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Home My WebLink AboutWspoon - GW BTV MEMO_FINAL_20170905TECHNICAL MEMORANDUM Date: September 5, 2017 File: 1026.09 To: Bryson Sheetz and Ryan Czop (Duke Energy) Cc: Kathy Webb (SynTerra) From: Ted Volskay (SynTerra) Subject: Background Threshold Values for Groundwater W.H. Weatherspoon Power Plant— Lumberton, NC 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) and the background groundwater dataset for the W.H. Weatherspoon Plant (Weatherspoon) were submitted to North Carolina Department of Environmental Quality (NCDEQ) on May 26, 2017. NCDEQ subsequently 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). As outlined in the NCDEQ July 7, 2017 letter, Duke Energy is required to provide BTVs for both media within 60 days from receipt of the NCDEQ letter for facilities submitting Comprehensive Site Assessments (CSAs) later than October 31, 2017. BTVs for soil are provided under separate cover. The 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 be computed to be either: h The highest value, or y 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: 01 Sample pH is greater than 8.5 standard units (S.U.) unless the regional DEQ office has determined an alternate background threshold pH for the site; P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH MEMO\ Weatherspoon \Groundwater\Wspoon- GW BTV MEMO_FINAL.docx Background Threshold Values for Groundwater September 5, 2017 W.H. Weatherspoon Power Plant Page 2 of 3 h Sample turbidity is greater than 10 Nephelometric Turbidity Units (NTUs); y Result is a statistical outlier identified for background sample data presented to NCDEQ on May 26, 2017; y Sample collection occurred less than a minimum 60 days between sampling events; and y Non -detect results are greater than 2L/IMAC. Additional site -specific requirements related to groundwater background dataset for Weatherspoon, such as exclusion of data not approved by NCDEQ (NCDEQ July 7, 2017), 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, lower Yorktown, and Pee Dee. Background 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. 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 results of statistical evaluations for determining BTVs. SURFICIAL Four wells, BW-02S, BW-03S, CCR-101-BG, and MW-01, are used to monitor background groundwater quality within the surficial flow zone. In the July 7, 2017 letter, NCDEQ concurred with the background locations and samples proposed for the surficial flow zone background dataset. Background groundwater samples collected less than 60 days between sampling events, statistical outliers, and invalid data were omitted prior to statistical determinations. The resulting surficial background dataset meets the minimum requirement of 10 samples for all constituents. The surficial background dataset is presented in Table 1. BTVs were calculated for constituents monitored within the surficial flow system using formal UTL statistics. BTVs for the surficial flow system are provided in Table 2. LOWER YORKTOWN One well, BW-03I, monitors background groundwater quality within the lower Yorktown. In the July 7, 2017 letter, NCDEQ concurred with this background location and samples proposed for the lower Yorktown background dataset. Background groundwater samples collected less than 60 days between sampling events, statistical outliers, and invalid data were omitted prior P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH MEMO\ Weatherspoon \Groundwater\Wspoon- GW BTV MEMO_FINAL.docx Background Threshold Values for Groundwater September 5, 2017 W.H. Weatherspoon Power Plant Page 3 of 3 to statistical determinations. The resulting background dataset does not meet the minimum requirement of 10 samples for all constituents. Table 1 presents the