 22,000 310 <4.9 17 <13 69 BGSB-04 (14-15) 07/18/2017 6.7 0.58 j,6 270 <3.2 10 24 42,000 130 <2.6 49 <14 160 BGSB-05 (4-5) 07/18/2017 6.2 2.6 B 41 <2.9 40 17 27,000 240 1 j 9.8 <12 130 BGSB-05(9-10) 07/18/2017 5.8 2 B 53 <5.3 20 12 36,000 280 1.2j 10 <12 120 BGSB-05 (14-15) 07/18/2017 7.7 0.34 j,13 250 <5.7 6.1 38 31,000 1,200 <4.5 54 <13 110 BGSB-08 (4-5) 07/18/2017 7.7 0.34 j,13 120 <2.6 4.6 4.7 11,000 200 0.6 j 46 <11 30 BGSB-08 (8-9) 07/18/2017 7.1 0.33 j,13 83 <4.2 630 24 25,000 410 0.53 j 19 <11 45 BGSB-09 (4-5) 07/18/2017 6.8 3.5 B 350 <5.8 61 81 46,000 450 <12 60 <12 140 BGSB-09 (9-10) 07/18/2017 6.7 1.8 B 520 <13 440 37 69,000 2,900 <10 69 <12 110 BGSB-09 (14-15) 07/18/2017 6.8 1.6 B 490 <13 70 34 69,000 3,100 1.9 j 38 <11 170 MW-03BR (0.8-1.2) 02/05/2015 5.0 <3 57.6 <3 11.3 5.4 8,480 327 <6 5.4 <299 16 MW-03BR (14.75-15) 02/05/2015 8.4 <2.5 74.4 <25.4 1.5 j 4.3 7,750 468 <5.1 9.6 <255 7.6 MW-07BR (1-2) 04/23/2015 5.6 <5.1 21.5 <12.8 4.1 <5.1 7,320 28 <2.6 2 j <257 12.8 MW-08BR (0.75-1.25) 02/11/2015 6.0 <3.2 147 <63.4 62.2 21.3 24,700 1,230 <12.7 13.2 <309 50.6 MW-08BR(25.5-26) 02/11/2015 7.4 <2.7 193 31j 419 32.9 31,300 933 <10.9 33.6 <272 75.8 MW-10BR (0.75-1.0) 02/23/2015 6.3 1.4 81.8 13.6 j 41.9 12.4 18,600 527 < 0.57 9.4 NA 35.1 MW-11BR (0-2) 04/14/2015 5.2 <7.5 43.1 <18.8 22.6 6.4 j 52,900 53 <3.8 18.6 <354 208 MW-11BR (30-32) 04/15/2015 7.4 <5.3 179 <13.1 2.3 40.9 44,000 212 <2.6 23.7 <257 191 MW-12D (1-2) 04/26/2015 4.9 3.6j 19.6 27.4 43.6 <6 31,200 22 <3 <3 <302 61 MW-12D (25-26) 04/27/2015 5.9 <6 67.4 9.8j 3.2 6 11,900 395 <3 <3 <301 8.2 MW-13BR (0-2) 04/12/2015 4.9 <6.5 72.9 <16.3 6.1 <6.5 19,600 83 0.42 j 1.8 <334 32.4 MW-15BR (0.5-1) 05/09/2015 5.2 <6.2 64.6 <15.5 10.4 3.9 j 15,600 108 <3.1 11.2 <305 27.1 PSB-01 04/08/2019 4.7 3.9 110 <3.4 29 9.6 19,000 150 3.5 15 330 57 PSB-02 04/08/2019 4.9 0.71 j 110 <3.7 9.8 7.9 19,000 320 <2.9 21 63 36 PSB-03 04/08/2019 6.3 0.38j 120 <3 35 11 22,000 490 <2.4 35 15 40 PSB-04 04/08/2019 5.5 0.87 72 <3 8.8 4.7 24,000 320 <2.4 18 15 38 PSB-05 04/09/2019 5.0 0.91 200 <6 65 17 37,000 350 <2.4 40 69 81 PSB-06 04/09/2019 4.7 0.74 34 <3 11 1.7 20,000 56 <2.4 8.1 100 28 PSB-07 04/09/2019 5.5 1.1 72 <2.7 6.4 6.8 22,000 260 <2.2 31 63 34 PSB-08 04/09/2019 5.3 1.3 73 <3 12 5 20,000 300 <2.4 9.7 6.7j 40 PSB-09 04/09/2019 7.3 0.49j 50 <2.9 3.6 1.6 13,000 84 <2.4 16 <12 18 PSB-10 04/09/2019 4.9 3.5 88 <3.1 14 3.9 30,000 160 1.9j 12 90 52 PSB-11 04/09/2019 5.4 1.3 64 <2.6 13 10 13,000 710 <2.1 7.6 <12 22 PSB-12 04/09/2019 4.8 1 84 <3 6.2 8.4 15,000 210 <2.4 12 14 15 PSB-13 04/09/2019 4.9 1.5 120 <2.8 8.3 5 21,000 200 <2.3 15 62 31 PSB-14 04/09/2019 5.6 <0.58 48 <2.9 1.6 3 15,000 250 <2.3 9.4 16 22 PSB-15 04/09/2019 5.3 0.48j 49 <2.6 7.5 4.4 7,100 130 <2.1 12 15 16 PSB-16 04/09/2019 5.8 0.8 75 <2.8 6.3 5.8 20,000 480 <2.3 38 130 29 PSB-17 04/09/2019 5.3 1 120 <2.9 6.8 7.3 18,000 280 <2.3 24 52 23 PSB-18 04/09/2019 6.4 0.26j 110 <2.6 66 9.5 18,000 600 <2.1 18 <12 41 PSB-19 04/09/2019 5.1 1.7 84 <3.1 60 7.7 30,000 190 <2.5 14 8.9j 59 PSB-20 04/09/2019 6.2 0.58 j 380 <3 57 22 27,000 2,100 <2.4 28 56 59 Page 1 of 2 TABLE 6-4 SUMMARY OF UNSATURATED SOIL ANALYTICAL RESULTS CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameter pH Arsenic Barium Boron Chromium* Cobalt Iron Manganese Molybdenum Strontium Sulfate Vanadium Reporting Units S.U. mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg PSRG Protection of Groundwater NE 5.8 580 45 3.8 0.9 150 65 7.1 1500 1438^ 350 2018 Background Threshold Values' 5.2-7.6 4.5 616 13 77 44.2 82,634 1,894 4.5 69 14 188 2019 Background Threshold Values2 4.7-8.3 3.9 598 16 440 82.0 85,345 2,985 12.0 95 362 207 Sample ID Sample Collection Date Analytical Results PSB-21 04/09/2019 5.7 0.37j 26 <2.6 20 2.7 9,400 34 <2.1 4.5 68 14 PSB-22 04/09/2019 5.0 0.94 56 <2.7 50 5.6 18,000 150 <2.1 8.6 33 32 PSB-23 04/09/2019 5.1 1.7 91 <2.6 33 7.8 14,000 150 <2.1 8.6 62 35 PSB-24 04/08/2019 5.3 0.58 61 < 