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Home My WebLink AboutCape Fear- SOIL BTV MEMO_FINALTECHNICAL MEMORANDUM Date: September 5, 2017 File: 1026.103 To: Ryan Czop (Duke Energy) Cc Kathy Webb (SynTerra) From: Chris Suttell (SynTerra) Subject: Background Threshold Values for Soil Cape Fear Steam Electric Plant Station — Moncure, NC An updated background soil dataset was provided to the North Carolina Department of Environmental Quality (NCDEQ) for Cape Fear Steam Electric Plant (Cape Fear) 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 60 days from receipt of the NCDEQ letter for facilities submitting Comprehensive Site Assessments (CSAs) later than October 31, 2017. BTVs for groundwater are provided under separate cover. Updated background soil datasets provided to NCDEQ on May 26, 2017 incorporated comments provided in a letter by NCDEQ (Zimmerman to Draovitch, April 28, 2017). NCDEQ requested that Duke Energy collect a minimum of 10, rather than the previously planned eight, valid background samples prior to the determination of BTVs for each constituent. For soil datasets with less than 10 valid samples available for BTV determination, no formal upper tolerance limit (UTL) statistics could be run and the provisional BTV (PBTVs) for a constituent was computed to be either: 01 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. Soil samples meeting the following criteria are considered valid for use in statistical determinations of BTVs: 01 Sample was collected from a location that is not impacted by coal combustion residuals or coal associated materials; P: \ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination Reports \ Soil \ Cape Fear- SOIL BTV MEMO_FINAL.docx Background Threshold Values- Soil September 5, 2017 Cape Fear Steam Electric Plant Page 2 of 3 01 Sample was collected from a depth not less than 0.5 feet below ground surface; h Sample was collected from a location that is not impacted by other potential anthropogenic sources of constituents; and y Sample is collected from the unsaturated zone, greater than one foot (ft) above the seasonal high water table elevation. Additional site-specific requirements related to the Cape Fear background soil dataset as outlined in the July 7, 2017 NCDEQ letter have been incorporated into the soil background dataset. This technical memorandum summarizes the revised background soil 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). SOIL BACKGROUND DATA Soil samples were collected from soil borings conducted at Cape Fear during the 2015 Comprehensive Site Assessment (CSA). Additionally, soil samples collected in 2013 by Geosyntec as part of a voluntary assessment are included in the background dataset. Background soil sample locations are presented in Figure 1. The background dataset provided to NCDEQ on May 26, 2017 included pooled soil samples collected from multiple depth intervals. Only samples collected from background locations at depth intervals greater than one foot above the seasonal high water table were included in the dataset. The background soil dataset has been further revised from the May 26, 2017 submittal based on input from NCDEQ in the July 7, 2017 letter. NCDEQ determined the following samples are not appropriate for use in determining BTVs: h MW-05BR SB (0-2), MW -09 SB (0-2), MW-10BR SB (0-2), MW-12BR SB (0-2), MW -15 SB (0-2), MW -20 SB (0-2), MW -22 SB (0-2), and MW -23 SB (0-2) — collected too shallow; ,Ci BG -04 (Geosyntec) (2.0-2.5) and BG -05 (Geosyntec) (2.0-2.5) — collected downgradient of the 1985 Ash Pond. After these samples were removed from the dataset, the remaining background soil dataset