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HomeMy WebLinkAboutRevised - Mayo BTV GW Tech Memo_20170816TECHNICAL MEMORANDUM Date: August 16, 2017 File: 1026.105 To: Kimberlee Witt (Duke Energy) Cc: Kathy Webb (SynTerra�t, From: Jerry Wylie (SynTerra) Subject: Background Threshold Vfor Groundwater Mayo Steam Electric Plant - Roxboro, NC An updated background groundwater dataset was provided to the North Carolina Department of Environmental Quality (NCDEQ) for Mayo Steam Electric Plant (Mayo) on May 26, 2017. Additionally, the revised Statistical Methods for Developing Reference Background Concentrations for Groundwater and Soil at Coal Ash Facilities (statistical methods document) (HDR Engineering, Inc. and SynTerra Corporation, May 2017) was provided to NCDEQ. On July 7, 2017, NCDEQ provided a response letter (Zimmerman to Draovitch, July 7, 2017) for each Duke Energy coal ash facility that identified soil and groundwater data appropriate for inclusion in the statistical analysis to determine background threshold values (BTVs) for both media. As outlined in the NCDEQ July 7, 2017 letter, Duke Energy is required to provide BTVs for both media within 30 days from receipt of the NCDEQ letter for facilities submitting Comprehensive Site Assessments (CSAs) by October 31, 2017, and 60 days from receipt of the NCDEQ letter for all other facilities. BTVs for soil are provided under separate cover. The revised background groundwater dataset provided to NCDEQ on May 26, 2017 addressed comments provided in a letter by NCDEQ (Zimmerman to Draovitch, April 28, 2017). NCDEQ requested Duke Energy collect at least 10, rather than the previously planned eight, valid samples from background monitoring wells prior to determination of BTVs for constituents within each flow system. For groundwater datasets with less than 10 valid samples available for determination of BTVs, no formal upper tolerance limit (UTL) statistics could be run and the provisional BTV (PBTV) for a constituent and groundwater flow system was computed to be either: ,47 The highest value, or ,07 If the highest value is above an order of magnitude greater than the geometric mean of all values, then the highest value should be considered an outlier and removed from further use and the PBTV is computed to be the second highest value. NCDEQ requested that the updated background groundwater dataset exclude data from the background data set due to one or more of the following conditions: P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH MEMO\ Mayo\ Groundwater\ Final\ Mayo - GW BTV MEMO_FINAL.docx Background Threshold Values for Groundwater August 16, 2017 Mayo Steam Electric Plant Page 2 of 3 0 Sample pH is greater than or equal to 8.5 standard units (S.U.) unless the regional DEQ office has deteremined an alternate background threshold pH for the site; 47 Sample turbidity is greater than 10 Nephelometric Turbidity Units (NTUs); `7 Result is a statistical outlier identified for background sample data collected through second quarter 2017; ,67 Sample collection occurred less than a minimum 60 days between sampling events; and 0 Non-detected results are greater than 2L/IMAC. Additional site-specific requirements related to background groundwater dataset for Mayo groundwater as outlined in the July 7, 2017 NCDEQ letter have been incorporated into the groundwater background dataset. This technical memorandum summarizes the revised background groundwater datasets and statistically determined BTVs. Statistical determinations of BTVs were performed in accordance with the revised Statistical Methods for Developing Reference Background Concentrations for Groundwater and Soil at Coal Ash Facilities (statistical methods document) (HDR Engineering, Inc. and SynTerra Corporation, May 2017). GROUNDWATER BACKGROUND DATA The current background monitoring well