2.3 7.8 1.8 5,000 24 < 1.9 2.7 < 11 6.8 PSB-25 04/08/2019 5.4 0.25j 66 <2.6 10 6.7 12,000 370 <2.1 12 <12 22 PSB-26 04/08/2019 5.1 1 69 <2.9 19 6.3 17,000 370 <2.3 15 19 35 PSB-27 04/08/2019 4.9 1.3 78 <2.7 9.4 12 12,000 590 <2.2 11 14 22 PSB-28 04/08/2019 5.4 0.4j 44 <3.4 8.6 9.2 5800 M 110 M <2.7 10 M 210 18 PSB-29 04/08/2019 5.4 0.61 50 <3.1 16 4.6 8,200 210 <2.5 10 <14 17 PSB-30 04/08/2019 4.9 1.4 75 <2.9 14 3 13,000 120 <2.3 14 25 31 SB-01 (1-2) 03/04/2015 6.3 1.2j 50 9.6 15.7 3.7 12,400 104 <0.7 6 <362 28.3 SB-01 (13.5-14.5) 03/04/2015 5.5 1.2 j 62 <15.9 <1.6 8.9 8,490 678 <3.2 8.3 <312 17.8 SB-02 (0.5-2) 03/03/2015 5.3 1.9 66 16.3 j 12.9 6.4 18,300 365 < 0.8 4.3 < 392 44.8 SB-02 (11.0-12.5) 03/03/2015 6.0 1.5 31 7.8 10.8 1.6 10,300 69 0.89 1.1 <309 23.8 SB-03 (5-6) 03/04/2015 8.6 0.64j 55 5.7 20.7 4.9 8,070 348 1.1 11 <272 15 SB-03 (17-18.5) 03/04/2015 4.9 1.6 51 12.9 35.6 5.2 18,100 120 <0.75 4.4 <360 38.4 SB-05 (1-2) 03/04/2015 6.0 1.8 47 <17 <1.7 2.8 8,280 406 <3.4 4.2 <346 6.8 SB-05 (2.3-3.3) 03/04/2015 5.9 1.1 41 < 13.5 < 1.4 1.7 6,670 393 < 2.7 5.2 < 271 5.9 SB-05 (8-9) 03/04/2015 6.5 1 j 22 <13.7 <1.4 2.2 5,790 195 0.36 j 3.1 <272 4.8 SB-06 (1-2) 03/04/2015 5.9 1.2j 55 2.9j 0.74 2.5 3,920 192 <0.64 4.1 <309 2.7 SB-07 (1-2) 05/07/2015 5.1 < 5.8 69 <14.5 11.4 5.9 9,460 693 <2.9 5.7 <286 17.6 SB-07 (4.5-7.5) 05/07/2015 6.4 <6 16 <15 8.2 <6 6,040 226 <3 2.9 j <300 8.2 Notes: ' - Background threshold values were calculated using data from background groundwater samples collected February 2015 to July 2017. 2 - Background threshold values were calculated using data from background groundwater samples collected February 2015 to July 2017. 0 - Bold highlighted concentration indicates value is greater than applicable regulatory standard (PSRG POG). 0 - Bold highlighted concentration indicates value is greater than both background threshold value where there is no regulatory standard, or background threshold values are greater than regulatory standard. 0 - Highlighted concentration indicates value within range of background threshold values for constituents where there is no regulatory standard, or background threshold values are greater than regulatory standard. * - NC PSRG for POG is for hexavalent chromium, soil analytical is for total chromium. ^- Calculated PSRG for POG; Using NCDEQ IHSB Preliminary Soil Remediation Goals companion notes (February 2018). < - Concentration not detected at or above the adjusted reporting limit. B - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample is less than 1OX the concentration in the method blank. Analyte concentration in sample could be due to blank contamination. j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit. M - Matrix spike / matrix spike dup failure. mg/kg - milligrams per kilograms NE - Not Established PSRG POG - Preliminary Soil Remediation Goals for the Protection of Groundwater (POG); NCDEQ Inactive Hazardous Sites Branch (IHSB) Preliminary Soil Remediation Goals table (February 2018) S.U. - Standard Unit Prepared by: PWA Checked by: GRK Page 2 of 2 TABLE 6-5 SEEP CORRECTIVE ACTION STRATEGY CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS LLC, ROXBORO, NC Regulatory Approximate Average Seep ID Program General Location Present Flow Seep Corrective Action Strategy (cfs) Seep collection system in place and continuously operational. Flow collected and routed to NPDES Constructed toe drain (west toe drain) permitted wastewater treatment system. Basin source control measures (e.g., decanting, S-01 SOC to Crutchfield Branch 0.01 dewatering, basin closure) my cause changes in seep flow. No additional corrective action for this location is anticipated. Seep collection system in place and continuously operational. Flow collected and routed to NPDES S-02 SOC Constructed toe drain (east toe drain) 0.005 permitted wastewater treatment system. Basin source control measures (e.g., decanting, to Crutchfield