was re -screened for outliers prior to statistical determinations. A revised background soil dataset identifying valid samples and statistical outliers are presented as Table 1. Currently, the background dataset does not meet the minimum requirement of 10 samples to use formal statistics to derive BTVs. PBTVs were determined 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 constituents in site soil are provided in Table 2. P: \ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination Reports \ Soil \ Cape Fear- SOIL BTV MEMO_FINAL.docx Background Threshold Values- Soil September 5, 2017 Cape Fear Steam Electric Plant Page 3 of 3 NCDEQ requires analytical practical quantitation limit (PQL) soil analytical data be less than the NCDEQ IHSB Preliminary Soil Remediation Goals (PSRG) Protection of Groundwater standards (dated October 2016) for the data to be valid for calculating BTVs. Additional soil samples will be collected to satisfy the minimum number of soil samples and to analyze all constituents by a method whereby the PQL will be below the PSRG Protection of Groundwater values. Once planned additional samples are included in the dataset, the dataset will be screened for outliers and BTVs computed. Sampling of the additional background soil samples is not complete at this time. Therefore, as previously stated, PBTVs were computed and are provided in Table 2. Boring logs and analytical data for subsequent collection of background soil samples will be submitted to the NCDEQ Regional Office if received and processed in sufficient time for review prior to the preparation of the updated CSA report. LIST OF FIGURES: Figure 1 Background Soil Sample Location Map LIST OF TABLES: Table 1 Background Dataset for Soil Table 2 Background Threshold Values for Soil P: \ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination Reports \ Soil \ Cape Fear- SOIL BTV MEMO_FINAL.docx Background Threshold Values- Soil Cape Fear Steam Electric Plant FIGURE September 5, 2017 P: \ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination Reports \ Soil \ Cape Fear- SOIL BTV MEMO_FINAL.docx NOTES: 2016 AERIAL ORTHOPHOTOGRAPHY OBTAINED FROM USDA FSA NAIP VIA ESRI ON 07/18/2017, AERIAL DATED 06/20/2016. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83/2011). MW -22 BGSB-1 r r W22 i BGSB=2 r r 1� Milo �1 MW -9 SB LEGEND e , EXISTING & NCDEQ-ACCEPTED BACKGROUND ® SOIL SAMPLE LOCATION PROPOSED BACKGROUND SOIL SAMPLE LOCATION WASTE BOUNDARY \� COMPLIANCE BOUNDARY i COMBINED COMPLIANCE BOUNDARY NPDES TREATMENT UNIT DUKE ENERGY PLANT BOUNDARY DITCH WITH FLOW DIRECTION STREAM WITH FLOW DIRECTION TOPOGRAPHIC CONTOURS (10' INTERVAL) TOPOGRAPHIC CONTOURS (2' INTERVAL) 400 200 0 400 800 GRAPHIC SCALE IN FEET FIGURE 1 148 RIVER STREET, SUITE 220 BACKGROUND SOIL SAMPLE LOCATIONS PHONEGREENVILLE,SOUTH CARouNA296°1 CAPE FEAR STEAM ELECTRIC POWER PLANT PHONE 864-421-9999 synTerra WWW nterr n0r nnm MONCURE, NORTH CAROLINA DRAWN BY: A. ROBINSON DATE: 08/01/2017 PROJECT MANAGER: K. WEBB CHECKED BY: C. SUTTELL P:\Duke Ener F—ress.1026\00 GIS BASE DATA\Ca e Fear\Ma Docs\Back round\Fi ure 1- Background Soil Sample Locations—d Background Threshold Values- Soil Cape Fear Steam Electric Plant TABLES September 5, 2017 P:\ Duke Energy Progress.1026 \ 103. Cape Fear Ash Basin GW Assessment\ 35.Background Determination Reports \ Soil \ Cape Fear- SOIL BTV MEMO_FINAL.docx TABLE 1 UNSATURATED BACKGROUND SOIL DATA SUMMARY CAPE FEAR STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, MONCURE, NC Analytical Parameter pH Aluminum Antimony Arsenic Barium Beryllium Boron Cadmium Calcium Chloride Chromium Cobalt Copper Iron Lead Magnesium Manganese