network consists of wells installed within three flow zones — surficial, transition zone, and bedrock. Well locations are presented on Figure 1. Background datasets provided to NCDEQ on May 26, 2017 were revised based on input from NCDEQ in the July 7, 2017 letter. The revised background datasets for each flow system used to statistically determine naturally occurring concentrations of inorganic constituents in groundwater are provided in Table 1. The following sections summarize the refined background datasets along with the results of the statistical evaluations for determining BTVs. 411 .14 Is) GIN One well, MW -12S, monitors background groundwater quality within the surficial (saprolite) flow zone. In the July 7, 2017 letter, NCDEQ retained MW -12S in the background dataset. Eleven samples have been collected from MW -12S since June 2015. Samples collected less than 60 days between sampling events, statistical outliers, and invalid data have been omitted from use in statistical determinations which has resulted in six valid samples for the surficial flow zone. Additional samples will be collected from MW -12S to achieve the minimum requirement of 10 valid samples to determine BTVs. The surficial flow zone background dataset is presented in Table 1. PBTVs for constituents within the surficial flow zone were computed to be either the maximum value, or, if the maximum value was above an order of magnitude greater than the geometric mean of all values, the second highest value. PBTVs for the surficial flow system are provided in Table 2. Additional analytical data will be submitted to the NCDEQ Regional P:\Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH MEMO\ Mayo\ Groundwater\ Final\ Mayo - GW BTV MEMO_FINAL.docx Background Threshold Values for Groundwater August 16, 2017 Mayo Steam Electric Plant Page 3 of 3 Office if received and processed in sufficient time for review prior to the preparation of the updated CSA report. TRANSITION ZONE Two wells, BG -02 and MW -121), monitor background groundwater quality within the transition zone. NCDEQ indicated in the July 7, 2017 letter that these two transition zone background wells were retained for use in development of BTVs. The transition zone background groundwater dataset meets the minimum requirement of 10 samples for all constituents except radionuclides (radium -226, radium -228, uranium -233, uranium -234, uranium -236, and uranium -238). Table 1 presents the revised background dataset for the transition zone. PBTVs for radionuclides were computed to be either the maximum value, or, if the maximum value was above an order of magnitude greater than the geometric mean of all values, the second highest value. BTVs were calculated for all remaining constituents monitored within the transition zone using formal UTL statistics. PBTVs and BTVs for the transition zone are presented in Table 2. BEDROCK Three wells - BG -01, MW-13BR, and MW-14BR - monitor background groundwater quality within the fractured bedrock. In the July 7, 2017 letter, NCDEQ recommended that a fourth well (MW-10BR) be removed from the background dataset. Additionally, NCDEQ identified four samples collected from BG -01 and two samples collected from MW-13BR that were collected Jess than 60 days between sampling events and are not appropriate for use in statistical determinations. Prior to statistical determinations, the background bedrock dataset was re -screened for outliers to adjust for the removal of MW-10BR from the dataset. A revised background dataset including updated outliers is presented in Table 1. The background bedrock dataset satisfies the minimum requirement of 10 samples to use formal UTL statistics to derive BTVs for each constituent monitored within fractured bedrock. BTVs for fractured bedrock are presented in Table 2. LIST OF FIGURES Figure 1 Background