Branch dewatering, basin closure) my cause changes in seep flow. No additional corrective action for this location is anticipated. Adjacent to east toe drain in rip rap S-02B SOC at toe of east side groin of ash basin NM Basin decanting as part of basin closure predicted to eliminate seep. dam Ridge east of east toe drain, flowing S-08 SOC northwest in small channel to NM Basin decanting as part of basin closure predicted to eliminate seep. Crutchfield Branch At bottom of hillside; seep to small S-10 SOC channel, flowing northwest into NM Basin decanting as part of basin closure predicted to eliminate seep. Crutchfield Branch Notes: cfs - cubic feet per second SOC - Special Order by Consent NM - Not measured. Flow is diffuse along the ground surface or within areas of rip rap and accurate flow measurements are not able to be collected. Prepared by: JAW Checked by: PWA Page 1 of 1 TABLE 6-6 MEANS OF GROUNDWATER CONSTITUENTS - JANUARY 2018 TO APRIL 2019 CORRECTIVE ACTIVE PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameters pH Arsenic Barium Boron Chromium (VI) Chromium Cobalt Iron Manganese Molybdenum Strontium Sulfate Total Dissolved Solids Vanadium Reporting Units S.U. pg/L pg/L lag/L pg/L pg/L pg/L pg/L pg/L lag/L pg/L mg/L mg/L pg/L 15A NCAC 02L Standard 6.5-8.5 30 700 700 NE 30 1* 300 50 NE NE 250 500 0.3* 2017 Background Threshold Values (Surficial Flow Zone)' 4.9-6.5 1 19 50 0.09 3 1 385 253 3 25 2 85 1.0 2019 Background Threshold Values (Surficial Flow Zone)z 4.9-6.9 2 22 50 4.40 8 2 6,820 395 10 27 3 130 2.8 Background Data Set Range (Surficial Flow Zone)3 5.2-6.4 <1 - 1.5 8 - 19 <50 0.04 - 4.40 <1 - 7 <1 - 2 108 - 6820 11 - 395 <1 - 10 12 - 27 0.87 -2 26 - 110 <0.3 - 2.8 2017 Background Threshold Values (Transition Zone)' 5.7-6.5 1 78 50 1.26 6 1 1,319 298 1 391 8 430 5.9 2019 Background Threshold Values (Transition Zone )2 5.6-6.6 1 68 50 1.28 6 1 1,356 448 1 390 8 430 5.8 Background Data Set Range (Transition Zone)3 5.6-6.6 <1 13 - 71 <50 <0.025 - 0.96 <1 - 10 <1 48 - 1130 18- 248 <1 - 2 83 - 391 0.96 -8 81 - 450 <0.3 - 5.9 2017 Background Threshold Values (Bedrock Flow Zone)' 5.0-7.3 1 97 50 0.40 7 1 2,550 519 11 418 18 340 5.7 2019 Background Threshold Values (Bedrock Flow Zone)z 5.1-7.2 1 97 50 0.36 7 5 3,771 548 17 418 130 470 4.4 Background Data Set Range (Bedrock Flow Zone)3 5.1-7.2 <1 - 1.8 14 - 101 <50 <0.025 - 0.47 <1 - 20 <1 - 7 11 - 3,260 5 - 648 <1 - 27 131 - 430 0.21 - 140 66 - 510 <0.3 - 4.6 Sample ID Flow Zone Means Results Background Locations BG-01 Bedrock 5.4 <1 85 <50 0.39 <1 <1 94 9 <1 173 0.3 112 4.1 BG-02 Transition Zone 6.4 <1 42 <50 <0.025 2 <1 164 104 <1 296 5 304 4.4 CCR-102BR-BG Bedrock 6.2 <1 22 <50 0.25 2 <1 26 218 6 227 93 420 0.8 MW-12D Transition Zone 6.0 <1 16 <50 0.78 1 <1 105 23 <1 92 1 93 0.7 MW-12S Shallow 5.7 <1 14 <50 0.06 1 <1 499 90 0.4 17 1.7 49 1.2 MW-13BR Bedrock 6.9 <1 19 <50 0.03 3 5 1,167 296 2 324 16 288 0.3 MW-14BR Bedrock 6.6 <1 18 <50 0.03 <1 1 89 86 5 176 9 193 2.5 At or Within the Waste Boundary Locations ABMW-01 Ash Pore Water 7.8 292 552 5,300 0.03 <1 3 2,310 794 259 2,044 28 340 29.1 ABMW-02 Ash Pore Water 9.0 947 66 8,532 0.03 <1 <1 39 65 1408 938 36 388 0.7 ABMW-02BR Bedrock 7.4 3 110 <50 <0.025 <1 <1 1,221 226 18 1,132 12 334 <0.3 ABMW-02BRL Bedrock 7.5 3 74 <50 <0.025 <1 <1 1,806 345 3 2,226 0.2 292 <0.3 ABMW-03 Ash Pore Water 6.7 172 223 1,954 0.025 <1 <1 7,564 644 32 1,484 35 322 0.4 ABMW-03S Shallow 5.1 0.9 28 1,320 <0.025 1 2 1,037 287 <1 77 0.4 98 0.5 ABMW-04X Ash Pore Water 7.0 111 454 5,470 <0.025 0.6 0.5 5,820 1,443 226 2,437 75 453 2.0 ABMW-04D Transition Zone 6.3 22 894 3,242 <0.025 0.9 6 53,940 6,452 12 1,682 1 524 9.0 ABMW-04BR Bedrock 7.6 2 114 <50 <0.025 <1 <1 812 469 10 1,998 45 318 <0.3 CCR-103S Shallow 5.4 <1 115 613 NM <1 <1 NM NM 1 NM 63 218 NM CCR-103D Transition Zone 5.5 <1 104 1,573 NM <1 <1 NM NM <1 NM 113 305 NM CCR-103BR Bedrock 5.4 <1 114 2,603 NM 1 <1 NM NM <1 NM 185 413 