background dataset for the lower Yorktown. No formal UTL statistics were performed because Yorktown background dataset does not meet the minimum requirement of 10 samples for all constituents. Therefore, the PBTVs for Yorktown constituents were computed to be the highest value, provided that the highest value was not above an order of magnitude greater than the geometric mean of all values. If the highest value was an order of magnitude greater than the geometric mean of all values, the PBTV was computed to be the second highest value. PBTVs for the lower Yorktown flow zone are presented in Table 2. PEE DEE One well, BW-03D, monitors background groundwater quality within the Pee Dee. In the July 7, 2017 letter, NCDEQ concurred with the background location and samples proposed for the Pee Dee background dataset. Background groundwater samples collected less than 60 days between sampling events, statistical outliers, and invalid data were omitted prior to statistical determinations. The resulting Pee Dee background dataset does not meet the minimum requirement of 10 samples for all constituents. Table 1 presents the background dataset for the Pee Dee. No formal UTL statistics were performed because Pee Dee background dataset does not meet the minimum requirement of 10 samples for all constituents. Therefore, PBTVs for thePee Dee constituents were computed to be the highest value, provided that the highest value was not above an order of magnitude greater than the geometric mean of all values. If the highest value was an order of magnitude greater than the geometric mean of all values, the PBTV was computed to be the second highest value. PBTVs for the Pee Dee are presented in Table 2. LIST OF FIGURES: Figure 1 Approved Background Groundwater Monitoring Well Location Map LIST OF TABLES: Table 1 Updated Background Groundwater Analytical Results through March 2017 Table 2 Background Groundwater Threshold Values P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH MEMO\Weatherspoon\Groundwater\Wspoon- GW BTV MEMO_FINAL.docx Background Threshold Values for Groundwater September 5, 2017 W.H. Weatherspoon Power Plant FIGURE P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 72017\BTV TECH MEMO \ Weatherspoon \ Groundwater \ Wspoon - GW BTV MEMO_FINAL.docx a (I M Y �k a r a �t �t � lA It Tf, ®�— r '� r '., tx V A, 40 '�'��T - �" ��,f�. '��'{fir}•' ,pr` NOTES:'„ 2014 AERIAL ORTHOPHOTOGRAPHY OBTAINED FROM USDA NRCS GEOSPATIAL DATA GATEWAY A (https://gdg.sc.egov.usda.gov/GDGOrder.aspx). K'` f DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH ' �✓ = j j CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 , (NAD83/2011). .I W , MW-33S MW-33D � MW-331 C k a� W-1S W�1 D T, 7 dS- •J1r` � y•' ; � r 1) Ilk IL Vuhud -'u 71 r , MW 44S \ MW-44 MW-44: MW-44., •rah wi +1l�yFyy, ♦ i[ 1w� Id • S CW_2 El uYN v . OB-1 MW-52 OB-2 r -, MW~4 ..... 1 't . MW-54D •1*, s' MW-6 MW;'� MW-7 MW-% �= LEGEND APPROVED BACKGROUND C 0 GROUNDWATER MONITORING ". WELL LOCATION (7/7/17) MW;53D MONITORING WELL LOCATION MW-531 CW-1 �! ■ PIEZOMETER LOCATION ABANDONED MONITORING WELL LOCATION a ABANDONED PIEZOMETER LOCATION CCR SURFACE IMPOUNDMENT BOUNDARY DUKE ENERGY PROGRESS WEATHERSPOON PLANT SITE BOUNDARY 250 125 0 250 500 GRAPHIC SCALE IN FEET FIGURE 1 APPROVED BACKGROUND GROUNDWATER 148 RIVER STREET, SUITE 220 GREENVILLE, SOUTH CAROLINA 29601 MONITORING WELL SAMPLING LOCATION MAP PHONEs6r ";Or-9999 W.H. WEATHERSPOON POWER PLANT synTerra WWWs nteANAGE cT. DRAWN III A. FEIGL DATE:09/01/2017 LUMBERTON, NORTH CAROLINA PROJECT MANAGER: T. VO LSKAY CHECKED BY: T.VOLSKAY P:\Duke Ener Pro ress.1026\00 GIS BASE DATA\Weathers oon\Ma Docs\Back round\Weathers oon BKGDGW 2017081.mxd Background Threshold Values for Groundwater September 5, 2017 W.H. Weatherspoon Power Plant TABLES