Groundwater Sample Locations - Mayo Steam Electric Plant LIST OF TABLES Table 1 Background Groundwater Results Through April 2017 - Mayo Steam Electric Plant Table 2 Groundwater Background Threshold Values - Mayo Steam Electric Plant P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH MEMO\ Mayo\ Groundwater\ Final\ Mayo - GW BTV MEMO_FINAL.docx Background Threshold Values for Groundwater August 16, 2017 Mayo Steam Electric Plant FIGURE P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 72017\BTV TECH MEMO \ Mayo \ Groundwater \ Final \ Mayo - GW BTV MEMO_FINAL.docx Background Threshold Values for Groundwater August 16, 2017 Mayo Steam Electric Plant TABLES P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 72017\BTV TECH MEMO \ Mayo \ Groundwater \ Final \ Mayo - GW BTV MEMO_FINAL.docx TABLE 1 BACKGROUND GROUNDWATER RESULTS THROUGH APRIL 2017 MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameter pH Turbidity Alkalinity Aluminum Antimony Arsenic Barium Beryllium Bicarbonate Boron Cadmium Calcium Carbonate Chloride Chromium (VI) Chromium Cobalt Copper Iron Reporting Units S.U. NTUs mg/L ug/L ug/L ug/L ug/L ug/L mg/L ug/L ug/L mg/L mg/L mg/L ug/L ug/L ug/L ug/L ug/L ISA NCAC 02L Standard 6.5-8.5 NE NE NE 1. 10 700 4* NE 700 2 NE NE 250 10 10 1* 1000 300 Sample ID Sample Collection Date Field Parameters Analytical Results Surficial MW -12S 09/10/2015 5.8 6.31 13 98 <1 <1 19 <1 13 <50 <1 1.77 <10 3.1 --- 3.23 1.02 <1 108 MVV -12S 12,102120.15 S7 6-.9 12 1" <4 <1 16 F-1 4-2 <50 <4 3.56 H70 33 0:043 7,17 <1 <4 336 MW -12S 01/07/2016 5.8 9.89 11.1 220 <1 <1 11 <1 11.1 <50 <1 1.96 <5 3.1 0.038 1.43 <1 <1 178 MW -12S 04/06/2016 5.8 7.42 10.2 566 <1 <1 12 <1 10.2 <50 <1 1.19 <5 3.3 0.058 <1 <1 <1 338 MW -12S 07/11/2016 4.9 9.82 12.8 392 <1 <1 13 <1 12.8 <50 <1 2.89 <5 2.9 0.045 <1 <1 1.9 385 MW -145 SB 9-24 93 284 -k <1 42 <-k 9:5 FSB « 4:56 <5 3-2 04-6 F1 <1 E1 27-0 MW -12S 11/04/2016 5.6 9.12 9.2 200 <1 <1 11 <1 9.2 <50 <1 1.14 Bl 15 3.1 0.088 <1 <1 1.08 245 MW -12S 63 9,97 13 324 <1 <1 8 .4 13 .50 <1 232 15 2.2 9:96 <1 <1 2.22 327 MW -12S 02/01/2017 6.5 8.53 238 361 <1 1-79 11 <1 23:8 <50 <1 787 2 <5 B36 S:7 1.61 1-.65 9:4b 3240 Transition Zone <0.5 <5 64.8 B --- --- <50 <0.08 --- --- 32.6 B --- 10.2 __ ___ ___ <5 67.7 --- --- <50 c0.08 --- --- 32.9 --- 7.5 -- <5 312 c0.5 <5 61.5 --- --- <50 <0.08 --- --- 32.6 --- <5 --- <5 152 <0.5 <5 53.4 --- --- <50 <0.08 --- --- 35.3 --- 5.9 -- <5 460 <0.5 <5 60.2 --- --- <50 <0.08 --- --- 33.3 --- 6 --- <5 759 BG -02 04/10/2013 6.3 8.5 --- 226 <1 <1 66 --- --- <50 <1 --- --- 28 --- <5 --- <5 646 BG -02 07/09/2013 6.4 8.08 --- 412 <1 <1 69 --- --- <50 <1 --- --- 30 --- <5 --- <5 1130 BG -02 11/13/2013 6.4 9.5 --- 384 <1 <1 62 --- --- <50 <1 --- --- 29 --- <5 --- <5 841 BG -02 04/01/2014 6.4 7.5 --- 316 <1 <1 71 --- --- <50 <1 --- --- 28 --- <5 --- <5 943 BG -02 07/18/2014 6.4 7.71 --- 355 <1 <1 65 --- --- <50 <1 --- --- 30 --- <5 --- <5 1010 BG -02 11/12/2014 6.3 5.33 --- 233 <1 <1 61 --- --- <50 <1 --- --- 30 <5 --- <5 647 BG -02 04/13/2015 6.3 7.09 259 136 <1 <1 54 <1 259 <50 <1 57 <5 28 --- <5 <1 <5 435 BG -02 07/07/2015 6.5 8.51 225 193 <1 <1 54 <1 225 <50 <1 56.1 <5 30 --- <5 <1 <5 467 BG -02 9/11/2015 6.4 6.88 220 82 <1 <1 50 <1 220 <50 <1 50.6 <10 32 --- 4.05 <1 <1 244 BG -02 12/09/2015 6.4 5.24 257 M1 <100 <0.5 <0.5 60 <0.2 257 <50 <0.08 57.2 M1 c5 29.7 <0.03 <0.5 B <0.5 <1 450 BG -G2 6.4 3:98 263 80 <1 <1 58 <4 263 FSB <1 S7,3 F5 33 <0:03 F1 <1 1-21 474 BG -02 04/04/2016 6.4 2.71 303 65 <1 <1 65 <1 303 <50 <1 59.2 <5 30 <0.03 <5 <1 <5 585 BG -02 07/13/2016 6.2 3.4 302 58 <1 <1 59 <1 302 <50 <1 59.9 <5 30 <0.03 <5 <1 <5 484 SG -B2 6,7 2A 257 15-1 a4 <1 59 F4 2si7 FSB <1 S" FS 33 F0$3 <4 <1 F4 553 BG -02 11/02/2016 6.3 5.07 240 59 <1 <1 48 <1 240 <50 <1 51.3 <5 34 c0.03 <1 <1 <1 213 BG -02 01/30/2017 6.6 9.68 228 82 <1 <1 43 <1 228 <50 <1 50 B2 <5 33 