NM CCR-104S Shallow 6.0 <1 35 267 NM 1 2 NM NM 0.8 NM 27 183 NM CCR-104BR Bedrock 7.0 <1 26 <50 NM <1 <1 NM NM 4 NM 135 543 NM CCR-105S Shallow 5.8 <1 51 510 NM <1 2 NM NM <1 NM 20 198 NM CCR-105D Transition Zone 6.2 <1 30 810 NM <1 1 NM NM 3 NM 17 230 NM CCR-105BR Bedrock 6.5 <1 5 894 NM <1 <1 NM NM 2 NM 15 318 NM CCR-108BR Bedrock 6.4 <1 23 <50 NM <1 <1 NM NM 5 NM 20 275 NM MW-104BRL Bedrock 7.2 <1 29 <50 0.03 <1 <1 287 86 2 967 55 417 <0.3 Page 1 of 3 TABLE 6-6 MEANS OF GROUNDWATER CONSTITUENTS - JANUARY 2018 TO APRIL 2019 CORRECTIVE ACTIVE PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameters pH Arsenic Barium Boron Chromium (VI) Chromium Cobalt Iron Manganese Molybdenum Strontium Sulfate Total Dissolved Solids Vanadium Reporting Units S.U. pg/L pg/L lag/L pg/L pg/L pg/L pg/L pg/L lag/L pg/L mg/L mg/L pg/L 15A NCAC 02L Standard 6.5-8.5 10 700 700 NE 10 1* 300 50 NE NE 250 500 0.3* 2017 Background Threshold Values (Surficial Flow Zone)' 4.9-6.5 1 19 50 0.09 3 1 385 253 3 25 2 85 1.0 2019 Background Threshold Values (Surficial Flow Zone)z 4.9-6.9 2 22 50 4.40 8 2 6,820 395 10 27 3 130 2.8 Background Data Set Range (Surficial Flow Zone)3 5.2-6.4 <1 - 1.5 8 - 19 <50 0.04 - 4.40 <1- 7 <1- 2 108 - 6820 11 - 395 <1 - 10 12 - 27 0.87 -2 26 - 110 <0.3 - 2.8 2017 Background Threshold Values (Transition Zone)' 5.7-6.5 1 78 50 1.26 6 1 1,319 298 1 391 8 430 5.9 2019 Background Threshold Values (Transition Zone )2 5.6-6.6 1 68 50 1.28 6 1 1,356 448 1 390 8 430 5.8 Background Data Set Range (Transition Zone)3 5.6-6.6 <1 13 - 71 <50 <0.025 - 0.96 <1 - 10 <1 48 - 1130 18- 248 <1- 2 83 - 391 0.96 -8 81 - 450 <0.3 - 5.9 2017 Background Threshold Values (Bedrock Flow Zone)' 5.0-7.3 1 97 50 0.40 7 1 2,550 519 11 418 18 340 5.7 2019 Background Threshold Values (Bedrock Flow Zone)z 5.1-7.2 1 97 50 0.36 7 5 3,771 548 17 418 130 470 4.4 Background Data Set Range (Bedrock Flow Zone)3 5.1-7.2 <1 - 1.8 14 - 101 <50 <0.025 - 0.47 <1 - 20 <1 - 7 11 - 3,260 5 - 648 <1 - 27 131 - 430 0.21 - 140 66 - 510 <0.3 - 4.6 Sample ID Flow Zone Means Results At or Within the Waste Boundary Locations (Continued) MW-104BRM Bedrock 7.8 0.9 19 <50 0.15 2 <1 34 28 6 694 38 307 2.2 MW-105BRM Bedrock 7.3 2 30 <50 0.03 <1 <1 969 421 3 458 30 365 0.2 Between Waste Boundary and Compliance Boundary CCR-106BR Bedrock 7.3 <1 25 61 NM 2 <1 NM NM 4 NM 225 500 NM CCR-107BR Bedrock 6.4 <1 53 1,143 NM <1 <1 NM NM 3 NM 52 250 NM MW-02 Bedrock 5.9 <1 60 <50 <0.025 <1 3 823 923 1 197 18 203 1.0 MW-03 Shallow 5.9 <1 54 1,049 0.18 <1 <1 17 1,224 <1 314 23 195 <0.3 MW-04 Bedrock 6.4 <1 8 <50 0.07 1 <1 46 175 3 124 38 210 0.9 Near or Beyond the Compliance Boundary Upgradient or Sidegradient to the Ash Basin CW-01D Bedrock 6.9 <1 <5 <50 0.06 <1 <1 27 13 22 183 3 204 1.2 CW-05 Bedrock 6.7 <1 54 <50 <0.025 <1 <1 517 696 <1 169 7 278 <0.3 CW-06 Bedrock 6.6 <1 42 <50 <0.025 <1 <1 1,574 1,360 3 325 37 496 <0.3 MW-05BR Bedrock 7.0 <1 35 <50 <0.025 1 <1 6,758 1,800 1 225 2 402 <0.3 MW-08BR Shallow 6.3 <1 18 <50 0.03 1 <1 174 233 3 360 39 440 1.1 MW-09BRL Bedrock 7.1 <1 29 <50 0.04 <1 <1 211 491 5 203 12 300 1.9 MW-10BR Bedrock 6.2 <1 <5 <50 0.11 <1 <1 14 44 <1 203 87 298 2.0 MW-18D Transition Zone 6.2 <1 <5 <50 0.03 <1 <1 49 7 <1 160 37 264 1.5 MW-18BR Bedrock 7.1 2 92 <50 <0.025 <1 <1 572 1,363 14 451 19 409 <0.3 MW-19D Transition Zone 6.7 <1 59 <50 <0.025 <1 <1 1,794 1,010 <1 358 61 510 <0.3 MW-19BR Bedrock 6.8 <1 58 <50 <0.025 <1 <1 1,342 1,356 <1 437 58 596 <0.3 Page 2 of 3 TABLE 6-6 MEANS OF GROUNDWATER CONSTITUENTS - JANUARY 2018 TO APRIL 2019 CORRECTIVE ACTIVE PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameters pH Arsenic Barium Boron Chromium (VI) Chromium Cobalt Iron Manganese Molybdenum Strontium Sulfate Total Dissolved Solids Vanadium Reporting Units S.U. pg/L pg/L lag/L pg/L pg/L pg/L pg/L pg/L lag/L pg/L mg/L mg/L pg/L 15A NCAC 02L Standard 6.5-8.5 10 700 700 NE 10 1* 300 50 NE NE 250 500 0.3* 2017 Background