Mercury Molybdenum Nickel (ats N) Potassium Selenium Sodium Strontium Sulfate Thallium Vanadium Zinc 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 mg/kg I mg/kg mg/kg mg/kg mg/kg mg/kg 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 NE 0.9 5.8 580 63 45 3 NE NE 360000 0.9 700 1 150 270 NE 65 1 NE 130 NE NE 2.1 NE NE NE 0.28 6 1200 Sample ID Sample Collection Date BG -01 (Geosyntec) (2.0-2.5) 08/20/2013 --- 25600 <0.0992 1.61 --- --- 5.26 j <0.053 --- --- 27.2 --- 7.95 --- 19.2 --- 234 0.0387 j --- 4.95 --- --- 0.414 j --- --- --- 0.349 --- 19.8 BG -02 (Geosyntec) (2.0-2.5) 08/20/2013 --- 44400 <0.117 3.32 --- --- 9 j <0.0625 --- --- 40.4 --- 16.8 --- 16.8 --- 134 0.113 j --- 9.2 --- --- 0.795 j --- --- --- 0.347 --- 33 BG -03 (Geosyntec) (2.0-2.5) 08/20/2013 --- 17600 <0.104 2.16 --- --- 6.54 j <0.0554 --- --- 26.9 --- 8.06 --- 12.9 --- 155 0.0536 j --- 3.44 --- --- 0.638 j --- --- --- 0.159 j --- 16.6 MW -09 SB (2-3) 04/25/2015 5.6 7720 --- 8.1 155 1.2 <13.3 <0.64 979 <265 4.3 31.9 8.8 20000 12.4 2500 324 0.007j 3.3 8.4 <26.5 237j 4.4j 166j 15.1 <265 --- 9.7 67.8 MW -09 SB (6-7) 04/25/2015 6.7 9700 --- <5.7 224 0.73 <14.4 <0.69 2750 <291 5 11.4 17.4 24500 26.1 3420 1140 0.012 <2.9 5.7 <29.1 427 --- 338 35.8 <291 --- 10.8 154 MW -22 SB (3-4) 06/10/2016 5.2 15600 --- <1.4 48.4 0.27 --- <0.17 473 <301 D3 17.8 8.2 14.1 16500 6.1 1890 370 0.014 <0.55 7.8 <30.1 H3,D3 139 <1.4 165 7.3 <301 D3 --- 42 28.3 Notes: 54 - Indicates values omitted from dataset. Indicates data removed /identified as an outlier --- - Non -detect value removed from dataset; concentration greater than PSRG Protection of Groundwater < - concentration not detected at or above the adjusted reporting limit. D3 - Sample was diluted due to the presence of high levels of non -target analytes or ther matrix interference. H3 - Sample was received or analysis requested beyond the recognized method holding time. j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit. mg/kg - milligrams per kilogram NA - Not applicable; sample not collected or analyzed NE - Not established PSRG Protection of Groundwater - NCDEQ IHSB Preliminary Soil Remediation Soil Remediation Goals Table - October 2016 S.U. - Standard Units Prepared by: JHG Checked by: MCM P:\Duke Energy Progress. 1026\103. Cape Fear Ash Basin GW Assessment\35. Background Determination Reports\Soil\Table\TABLE 1 - Cape Fear BG Soil 032017 Page 1 of 1 TABLE 2 BACKGROUND THRESHOLD VALUES FOR SOIL CAPE FEAR STEAM STATION DUKE ENERGY PROGRESS, LLC, MONCURE, NC Parameter Reporting Unit PSRG Protection of Groundwater BTVt pH* S. J. NE 5.2 - 6.7 Aluminum mg/kg NE 44400 Antimony mg/kg 0.9 0.117 Arsenic mg/kg 5.8 8.1 Barium mg/kg 580 224 Beryllium mg/kg 63 1.2 Boron mg/kg 45 14.4 Cadmium mg/kg 3 0.69 Calcium mg/kg NE 2750 Chloride mg/kg NE 301 Chromium mg/kg 360,000 40.4 Cobalt mg/kg 0.9 31.9 Copper mg/kg 700 17.4 Iron mg/kg 150 24500 Lead mg/kg 270 26.1 Magnesium mg/kg NE 3420 Manganese mg/kg 65 370 Mercury mg/kg 1 0.113 Molybdenum mg/kg NE 3.3 Nickel mg/kg 130 9.2 Nitrate (as N) mg/kg NE 30.1 Potassium mg/kg NE 427 Selenium mg/kg 2.1 4.4 Sodium mg/kg NE 338 Strontium mg/kg NE 35.8 Sulfate mg/kg NE 301 Thallium mg/kg 0.28 0.349 Vanadium mg/kg 6 42 Zinc mg/kg 1200 154 Prepared by: HHS Checked by: OS Notes; * - Indicates upper and lower limit determined for parameter t - Indicates value is provisional; dataset contains less than 10 valid samples mg/kg - milligrams per kilogram NE - Not Established S.U. - Standard Unit P:\Duke Energy Progress.1026\103. Cape Fear Ash Basin GW Assessment\35. Background Determination Reports\Soil\Table\TABLE 2 - Cape Fear Background Threshold Values Page 1 of 1