0.055 <1 <1 <1 184 MW -12D 06/24/2015 6.2 4.02 53 184 1.63 <1 26 <1 53 <50 <1 12.6 <10 4 --- <1 4,37 <1 326 MW -12D 09/10/2015 6.2 3.88 57 220 <1 <1 20 <1 57 <50 <1 11.7 <10 4.1 --- 1.1 <1 <1 277 MW -12D 12/04/2015 6.1 8.08 53.2 150 c0.5 <0.5 20 <0.2 53.2 <50 0.099 11.5 <5 3.7 0.64 Ml 4.6 0.51 <1 280 MAY -1-1D 9i-/0".T2B16 6:1 9,26 53.5 678 <1 <1 22 F1 533 F50 F4 11.7 <5 4:5 B32 -h}1 2,99 <I 1-.S4 968 MW -12D 04/05/2016 5.9 9.9 55.1 370 <1 <1 21 <1 55.1 <50 <1 11.4 c5 4.5 0.6 1.64 <1 <1 385 MW -12D 07/11/2016 5.7 9.35 56.3 155 <1 <1 17 <1 56.3 <50 <1 11.5 <5 4.4 0.73 1.19 11 <1 223 Mw -1 -ZD 63 9.2 533 257 <1 <1 16 F1 53.5 -So <1 18:9 <6 4,8 - - <1 <1 4B9 MW -12D 11/04/2016 6.3 9.09 55 272 <1 <1 16 <1 55 <50 <1 10.6 BI <5 4 0.64 1.92 <1 <1 405 MW -12D 02/01/2017 6.1 8.42 54.9 115 <1 <1 14 <1 54.9 <50 <1 10.3 B2 <5 3.8 0.69 1.39 <1 <1 243 MAN --D 03/28/2017 5.9 5.7 543 340 <1 <1 45 H 54.3 <-56 <1 12-1 <5 43 0§3 3:25 <1 1.24 242 P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\Final\TABLE 1_Mayo BG GW Data_REVISED_08152017.xlsx Page 1 of 4 TABLE 1 BACKGROUND GROUNDWATER RESULTS THROUGH APRIL 2017 MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameter Lead Magnesium Manganese Mercury Methane Molybdenum Nickel Nitrate + Nitrite Potassium Selenium Sodium Strontium Sulfate Sulfide TDS Thallium TOC Vanadium Zinc Radium (Total) Uranium (Total) Reporting Units ug/L mg/L ug/L ug/L ug/L ug/L ug/L mg-N/L mg/L ug/L mg/L ug/L mg/L mg/L mg/L ug/L mg/L ug/L ug/L pCi/L ug/mL 15A NCAC 02L Standard 15 NE 50 1 NE NE 100 NE NE 20 NE NE 250 NE 500 0.2* NE 0.3* 1000 NE NE Sample ID CollecSampletionDate Analytical Results Saprolite MW -12S 09/10/2015 <1 0.723 253 <0.05 12 <1 2.98 0.7 1.53 <1 5.43 23 1.4 <0.1 55 <0.2 0.633 <0.3 64 --- --- MW-125 12/02/201 1 0:792 152 .0:05 <--10 <1 541 0.638 14 <1 5.08 24 1:3 «1 2b <0:2 0,519 0313 79 --- --- MW-12S 01/07/2016 <1 0.753 68 <0.05 <10 <1 1.6 0.599 1.58 <1 4.76 18 1.4 <0.1 35 <0.2 1.6 <0.3 157 --- --- MW-12S 04/06/2016 <1 0.749 24 <0.05 <10 <1 <1 0.798 1.22 <3 5.49 17 1.2 <0.1 29 <0.2 0.522 0.408 43 3.537 0.000367 MW -12S 07/11/2016 <1 0.694 34 <0.05 <10 <1 1.16 0.566 1.89 <3 4.34 21 1.6 <0.1 43 <0.2 2 0.974 227 2 0.00035 *w-125 04/07/2016 <1 0.64 44 .6-05 <.19 <1 .1 0.755 136 <1 4.48 16 i-4 .9.1 52 <8.2 0.763 G-.744 4 9 2.56 MW -12S 11/04/2016 <1 0.661 B1 19 <0.05 <10 <1 1.19 0.739 1.35 <3 4.85 B2 16 0.89 <0.1 52 <0.2 0.53 0.593 73 2 0.00035 MW-i2S <1 0.622 22 .&05 <14 -HS 10:3 4-:22 OA19 233 .1 4.06 14 2.3 .81 57 .0:2 3.6 0:698 64 82 1.54 0.-0002338 MW -12S 02/01/2017 2:41 - 211 <0.05 36-42 3.15 3.03 <0.01 3.78 <3 0.556-B2 25 1.6 <0.1 85 <0.2 BS 14 5:J 90 2 0.000262 Transition Zone BG -02 07/11/2011 <5 --- 64.2 <0.2 --- --- 9.4 B --- --- <10 --- --- 7.2 B --- 367 B <0.1 --- --- <10 --- --- BG-02 11/03/2011 <5 --- 36.7 <0.2 --- --- 5.2 --- --- <10 --- --- 6.9 --- 341 <0.1 --- --- <10 --- --- BG-02 04/04/2012 <5 --- 27 <0.2 --- --- <5 --- --- <10 --- --- 7.5 --- 412 <0.1 --- <10 <10 --- --- 7.7 --- 382 <0.1 --- --- <10 --- --- BG -02 11/05/2012 <5 --- 43.7 <0.2 --- --- <5 --- --- <10 --- --- 8.3 --- 389 <0.1 --- --- <10 --- --- BG-02 04/10/2013 <1 --- 111 0.18 --- --- <5 --- --- <3 --- --- 5.4 --- 430 <0.2 --- <5 BG -02 07/09/2013 <1 --- 248 0.11 --- --- <5 --- --- <3 --- --- 5.2 --- 430 <0.2 --- <5 BG -02 11/13/2013 <1 --- 177 0.11 --- --- <5 --- --- <1 --- --- 5.2 --- 360 <0.2 --- <5 BG -02 04/01/2014 <1 --- 226 0.06 --- --- <5 --- --- <1 --- --- 4.8 --- 450 <0.2 --- --- 8 BG -02 07/18/2014 <1 --- 244 0.08 --- --- <5 --- --- <3 --- --- 4.9 --- 400 <0.2 --- --- 5 BG -02 11/12/2014 <1 --- 180 <0.05 --- --- <5 --- --- <3 --- --- 5 --- 370 <0.2 --- --- 8 BG -02 04/13/2015 <1 11.8 150 0.06 --- <1 <5 --- 3.27 <3 49.7 --- 4.8 --- 380 <0.2 --- --- 11 --- --- BG-02 07/07/2015 <1 12 135 <0.05 --- <1 <5 --- 3.61 <3 48.2 --- 5.1 --- 370 <0.2 --- 5.88 15 BG -02 9/11/2015 <1 10.6 130 <0.05 400 <1 2.87 0.019 3.56 <1 44.6 291 5.4 <0.1 330 <0.2 1.4 4 23 --- --- BG-02 12/09/2015 <0.1 12.3 200 <0.2 660 0.74 0.82 <0.02 K <0.5 51.3 390 5.1 <0.1 314 <0.1 1.1 5.8 12 --- --- 86-02 ., <1 32.6 1% <G:05 473 <1 .1 .0:01 3.4 <1 503 350 S-5 -0.1 370 .41-.2 1:3 4.2 .