Threshold Values (Surficial Flow Zone)' 4.9-6.5 1 19 50 0.09 3 1 385 253 3 25 2 85 1.0 2019 Background Threshold Values (Surficial Flow Zone)z 4.9-6.9 2 22 50 4.40 8 2 6,820 395 10 27 3 130 2.8 Background Data Set Range (Surficial Flow Zone)3 5.2-6.4 <1 - 1.5 8 - 19 <50 0.04 - 4.40 <1- 7 <1- 2 108 - 6820 11 - 395 <1 - 10 12 - 27 0.87 -2 26 - 110 <0.3 - 2.8 2017 Background Threshold Values (Transition Zone)' 5.7-6.5 1 78 50 1.26 6 1 1,319 298 1 391 8 430 5.9 2019 Background Threshold Values (Transition Zone )2 5.6-6.6 1 68 50 1.28 6 1 1,356 448 1 390 8 430 5.8 Background Data Set Range (Transition Zone)3 5.6-6.6 <1 13 - 71 <50 <0.025 - 0.96 <1 - 10 <1 48 - 1130 18 - 248 <1- 2 83 - 391 0.96 -8 81 - 450 <0.3 - 5.9 2017 Background Threshold Values (Bedrock Flow Zone)' 5.0-7.3 1 97 50 0.40 7 1 2,550 519 11 418 18 340 5.7 2019 Background Threshold Values (Bedrock Flow Zone)z 5.1-7.2 1 97 50 0.36 7 5 3,771 548 17 418 130 470 4.4 Background Data Set Range (Bedrock Flow Zone)3 5.1-7.2 <1 - 1.8 14 - 101 <50 <0.025 - 0.47 <1 - 20 <1 - 7 11 - 3,260 5 - 648 <1 - 27 131 - 430 0.21 - 140 66 - 510 <0.3 - 4.6 Sample ID Flow Zone Means Results Downgradient of the Ash Basin - Wells Used in COI Management Matrix CCR-109BR Bedrock 7.2 1.0 43 <50 NM <1 <1 NM NM 3 NM 290 650 NM CW-02 Transition Zone 5.2 <1 93 720 0.08 <1 <1 15 109 <1 192 37 132 <0.3 CW-02D Bedrock 7.0 <1 25 273 0.31 2 <1 67 59 2 370 72 322 1.1 CW-03 Transition Zone 6.5 <1 16 <50 0.06 <1 <1 101 12 <1 305 17 356 1.8 CW-04 Bedrock 5.9 <1 29 1 <50 0.20 <1 <1 53 <5 <1 144 26 158 1.1 MW-03BR Bedrock 6.9 <1 43 <50 <0.025 <1 <1 396 596 1 398 11 622 0.3 MW-16BR Bedrock 7.6 <1 14 <50 <0.025 <1 <1 1,497 337 21 138 1 177 <0.3 MW-16D Transition Zone 7.0 <1 <5 <50 0.13 <1 <1 73 49 5 170 7 143 0.7 MW-16S Shallow 5.9 <1 75 167 0.03 <1 <1 97 14 <1 141 11 73 <0.3 Notes• ' - Background threshold values were calculated using data from background groundwater samples collected July 2011 to March 2017. Z - Background threshold values were calculated using data from background groundwater samples collected April 2010 to December 2018. 3 - Background data set range from background groundwater samples collected June 2015 to December 2018. Background threshold values have been rounded to similar levels of precision as 15A North Carolina Administrative Code (NCAC) 02L Standard or Interim Maximum Allowable Concentration (IMAC). Bold text - comparison criteria used for each constituent 0 - Bold highlighted concentration indicates exceedance of the 15A NCAC 02L .0202 Standard or the IMAC. (Effective date for 15A NCAC 02L .0202 Standard and IMAC is April 1, 2013). 0 - Bold highlighted concentration indicates exceedance of both BTV values. 0 - Highlighted concentration indicates value within range of background threshold values for constituents where there is no regulatory standard, or background threshold values are greater than regulatory standard. For wells with datasets containing fewer than four valid results, the most recent valid sample data was used. Means were calculated for wells with four or more valid sample results. Sample results were excluded from calculations: a) if turbidity >10 NTU (for constituents other than boron) b) for unusable data (RO qualified) c) if a result was non -detect at a reporting limit (RL) greater than the normal laboratory RL * - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April 1, 2013. < - Concentration not detected at or above the adjusted reporting limit. pg/L - micrograms per liter mg/L - milligrams per liter NE - not established NM - not measured S.U. - Standard unit Prepared by: PWA Checked by: GRK Page 3 of 3 .1 ... — .C1 .M—..iit.li.9 ■ 4 Flow L. N—b—f-11,G-1. ith t—t ,be, p —R.U.—I. f COI. for Corrective Action Evalua tion Pietlmon[ Maximum Mean wells porting 03L or IMAC lane Statistically yMIYO Steam Elril Plant Concentration No, Groundwater Than Criterion N . . . . dd f— if g,..t:, th..comparative -it.