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HomeMy WebLinkAboutNC0038377_Errata_20200505161P synTerra CORRECTIVE ACTION PLAN UPDATE REVISION 1: APRIL 23, 2020 Site Name and Location: Mayo Steam Electric Plant 10660 Boston Road Roxboro, North Carolina 27574 Groundwater Incident No.: Not Assigned NPDES Permit No.: NCO038377 NCDEQ CCR Impoundment Ranking: Low -Risk Date of Report: December 31, 2019 Permittee and Current Duke Energy Progress, LLC Property Owner: 410 South Wilmington Street Raleigh, North Carolina 27601 855-355-7042 Consultant Information: SynTerra Corporation 148 River Street Greenville, South Carolina (864) 421-9999 Latitude and Longitude of Facility: N 36.527423 / W-78.890774 IG 1425 ct Manager r CB/ ICEN��SFo -� SEAE1 ,,9 LG 1328 ct Director TABLES 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 Valuesz Piedmont Background Threshold Value Range 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 10 0.1 1 0.4 4 1 0.4 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 Ng/L NE --- --- --- 5 6 48 Feb-95 Magnesium mg/L NE 1 14 13 1 14 15 1 - 45 Manganese Ng/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 Ng/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 500 85 430 340 130 430 470 50- 1,200 Thallium Ng/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 Ng/mL 0.03^ 0.0004 0.001 0.002 0.0002 0.001 0.003 0.0002 - 0.8640 Vanadium pg/L 0.3* 1 6 6 3 6 4 0.3 - 25.8 Zinc pg/L 1,000 227 12 37 140 15 35 5 - 140 Prepared by: ]HC 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 usinq data from backqround qroundwater samples collected July 2011 to March 2017. z - Updated BNs were calculated using data from backqround qroundwater samples collected April 2010 to December 2018. 3 - Piedmont background threshold value ranges include the Duke Energy calculated 20174 and 2019' background threshold values from 30 Duke Energy facilities located in the Piedmont physiographic region (Allen Steam Station', Belews Creek Steam Station', Buck Steam Station 4, Cape Fear Steam Electric Plant4, Cliffside Steam Station', Dan River Steam Station, Marshall Steam Station', Mayo Steam Electric Plant', Riverbend Steam Station 4, and Roxboro Steam Electric Plant'). --- - 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-CaCO,/L - milligrams calcium carbonate per liter mg-N/L - milligrams nitrogen per liter NE - not established pCi/L - picocunes per liter S.U. - standard units TDS - total dissolved solids TOC - total organic carbon Rev. 1 23 April 2020 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 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 1 700 700 10 10 1* 300 1 50 NE NE 250 500 0.3* 2017 Background Threshold Values (Surficial Flow Zone)' 4.9-6.5 1 19 50 0.1 3 1 385 253 3 25 2 85 1 2019 Background Threshold Values (Surficial Flow Zone )2 4.9-6.9 2 22 50 4 8 2 6,820 395 30 27 3 130 3 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 6 1 1,319 298 1 391 8 430 6 2019 Background Threshold Values (Transition Zone )2 5.6-6.6 1 68 50 1 6 1 1,356 448 1 390 8 430 6 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 0.4 7 1 2,550 519 11 418 18 340 6 2019 Background Threshold Values (Bedrock Flow Zone )2 5.1-7.2 1 97 50 0.4 7 5 3,771 548 17 418 130 470 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 <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 Rev. 1 Page 1 of 3 23 April 2020 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 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 1 700 700 10 10 1* 300 1 50 NE NE 250 500 0.3* 2017 Background Threshold Values (Surficial Flow Zone)' 4.9-6.5 1 19 50 0.1 3 1 385 253 3 25 2 85 1 2019 Background Threshold Values (Surficial Flow Zone )2 4.9-6.9 2 22 50 4 8 2 6,820 395 30 27 3 130 3 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 6 1 1,319 298 1 391 8 430 6 2019 Background Threshold Values (Transition Zone )2 5.6-6.6 1 68 50 1 6 1 1,356 448 1 390 8 430 6 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 0.4 7 1 2,550 519 11 418 18 340 6 2019 Background Threshold Values (Bedrock Flow Zone )2 5.1-7.2 1 97 50 0.4 7 5 3,771 548 17 418 130 470 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 I 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 2 192 <50 <0.025 1<1 I<1 572 11,363 114 1451 19 409 1<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 Rev. 1 Page 2 of 3 23 April 2020 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 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 1 700 700 10 10 1* 300 50 NE NE 250 500 0.3* 2017 Background Threshold Values (Surficial Flow Zone)' 4.9-6.5 1 19 50 0.1 3 1 385 253 3 25 2 85 1 2019 Background Threshold Values (Surficial Flow Zone )2 4.9-6.9 2 22 50 4 8 2 6,820 395 30 27 3 130 3 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 6 1 1,319 298 1 391 8 430 6 2019 Background Threshold Values (Transition Zone )2 5.6-6.6 1 68 50 1 6 1 1,356 448 1 390 8 430 6 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 0.4 7 1 2,550 519 11 418 18 340 6 2019 Background Threshold Values (Bedrock Flow Zone )2 5.1-7.2 1 97 50 0.4 7 5 3,771 548 17 418 130 470 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 I 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 1158 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 1 0.03 <1 <1 97 1 14 1 <1 141 11 73 1 <0.3 Prepared by: PWA Checked by: GRK 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 - 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). - Bold highlighted concentration indicates exceedance of both BTV values. - 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 Rev. 1 Page 3 of 3 23 April 2020 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 SO 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 7 1 2,550 519 11 418 18 340 6 Background Threshold Values (Bedrock Unit) 5.1-7.2 1 97 50 0.4 7 5 3,771 548 17 418 130 470 4 Background Data Set Range (Bedrock Unit); 5.1-7.2 <1 - 1.8 14 - 101 <50 <0.021 - 0.41 <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 <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 15A 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 Rev. 1 23 April 2020 Page 1 of 1