-5 --- - BG -02 04/04/2016 <1 13.9 237 <0.05 1130 <1 <5 --- 3.34 <3 56 391 4.9 <0.1 360 <0.2 1.8 5 <5 7.07 0.00117 BG -02 07/13/2016 <1 13.5 207 <0.05 2260 <1 <5 <0.01 3.23 <3 53.3 374 4.9 <0.1 370 <0.2 1.6 4.79 <5 7.52 0.001068 BG -02 0 <-1 131 11)4 <0:05 1670 <1 <1 <0:01 3.31 .4 53.3 378 53 <0.1 370 .42 4-6 5.34 .5 1-.947 0900941 BG -02 11/02/2016 <1 10.8 131 <0.05 1120 N2 <1 <1 0.02 3.48 <1 45.3 320 5.6 <0.1 330 H1 <0.2 1.4 3.63 <5 3.36 0.001005 BG -02 01/30/2017 <1 10.6 104 <0.05 801 N2 <1 <1 <0.01 3.48 <1 44 B2 287 5.6 <0.1 320 <0.2 1.4 4.14 B2 <5 2 0.001076 MW -12D 06/24/2015 <1 3.44 683 <0.05 <10 1,75 2.5 0.08 1.6 <3 8.98 95 0.96 <0.1 120 <0.2 0.396 0.719 <5 --- --- MW-12D 09/10/2015 <1 3.04 218 <0.05 <10 <1 1.35 0.654 1.41 <1 9.03 85 0.99 <0.1 100 <0.2 1.7 0.637 9 --- --- MW-12D 12/04/2015 <0.1 3.24 160 <0.2 <10 0.8 3.7 0.15 <5 <0.5 9.56 85 <1 <0.1 122 <0.1 <1 <1 <10 --- --- MW-12D <1 3.28 1-31 <-0-.85 .19 <1 2:23 07439 1-39 .1 8:76 87 1-1.a.1 82 .8.2 0.184 135 5 --- --- MW-12D 04/05/2016 <1 3.27 100 <0.05 <10 <1 1.49 0.146 1.42 <3 9.35 92 1.1 <0.1 120 <0.2 0.314 1.06 <5 9 0.000383 MW -12D 07/11/2016 <1 3.16 81 <0.05 17.9 <1 1.23 0.176 1.36 <3 9.26 88 1.1 <0.1 98 <0.2 0.276 0.898 6 3.62 0.0002419 MW -12D 0 <1 302 64 .005 19:4 <1 2:02 038 1.34 .4 9,85 83 1.4 1-0:1 100 .42 0,289 143 5 3.19 0.000» MW -12D 11/04/2016 <1 2.97 B1 56 <0.05 28.5 N2 <1 1.37 0.166 1.37 <3 8.39 B2 85 1.1 <0.1 110 <0.2 0.171 1.25 <5 1.659 0.000318 MW -12D 02/01/2017 <1 2.8 96 <0.05 71 N2 <1 1.62 0.19 1.22 <3 8.16 B2 83 1 <0.1 110 <0.2 B5 0.366 0.874 <5 1.835 0.000296 MW -121D 0 <1 3.2 45 .005 .19 <-1 1-29 0:i9 1,44 <1 9,26 &5 1.1 <GA % 0-.-2 0:192 83 0.805 <3 P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\Final\TABLE 1_Mayo BG GW Data_REVISED_08152017.xlsx Page 2 of 4 TABLE 1 BACKGROUND GROUNDWATER RESULTS THROUGH APRIL 2017 MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameter PH Turbidity Alkalinity Aluminum Antimony Arsenic Barium Beryllium Bicarbonate Boron Cadmium Calcium Carbonate Chloride Chromium (VI) Chromium Cobalt Capper Iron Reporting Units S.U. NTUS mg/L ug/L ug/L ug/L ug/L ug/L mg/L ug/L ug/L mg/L mg/L mg/L ug/L ug/L ug/L ug/L ug/L 15A NCAC 02L Standard 6.5-6.5 NE NE NE 1* 10 700 4* NE 700 2 NE NE 250 SO SO 1* 1000 300 Sample ID Sample Collection Date Field Parameters Analytical Results Bedrock BG -01 11/3/2011 5.5 3.84 - 216 <0.5 .-5 95.4 - - <50 0.2 - - 13.1 - 7.9 - <5 261 BG -01 04/04/2012 5.6 9.52 - 191 .0.5 <-5 93 - - <50 0.12 - - 14.3 - 6.7 - <S 388 BG -01 07/09/2012 5.3 9.32 - 478 <0.5 <5 101 - - <50 0.13 - - 14.6 - 20 ju - <5 640 BG -01 11/05/2012 5.4 9.45 - 465 <0.5 15 101 - - <50 0.089 - - 13.4 - <5 - <S 526 BG -01 04/10/2013 5.2 9.05 - 202 <1 <1 97 - - <50 <1 - - 13 - 7 - <5 323 BG -01 07/09/2013 5.4 8.95 - 383 <1 <1 97 - - <50 <1 - - 13 - <5 - <5 488 BG -01 11/13/2013 5.5 8.2 - 339 <1 <1 95 - - <50 <1 - - 12 - <5 - <5 412 BG -01 04/01/2014 5.4 8.2 - 202 <1 <1 90 - - <50 <1 - - 12 - <5 - <5 290 BG -01 07/18/2014 5.5 6.68 - 245 <1 <1 93 - - <50 <1 - - 12 - <5 - <5 325 BG -01 11/12/2014 5.5 9.96 - 332 <1 <1 95 - - <50 <1 - - 12 - <5 - <5 466 BG -01 04/13/2015 5.5 8.9 49.8 392 <1 <1 90 <1 49.8 <50 <1 12.5 <5 11 - <5 <1 <5 409 BG -01 09/10/2015 5.3 7.83 54 276 <1 <1 91 <1 54 <50 <1 12.8 <10 11 - <1 <1 <1 300 BG -01 6:1 4-49 52-:1 33 <4 H 90 <4 52-:1 <So <4 -12.8-82 <-5 472 K F1 K 45 BG -01 12/05/2015 5.5 9.5 52.8 250 <0.5 <0.5 94 <0.2 52.8 <50 0.13 12.6 <5 10.1 0.31 1 <0.5 <1 350 6G-01 5-.17 548 54-.4 227 <4 �4 87 <4 54-.1 -50 <4 42-6 K 472 01.4 F-1 <4 F4 272 BG -01 04/04/2016 5.5 4.3 53 177 <1 <1 88 <1 53 <50 <1 12.1 <5 