- in all c—tit...t. f Dd Bg-d Value �kg—�d —kg.— V.— C--=iGreater m.d/li... id.ufthM the the ..u,u,it Criterion Background Range Byo,d Compliance E.—d.— R.U.0 Beyond Compliance . O.,— Range Range Boundary Boundary TComparative c Flow Zone 2017 ' 201g TABLE 6-8 JULY 2018 - JULY 2019 BORON CONCENTRATIONS NEAR OR BEYOND COMPLIANCE BOUNDARY - DOWNGRADIENT OF ASH BASIN CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Q3-2018 Q4-2018 Q1-2019 Q2-2019 Q3-20193 Boron Boron Boron Boron Boron Well ID Location Relevant to Compliance Boundary Sample Date Concentration Sample Date Concentration Sample Date Concentration Sample Date Concentration Sample Date Concentration (µg/L) (µg/L) (µg/L) (µg/L) (µg/L) CCR-109BR1 ^210-ftinside CB - - 10/2/2018 < 50 1/9/2019 <50 - - 7/9/2019 <50 CW-02 —122-ftinside CB 7/16/2018 952 11/7/2018 661 1/8/2019 407 4/2/2019 421 7/2/2019 1642 CW-02D2 —123-ft inside CB 7/17/2018 263 11/7/2018 211 - - 4/2/2019 244 - - CW-032 at CB 7/17/2018 <50 11/8/2018 <50 4/10/2019 <50 CW-042 at CB 7/17/2018 <50 11/8/2018 <50 4/10/2019 <50 MW-03BR2 at CB 7/17/2018 1 <50 11/8/2018 1 <50 - 4/10/2019 <50 MW-16BR —642-ftbeyond CB 7/18/2018 <50 11/6/2018 <50 1/8/2019 <50 4/2/2019 <50 7/2/219 <50 MW-16D —643-ft beyond CB 7/18/2018 <50 11/6/2018 <50 1/8/2019 <50 4/2/2019 <50 7/2/2019 <50 MW-16S —644-ft beyond CB 7/18/2018 164 11/6/2018 98 1/8/2019 50 4/2/2019 100 7/2/2019 117 Prepared by: PWA Checked by: JAW Notes: 1 Well is part of the Federal Coal Combustion Residual (CCR) Monitoring program. z Well sampled semi-annually in 2019 per approved Interim Monitoring Plan. 3 Appendix C provides data through June 2019 (2Q2019). Data for July 2019 is provided on this table for comparison purposes. `- approximately <- concentration not detected at or above the reporting limit µg/L - micrograms per liter CB - Compliance Boundary TABLE 6-9 SUMMARY TREND ANALYSIS RESULTS FOR GROUNDWATER MONITORING WELLS CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Within the Waste Boundary Between the Waste Boundary and Compliance Boundary Near or Beyond the Compliance Boundary Overall Flow Zone Plume Trend Well ID Boron Concentration Trend in Well Well ID Boron Concentration Trend in Well Well ID Boron Concentration Trend in Well Surficial Zone ABMW-03S Stable CCR-103S Stable MW-16S Stable Stable CCR-104S Stable CCR-105S Stable MW-03 No Trend Transition Zone ABMW-04D Stable Stable CW-02 Decreasing Decreasing LCCR-103D CR-105D Stable CW-03 Non -Detect MW-16D Non -Detect Bedrock Zone ABMW-02BR Non -Detect CCR-103BR Increasing CCR-109BR Non -Detect CCR-104BR Non -Detect ABMW-02BRL Non -Detect CCR-105BR Stable CW-02D Stable Stable CCR-106BR Non -Detect CW-04 Non -Detect ABMW-04BR Non -Detect CCR-107BR Decreasing MW-03BR Non -Detect CCR-108BR Non -Detect MW-16BR Non -Detect MW-02 Non -Detect Increasing Distance from Source 311 Prepared by: PWA Checked by: JAW Notes: 1. Ash pore water wells ABMW-1 and ABMW-3 exibit a stable boron concentration trend. Ash pore water well ABMW-2 shows no statistically significant trend. 2. Summary of results and trends are presented for samples collected from January 2018 - July 2019. 3. Trend results are presented when at least four samples were available and frequency of detection as greater than 50%. Statistically significant trends are reported at the 90% confidence level. 4. Variability Index (VI) is calculated as: the (maximum - minimum) / median concentration and is calculated using detected concentrations only. Values less than 1 indicate low variability in the dataset. Page 1 of 1 TABLE 6-10 WATER SUPPLY WELL ANALYTICAL RESULTS SUMMARY CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC ium Chrom) Total Analytical Parameter pH Arsenic Barium Boron (VI Chromium Cobalt Iron Manganese Molybdenum Strontium Sulfate Dissolved Vanadium Solids Reporting Units S.U. pg/L pg/L pg/L pg/L pg/L pg/L pg/L pg/L pg/L pg/L mg/L mg/L pg/L 15A NCAC 02L Standard 6.5-8.5 10 700 700 