P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 72017\BTV TECH MEMO \ Weatherspoon \ Groundwater \ Wspoon - GW BTV MEMO_FINAL.docx TABLE 1 UPDATED BACKGROUND GROUNDWATER ANALYTICAL RESULTS THROUGH MARCH 2O17 W.H. WEATHERSPOON POWER PLANT DUKE ENERGY PROGRESS, LLC, LUMBERTON, NC ��®�e�®mmme�m�vaa®mm�®�®� emme�m�maa�va�®m® 'Lower Yorktown Notes: S4 -Indicates value omittetl from tlataset. - Indicates parameter n0[ measuretl or analyzetl. Indicates tla[a removetl /identifetl as an outlier - Intllcates tlata removetl tlue to auroc0rrelatipn < - cpncen[rati0n not detected at or above the atljustetl reporting limit. NTU - Nephelometric turbidityunit 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 : - Interim Maximum Allowable Concentrations (IMAC,) of the 15A NCAC 02L Standard, Appendix 1, April, 1, 2013. - Hexavalen[ chromium tloes no[ have a NC 2U1MAC standard; therefore, [he NC 2L stantlartl for total chromium is relietl upon as a surrogate. 82 - Target onslyte was detected in blanks) st 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. D3 - Sample was diluted tlue W the presence of high levels of non -target analytes or Other matrix intenerence. j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit. 42 - Matrix spike recovery was Low: the...ciated Laboratory Control Spike (LCS) was acceptable. N2 - The lab tloes not hold accreditation for this parameter. 5 - Asspciatetl calib b— check did not meet specified criteria. Prepared bv: ILK Checked by: V P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BN TECH MEMO\Weatherspoon\Groundwater\Table 1 - BG GW Data 032017 Page 1 of 1 TABLE 2 BACKGROUND GROUNDWATER THRESHOLD VALUES W.H. WEATHERSPOON POWER PLANT DUKE ENERGY PROGRESS, LLC, LUMBERTON, NC Parameter Reporting Unit NCAC 02L Standard Background Threshold Values Surficial Lower Yorktown Pee Deet pH* S.U. 6.5-8.5 3.21 - 6.87 5.5 - 5.7 6.9 - 8.3 Alkalinity mg/L NE 36.5 17.4 89 Aluminum Ng/L NE 1460 492 66 Antimony Ng/L 1A ND 1 1 Arsenic Ng/L 10 1.35 1 1 Barium pg/L 700 31.9 21 56 Beryllium pg/L 4A ND 1 1 Bicarbonate mg/L NE 36.5 17.4 89 Boron Ng/L 700 ND 50 50 Cadmium Ng/L 2 ND 1 1 Calcium mg/L NE 14.5 7.02 30 Carbonate mg/L NE ND 5.00 10 Chloride mg/L 250 22.2 10 3.4 Chromium (VI) 1 pg/L 10 0.047 0.84 0.2 Chromium Ng/L 10 1.63 1.34 1 Cobalt pg/L 1A ND 1 1 Copper Ng/L 1000 ND 1 1 Iron pg/L 300 13231 2070 1550 Lead Ng/L 15 ND 1 1 Magnesium mg/L NE 1.39 0.487 1.11 Manganese pg/L 50 39 20 41 Mercury ug/L 1 ND 0.05 0.05 Methane Ng/L NE 442 1080 238 Molybdenum pg/L NE ND 1 1 Nickel ug/L 100 ND 1 1 Nitrate + Nitrite mg-N/L NE 2.09 0.01 0.01 Potassium mg/L NE 1.16 0.885 1.62 Selenium Ng/L 20 ND 1 1 Sodium mg/L NE 13 6 7.32 Strontium Ng/L NE 88 41 164 Sulfate mg/L 250 13.7 1.3 0.24 Sulfide mg/L NE 0.29 0.1 0.1 TDS mg/L 500 90.3 75 130 Thallium pg/L 0.2A ND 0.2 0.2 TOC mg/L NE 7.9 3.5 1.1 Vanadium Ng/L 0.3A 4.65 2.61 0.3 Zinc pg/L 1000 10 5 5 Radium (Total) pCi/L NE 7.09 5.4 3.55 Uranium (Total) Ng/mL NE 0.0006 0.001 0.0004 Prepared by: LWD Checked by: THE N.tes; * - 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 - Provisional; dataset contains less than 10 valid samples ' - Hexavalent chromium does not have a NC 2L/IMAC standard; therefore, the NC 2L standard for total chromium is relied upon as a surrogate. mg - N/L - Milligrams nitrogen per liter mg/L - milligrams per liter NE - Not Established ND - Not Detected pCi/L - picocuries per liter Radium (Total) - Radium-226 and Radium-228 combined S.U. - Standard Unit TDS - Total Dissolved Solids TOC - Total Organic Carbon Uranium (Total) - Uranium-233, Uranium-234, Uranium-236, and Uranium-238 combined P:\Duke Energy Pmgmss.1026\Statisti6_CAMA\Background Determinations for NCDEQ July 7 2017\13TV TECH MEMO\Weatherspoon\Groundwater\Table\Table 2 - WSPN GW BG Threshold Values Page 1 of I