11 0.19 MS <5 <1 <5 190 BG -01 07/13/2016 5.0 3.84 53.1 66 <1 <1 86 <1 53.1 <50 <1 12.3 <5 12 0.23 <5 <1 <5 89 86-01 5.5 449 529 275 <4 <1 90 -.4 52.9 -50 <1 472 K 11 03 <1 <4 <1 336 BG -01 11/02/2016 5.5 2.98 52.8 48 <1 <1 90 <1 52.8 <50 <1 12.4 <5 11 0.23 <1 <1 <1 50 BG -01 02/04,12017 3-6 4-.37 §2 8 231 <4 E4 87 F4 528 F50 F4 42-2 <-5 45 0:29 F4 F4 4..2 200 BG -01 03/28/2017 5.4 0.47 53 218 <1 <1 87 <1 53 <50 <1 12.9 <5 11 0.25 <1 <1 <1 137 MW-13BR 06/23/2015 7.2 2.22 210 37 <1 <1 40 <1 210 <50 <1 75.2 <10 46 - <1 1.19 <1 1130 MW-13BR 09/08/2015 6.9 7.55 230 143 B1 <1 <1 51 <1 230 <50 <1 73 <10 43 - <1 <1 <1 2400 MVI-13BR 12/02,12015 36 63 210 474 <1 <1 45 .4 210 <50 <4 727 <10 41 .0:03 4§3 <1 4-:2 2490 MW-13BR 01/07/2016 7.3 7.79 223 M1 230 <1 <1 42 <1 223 <50 <1 73.3 <5 45 <0.03 7.65 <1 <1 2550 MW-13BR 04/05/2016 7.1 9.05 217 97 <1 <1 35 <1 217 <50 <1 70.8 <5 43 <0.03 <1 1.01 <1 1750 MW-13BR 07/11/2016 7.0 8.8 211 407 <1 <1 29 <1 211 <50 <1 70.2 <5 40 <0.03 4.51 1.92 1.95 1330 MVI-13SR 09/06,1201 7,4 9,611 246 434 <4 <1 38 <4 216 <50 <4 69-.7 <3 38 <4-G3 262 1:17 .1 2520 MW-13BR 11/08/2016 6.9 9.9 221 102 <1 <1 35 <1 221 <50 <1 67 <5 37 0.18 3.58 2$9 <1 2430 MW-13BR 02/02/2017 6.9 9.13 213 91 <1 <1 31 <1 213 <50 <1 65 <5 34 0.26 2.7 2-.-91 <1 2920 MW-14BR 03/12/2015 6.7 35 96 589 <1 <1 30 <1 96 <50 <1 19.5 <10 9.3 - <1 1.41 4.5 907 MW-14BR 09/09/2015 6.9 3.36 160 61 <1 1.8 42 <1 160 65 <1 20.2 <10 11 - <1 1.09 <1 2730 MW -1488 6-.7 2.77 400 77 <4 <1 22 <1 100 <50 <1 434 <40 14 <0-03 <1 <4 <1 3% MW-14BR 01/07/2016 6.7 2.45 94.8 163 <1 <1 17 <1 94.8 <50 <1 13 <5 13 <0.03 <1 <1 1.21 98 MW-14BR 04/05/2016 6.7 2.45 104 225 <1 <1 19 <1 104 <50 <1 13 <5 13 <0.03 <1 <1 1.87 89 MW-14BR 07/11/2016 6.7 1.34 130 58 <1 <1 22 <1 130 <50 <1 14.4 <5 13 <0.03 <1 <1 1.58 37 ,w-IiBR 6.4 5769 130 59 <4 H 28 <4 130 <50 <4 IS -3-M4 K 14 .0.03 <4 <1 443 56 MW -1411R 11/08/2016 7.0 3.74 136 129 <1 <1 28 <1 136 <50 <1 16.2 <5 13 .0.025 <1 1.14 1.97 172 MW-14BR 02/02/2017 6.7 1.14 121 63 <1 <1 19 <1 121 <50 <1 28.9 <5 13 0.067 <1 <1 1.36 31 Prepared by: JHG Checked by: JAW Notes: 34 - Indicates value omitted from dataset. Indicates parameter not measured analyzed. - Indicates data removed /identified ass an outlier. - Indicates data removed due to autocorrelation. mg - N/L - Milligrams nitrogen per liter pCi/L - picocuries per liter mg/L - Milligrams per liter S.U. - Standard Unit NE - Not established ug/L - Micrograms per liter NTU - Nephelometric turbidity unit ug/mL - micrograms per milliliter < - concentration not detected at or above the reporting limit. * - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April, 1, 2013. BS - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample was greater than SOX the concentration: in the method blank. Analyte concentration in sample is not affected by blank contamination. B2 - Target analyte was detected in blank(s) at a concentration greater than 1/2 the reporting limit but less than the reporting limit. Analyte concentration in sample is valid and may be used for compliance purposes. BS - Target analyte was present in blank(s) above the method detection limit but less than the reporting limit. Data is valid for compliance purposes. HS - Results are from sample aliquot taken from VOA vial with headspace (air bubble greater than 6 mm diameter). P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\Final\TABLE 1_Mayo BG GW Data_REVISED_08152017.xlsx Page 3 of 4 TABLE 1 BACKGROUND GROUNDWATER RESULTS THROUGH APRIL 2017 MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Analytical Parameter Lead Magnesium Manganese Mercury Methane Molybdenum Nickel Nitrate + Nitrite Potassium Selenium Sodium Strontium Sulfate Sulfide TDS Thallium TOC Vanadium Zinc Radium (Total) Uranium (Total) Reporting Units ug/L mg/L ug/L ug/L ug/L ug/L ug/L mg -NIL mg/L ug/L mg/L ug/L mg/L mg/L mg/L