NE 10 1* 300 50 NE NE 250 500 0.3* Impacted/ Unimpacted Comments Background Threshold Values (Bedrock Unit)' 5.0-7.3 1 97 50 0.40 1 2,550 519 11 418 18 340 5.7 Background Threshold Values (Bedrock Unit)z 5.1-7.2 1 97 50 0.36 7 5 3,771 548 17 418 130 470 4.4 Background Data Set Range (Bedrock Unit)' 5.1-7.2 <1 - 1.8 14 - 101 <50 <0.025 - 0.47 <1 - 20 <1 -7 11 - 3,260 5 - 648 <1 - 27 131 - 430 0.2 - 140 66 - 510 <0.3 - 4.6 SynTerra Sample ID Sample Analytical Results Map ID MY-03 (Duke) 03/10/2015 NM <1 74 <50 NA <5 <1 1,680 23 <1 469 65 260 2.4 Unimpacted MY-2000 MY-03 (Vendor) 03/10/2015 5.7 <10 70 <100 <20 <10 <5 1,750 21 <10 436 60 293 3.0 Unimpacted Northwest and sidegradient of the ash basin. Low exceedance value for strontium. Strontium exceedances possible from natural source. MY-03 (Vendor) 08/19/2015 5.6 <0.5 60 <5 0.13 0.6 <0.5 <50 8 <0.5 391 56 226 <1 Unimpacted MY-05 (Duke) 05/04/2015 NM <1 61 <50 NA 5 <1 1,300 508 3.4 673 5 340 3.2 Unimpacted MY-5 Northwest and sidegradient of the ash basin. Low exceedance value for strontium. Strontium exceedances possible from natural source. MY -OS (Vendor) 05/04/2015 7.1 <5 55 <50 <0.03 <5 <5 953 517 <5 621 6 349 <10 Unimpacted MY-07(Duke) 09/01/2015 NM <1 32 <50 NA <5 <1 <10 <5 3.6 113 1 110 2.4 Unimpacted MY-2014 All COIs are below comparative criteria. MY-07 (Vendor) 09/01/2015 6.1 <0.5 30 <5 0.63 0.9 <0.5 <50 0.8 3.8 106 3 88 2.5 Unimpacted Northwest and sidegradient of the ash basin. Low exceedance value for MY-2015 MY-1000 01/18/2017 7.0 0.2 44 <25 0.05 <0.5 <0.1 83.1 68 14.8 474 12 152 <0.3 Unimpacted strontium. Strontium exceedances possible from natural source. Molybdenum within range of background values for the area. MY-2012 MY-1001 01/17/2017 6.3 <0.1 9 <25 1.2 2 <0.1 163 5 <0.5 92 <2 93 2.2 Unimpacted All COIs are below comparative criteria. MY-2011 MY-1002 01/17/2017 6.0 <0.1 <0.3 <25 2 2 <0.1 81 <0.5 <0.5 <0.5 2 47 <0.3 Unimpacted All COIs are below comparative criteria. MY-2008 MY-1003 04/12/2017 6.4 0.2 20 <25 <0.025 <0.5 0.2 504 586 <0.5 107 16 237 0.4 Unimpacted South and upgradient of the ash basin. Low exceedance value for manganese and within range of background values for the area. North of the ash basin. Hydraulically disconnected from ash basin by MY-1000 MY-1004 01/18/2017 7.6 0.1 <0.3 <25 0.14 <0.5 <0.1 <50 <0.5 1.1 1 48 485 Unimpacted natural groundwater divides. Low exceedance value for vanadium. Vanadium exceedance possible from natural source. MY-2003-RA MY-2003-RAW 07/10/2017 6.3 <0.1 150 <25 0.09 <0.5 <0.1 51 6 1 262 2 121 0.5 Unimpacted All COIs are below comparative criteria. MY-2013-RA MY-2013-RAW 07/10/2017 6.0 <0.1 16 <25 0.28 <0.5 <0.1 1,830 7 <0.5 109 2 107 1.5 Unimpacted All COIs are below comparative criteria. MY-2016-RA MY-2016-RAW 07/10/2017 6.2 <0.1 122 <25 0.69 1 <0.1 <50 11 <0.5 336 2 231 0.9 Unimpacted All COIs are below comparative criteria. Notes: Background threshold values (BTVs) have been rounded to similar levels of precision as SSA North Carolina Administrative Code (NCAC) 02L Standard or Interim Maximum Allowable Concentration (IMAC). 0 - Bold highlighted concentration indicates exceedance BTV from April 2017 or December 2018, whichever is greater. 0 - Bold highlighted concentration indicates exceedance in between 2017 and 2019 background values when both background values are greater than 02L Standard. Reference Figure 5-7 for water supply well locations Bold text - Constituent concentration exceeds applicable comparison criteria. ' - Background threshold values were calculated using data from background groundwater samples collected July 2011 to March 2017 z - Background threshold values were calculated using data from background groundwater samples collected April 2010 to December 2018 3 - Background data set range from backgound groundwater samples collected June 2015 to December 2018. * - Interim Maximum Allowable Concentrations (IMACs) of the SSA NCAC 02L