ug/L mg/L ug/L ug/L pCi/L ug/mL SSA NCAC 02L Standard 15 NE 50 1 NE NE 100 NE NE 20 NE NE 250 NE 500 0.2* NE 0.3* 1000 NE NE Sample ID Sample Collection Date Analytical Results Bedrock BG -01 11/03/2011 <5 - 8.9 «.2 - - 6.2 - - <1-0 - - <5 - 106 <0.1 - - <10 - - BG -01 04/04/2012 <-5 - 11.6 60-.2 - - <5 - - <30 - - <5 - 107 <0.1 - - <10 - - BG -01 07/09/2012 <5 - 21.6 --0-.2 - - 9.4 - - HO - - 2 - 128 <0.1 - - <10 - - BG -01 11/05/2012 <5 - .55.6 «.2 - - <5 - - <30 - - <2 - 123 <0.1 - - 11.6 - - BG -01 04/10/2013 <1 - 15 <0.05 - - <5 - - <1 - - 0.44 - 130 <0.2 - - 7 - - BG -01 07/09/2013 <1 - 48 <0.05 - - <5 - - <1 - - 0.52 - 130 <0.2 - - 12 - - BG -01 11/13/2013 <1 - 27 <0.05 - - <5 - - <1 - - 0.51 - 130 <0.2 - - 30 - - BG -01 04/01/2014 <1 - 14 <0.05 - - <5 - - <1 - - 0.4 - 140 <0.2 - - 29 - - BG -01 07/18/2014 <1 - 15 <0.05 - - <5 - - <1 - - 0.46 - 140 <0.2 - - 16 - - BG -01 11/12/2014 <1 - 25 <0.05 - - <5 - - <1 - - 0.51 - 120 <0.2 - - 34 - - BG -01 04/13/2015 <1 3.35 35 <0.05 - <1 <5 - 1.4 <1 12.4 - 0.32 - 130 <0.2 - - 29 - - BG -01 09/10/2015 <1 3.41 26 <0.05 4-6 <1 1.78 0.645 1.38 <1 11.6 172 0.37 <0.1 120 <0.2 0.913 3.93 17 - - BG -01 <3 328 7 -4-0`5 --- F1 <5 +.35 <4 44-8-132 179 036 - 14-0 <$.2 34 65 - BG -01 12/05/2015 0.13 3.28 18 6&2 <10 <0.5 1.9 0.66 <5 <0.5 12.2 180 <1 <0.1 118 <0.1 1 4.2 14 - - BG -04 -1 336 14 <665 F-19 <3 1.24 8-643 1.39 <3 119 166 0.24 <-�)4 130 <-0-.2 0:558 394 K BG -01 04/04/2016 <1 3.2 12 <0.05 <10 <1 <5 - 1.36 <1 11.5 167 0.25 <0.1 130 <0.2 0.738 3.94 7 5.25 0.00035 BG -01 07/13/2016 <1 3.09 7 <0.05 <10 <1 <5 0.827 1.28 <3 11.9 177 0.23 <0.1 140 <0.2 0.723 3.58 <5 2.29 0.00035 BG -04 <3 324 13 -c 0 <" <3 4-46 0-828 4.32 14 34-4 172 032 <-8-1 130 <-0-.2 8667 469 26 3876 0330035 BG -01 11/02/2016 <1 3.18 8 <0.05 <10 N2 <1 1.82 0.811 1.31 <1 11.4 183 0.26 <0.1 110 Hl <0.2 0.565 3.82 <5 6.24 0.00035 BG -01 02101,1201E-1 319 43 60.65 H6-142 <4 4:6 0-809 1.33 F3 13-2 174 0-26 140 0.783 F5 2 0-:06635 BG -01 03/28/2017 <1 3.28 10 <0.05 <10 <1 1.41 0.834 1.38 <1 12.5 173 0.25 <0.1 120 <0.2 0.64 B3 4 <5 2.862 0.00035 MW-13BR 06/23/2015 <1 13.1 474 <0.05 <10 8.28 <1 <0.01 5.49 <1 25.7 418 18 0-115 370 <0.2 0.9 0.381 36 4.22 0.00035 MW-13BR 09/08/2015 <1 12.9 630 <0.05 <10 5.17 <1 <0.01 M2 5.31 <1 24.8 430 12 <0.1 360 0§38 0.859 0.465 99 - - 12102/201 <3 133 548 60 -,OS <38 5$67: Y7 <8.81 5-.09 <1 233 416 14 .2 330 <6.2 0,761 0429 54 MW-13BR 01/07/2016 <1 12.9 519 <0.05 289 5.81 4.98 <0.01 5.12 <1 23.7 389 15 <0.1 330 <0.2 0.647 <0.3 37 - - MW-13BR 04/05/2016 <1 12.9 481 <0.05 27 4.3 <1 <0.01 4.72 <1 20.8 393 17 <0.1 340 <0.2 0.733 <0.3 9 5.65 &.60644 MW-13BR 07/11/2016 <1 13 348 <0.05 5" 3.2 2.82 <0.01 4.72 <1 19.4 380 18 <0.1 330 <0.2 0.594 0.871 23 3.103 0.00203 MMI-13SR 09/06,12016<3 12.7 432 <-0-OS 135 2.98 168 60.01 438 <1 18.4 381 16 <0-1 330 E0.-2332 G-.64,5 «3 38 6" 03300681 MW-13BR 11/08/2016 <1 12.3 471 <0.05 993#2 2.85 2.26 <0.01 4.46 <3 17.3 374 15 <0.1 310 <0.2 0.574 0.38 6 1.392 0.000569 MW-13BR 02/02/2017 <1 12 421 <0.05 55#2 2.35 1.39 <0.01 4.43 <3 16.8 353 15 <0.1 320 <0.2 0.458 0.406 <5 2.01 0.000617 MW-14BR 03/12/2015 <1 2.96 544 <0.05 <10 14 <1 0.039 4.08 <1 33 149 12 <3 190 <0.2 1.3 1.29 10 - - MW-14BR 09/09/2015 <1 3.07 648 <0.05 13 27-.3 <1 0.011 M2 6.56 <1 60.2 167 27 <0.1 260 <0.2 1.3 0.469 <5 - - ...�-.o.