Standard, Appendix 1, April 1, 2013 < - Concentration not detected at or above the adjusted reporting limit. pg/L - Micrograms Per Liter mg/L - Milligrams Per Liter NA - Not analyzed NM - Not measured S.U. - standard units Prepared by: PWA Checked by: JHC Page 1 of 1 M c m N d u E A d L � to c a d m U. C, E in a L 7 G E a 0 0 ILL m c 0 r 0 E TABLE 6-11 CONFIRMATION MONITORING PLAN ELEMENTS CORRECTIVE ACTION PLAN UPDATE MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Confirmation Monitoring Plan (CMP) Post -Closure Monitoring Plan (PCMP) Implemented 30 days after CAP Approval Implemented after completion of ash basin closure activities CMP Groundwater Well Monitoring Network (background, downgradient of ash basin) IN BG-1' CCR-105D MW-3 BG-2' CCR-105S MW-3BR CCR-101D-BG' CCR-106BR MW-12D' CCR-IO1S-BG' CCR-107BR MW-12S' CCR-102-BR-BG' CCR-108BR MW-13BR' CCR-103BR CCR-109BR MW-16BR CCR-103D CW-2 MW-16D CCR-103S CW-2D MW-16S CCR-104BR CW-3 MW-104BRL CCR-104S CW-4 MW-104BRM CCR-105BR MW-2 MW-105BRM PCMP Groundwater Well Monitoring Network (background, downgradient of ash basin) A PCMP will be implemented at the Site in accordance with G.S. 130A-309.214(a)(4)k.2 after completion of ash basin closure activities. CMP Groundwater Quality3 PCMP Groundwater Quality (Semi -Annual Sampling Frequency) (Sampling frequency to be determined) Boron Calcium Nitrate + Nitrite Alkalinity Chloride Potassium Parameters and sampling frequency to be included in the PCMP in Aluminum Ferrous Iron Sodium accordance with G.S. 130A-309.214(a)(4)k.2 when submitted. Bicarbonate Alkalinity Magnesium Total Organic Carbon CMP and PCMP Groundwater Field Parameters Water Level Specific Conductivity Temperature PH Oxidation Reduction Potential Dissolved Oxygen CMP Review (Annual Reporting) 1) Summary of annual groundwater monitoring results 2) Evaluation of statistical concentration trends 2) Comparison of observed concentrations to model predictions 3) Evaluation of 02L compliance 4) Recommend plan adjustments, if applicable CMP Duration 30 days after CAP approval, the CMP will be implemented at the Site and will continue until there is a total of three years of data confirming COIs are below applicable Standards at or beyond the compliance boundary, at which time a request for termination of CMP sampling will be filed with NCDEQ. If applicable standards are not met, the CMP will continue and transition to post -closure monitoring if necessary. PCMP Review (Annual Reporting) 1) Summary of annual groundwater monitoring results 2) Evaluation of statistical concentration trends 2) Comparison of observed concentrations to model predictions 3) Evaluation of 02L compliance 4) Recommend plan adjustments, if applicable At a frequency no greater than 5 years: 1) Update background analysis 2) Confirm Risk Assessment assumptions remain valid 3) Verify model results, update if needed PCMP Duration After ash basin closure and following ash basin closure certification, a PCMP will be implemented at the Site for a minimum of 30 years in accordance with G.S. 130A-309.214(a)(4)k.2. Early termination: If groundwater monitoring results are below applicable standards for three years, Duke Energy to request termination of corrective action in accordance with G.S. 130A-309.214(a)(3)b. If groundwater monitoring results are above applicable standards, continue groundwater monitoring and evaluate annually thereafter. ' Approved background groundwater monitoring location 2 Geochemically non -reactive constituent (i.e., conservative corrective action COI) that best depicts the areal extent of the plume; monitors plume stability and physical attenuation 3 Parameters are subject to change based on additional data and investigation Italicized parameters - parameters for general water quality to evaluate monitoring data quality Wells indicated in red will have geochemical sondes placed to monitor changing geochemical conditions Page 1 of 1