� <3 2-.29 304 60.05 <38 662 61 0-112 5-.75 <3 416 144 10 <0-1 216 8.822 1$2 K MW-14BR 01/07/2016 <1 2.36 199 <0.05 <10 4.56 <1 0.384 4.49 <1 37.4 131 10 <0.1 180 <0.2 0.855 2.45 <5 - - MW-14BR 04/05/2016 <1 2.36 196 <0.05 <10 5.06 <1 0.346 4.06 <1 38.4 134 9.9 <0.1 200 <0.2 0.873 2.86 <5 3.999 0.000391 MW-14BR 07/11/2016 <1 2.51 247 <0.05 <10 8.07 <1 0.157 5.18 <1 47.9 140 11 <0.1 200 <0.2 0.84 2.48 11 1.947 0.000606 ,a1 <3 2.37 322 <0-.05 <.10 937 H 0-191 7.13 <1 46.3-M4 168 12 <0.1 <6-.2 0.887 2.67 7 3 0669464 MW-14BR 11/08/2016 <1 2.64 385 <0.05 12.2-N2 10.7 <1 0.187 6.78 <3 49.9 158 9.6 <0.1 �220 <0.2 0.785 1.56 6 2.07 0.000539 MW-14BR 02/02/2017 <1 13.1 96 <0.05 110 N2 5.04 <1 0.291 4.04 <1 38.4 150 8.6 <0.1 <0.2 0.832 2.07 <5 2 0.000355 Prepared by: JHG Checked by: JAW Notes: 54 - Indicates value omitted from dataset. - Indicates parameter not measured or analyzed. ®Indicates data removed /identified as an outlier. - Indicates data removed due to autocorrelation. mg - N/L - Milligrams nitrogen per liter pCi/L - picocuries per liter mg/L - Milligrams per liter S.U. - Standard Unit NE - Not established ug/L - Micrograms per liter NTU - Nephelometric turbidity unit ug/mL - micrograms per milliliter < - concentration not detected at or above the reporting limit. * - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April, 1, 2013. Bl - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample was greater than IOX the concentration in the method blank. Analyte concentration in sample is not affected by blank contamination. B2 - Target analyte was detected in blank(s) at a concentration greater than 1/2 the reporting limit but less than the reporting limit. Analyte concentration in sample is valid and may be used for compliance purposes. B5 - Target analyte was present in blank(s) above the method detection limit but less than the reporting limit. Data Is valid for compliance purposes. HS - Results are from sample aliquot taken from VOA vial with headspace (air bubble greater than 6 mm diameter). P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\Final\TABLE 1_Mayo BG GW Data_REVISED_08152017.xlsx Page 4 of 4 TABLE 2 GROUNDWATER BACKGROUND THRESHOLD VALUES MAYO STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ROXBORO, NC Parameter Reporting Unit NCAC 02L Standard Surficialt Background Threshold Values Transition Zone Bedrock pH* S.U. 6.5-8.5 4.9 -6.5 5.7 -6.5 5.0 - 7.3 Alkalinity mg/L NE 13 302 223 Aluminum Ng/L NE 566 490 536 Antimony pg/L 1° 1 1 1 Arsenic pg/L 10 1 1 1 Barium pg/L 700 19 78.3 97 Beryllium pg/L 4° 1 1 1 Bicarbonate mg/L NE 13 302 223 Boron pg/L 700 50 50 50 Cadmium pg/L 2 1 1 1 Calcium mg/L NE 2.89 59.2 73.3 Carbonate mg/L NE 5 5 5 Chloride mg/L 250 3.3 33.3 43 Chromium (VI) pg/L 10 0.088 1.26 0.4 Chromium pg/L 10 3.23 6 7 Cobalt pg/L 1° 1.02 1 1.19 Copper Ng/L 1000 1.9 5 5 Iron Ng/L 300 385 1319 2550 Lead Ng/L 15 1 1 1 Magnesium mg/L NE 0.753 13.5 13.1 Manganese pg/L 50 253 298 544 Mercury pg/L 1 0.2 0.2 0.05 Methane pg/L NE 12 2256 10 Molybdenum pg/L NE 3.15 1 13.1 Nickel pg/L 100 3.03 5 5 Nitrate + Nitrite mg-N/L NE 0.798 0.295 1.03 Potassium mg/L NE 3.78 3.61 6.56 Selenium pg/L 20 1 1 1 Sodium mg/L NE 5.49 53.3 72.6 Strontium pg/L NE 25 391 418 Sulfate mg/L 250 1.6 7.5 18 Sulfide mg/L NE 0.1 0.1 0.1 TDS mg/L 500 85 430 340 Thallium pg/L 0.2° 0.2 0.2 0.2 TOC mg/L NE 2 1.8 1.01 Vanadium pg/L 0.3° 0.974 5.88 5.52 Zinc pg/L 1000 227 12 37.9 Radium (Total) pCi/L NE 4 9t 7.6 Uranium (Total) pg/mL NE 0.000367 0.001t 0.00203 Prepared by: JHG Checked by: JAW / RKD Notes: * - Upper and lower tolerance limits calculated for parameter A - Interim Maximum Allowable Concentrations (IMACs) of 15A NCAC .02L Standard, Appendix 1, April 1, 2013 pg/L - micrograms per liter pg/mL - micrograms per milliliter t - Indicates value is provisional; dataset contains less than 10 valid samples Bedrock background wells: BG -1, MW-13BR, and MW-14BR mg/L - milligrams per liter ND - Not Detected NE - Not Established pCi/L - picocuries per liter Radium (Total) - Radium -226 and Radium -228 combined S.U. - Standard Unit Surflcial (Saprolite) background wells: MW -12S TDS - Total Dissolved Solids Transition Zone background wells: BG -2 and MW -12D Uranium (Total) - Uranium -233, Uranium -234, Uranium -236, and Uranium -238 combined P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\Final\TABLE 2 - Mayo GW BGTVs REVISED 08152017.xlsx Page 1 of 1