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HomeMy WebLinkAboutBackground Dataset_20170707Water Resources Environmental Quality July 7, 2017 Paul Draovitch Senior Vice President Environmental, Health & Safety Duke Energy 526 South Church Street Mail Code EC3XP Charlotte, North Carolina 28202 ROY COOPER Governor MICHAEL S. REGAN Secretary S. JAY ZIMMERMAN Director Subject: Duke Energy Submittal - Background Soil and Groundwater Statistical Methodology for 14 Duke Energy Facilities e-mails submitted May 26, 2017 Dear Mr. Draovitch: The North Carolina Department of Environmental Quality (DEQ) has received and reviewed the May 26, 2017 e-mails from Duke Energy providing background soil and groundwater datasets. These site-specific data were compiled following direction provided in an April 28, 2017 letter from DEQ to address technical concerns related to site assessment and corrective action along with revisions to the Statistical Methods for Developing Reference Background Concentrations for Groundwater and Soil at Coal Ash Facilities (HDR Engineering, Inc. and Synterra Corporation, January 2017) technical memorandum (TM). Attached are reviews of the soil and groundwater datasets for each Duke Energy coal ash facility. These reviews identify data that are appropriate for inclusion in the statistical analysis to determine background threshold values for both media following the methodology outlined in the TM. Additional requirements related to soil and groundwater background determinations are specified for each facility. With approval of these background datasets, preliminary background determinations for each media are expected to be completed and provided within 30 days of receipt of this letter for those facilities that will submit Comprehensive Site Assessments (CSAs) by October 31, 2017. For all other facilities that will submit CSAs later, preliminary background determinations for each media are due within 60 days of receipt of this letter. If you have any questions, please feel free to contact Steve Lanter at (919) 807-6444. Sincerely, S. Jayinlerman, P.G., Director Division of Water Resources Attachments: DEQ Background Dataset Reviews for the 14 coal ash facilities cc: WQROS Regional Offices WQROS Central File Copy State of North Carolina I Environmental Quality I Division of Water Resources Water Quality Regional Operations Section 1636 Mail Service Center I Raleigh, North Carolina 27699-1636 919-707-9129 Allen Steam Station Groundwater • The following background wells are appropriate for use: o BG -1S, BG-2S/D, BG-4S/DBR, GWA-19S, GWA-21SBR, GWA-23S, and GWA-26S/D • The following background wells are NOT appropriate for use: o BG -1D — Recently reinstalled due to water quality issues and reevaluation as background location is necessary before being included. o BG-2BR — Recently reinstalled due to water quality issues and reevaluation as background location is necessary before being included. (Note: while there does appear to be a topographic divide additional evaluation is needed to determine if this is just a shallow divide or if it is indeed a divide for all flow layers.) o AB-4S/DBR — Groundwater elevations below the nearest pond elevation has been observed in several sampling events since installation of AB-4S/D. Due to the potential for groundwater flow from the basin toward/through the well cluster this location should NOT be considered a background location. AB-4BR should also NOT be considered a background location (potential vertical migration from the unconsolidated zone). (Note: Duke will evaluate further regarding pond elevation utilized for assessment.) o GWA-21D —Recently reinstalled due to water quality issues and reevaluation as background location is necessary before being included. • All identified sample event dates are appropriate for use. • The dataset for the shallow flow layer meets the minimum requirement of 10 samples after excluding samples. • The dataset for the deep flow layer does NOT meet the minimum requirement of 10 samples after excluding samples. Additional samples are require . • The dataset for the bedrock flow layer does NOT meet the minimum requirement of 10 samples after excluding samples. Only 4 valid samples, but when additional evaluation regarding nearest pond elevation used for the AB-4S/DBR locations is provided additional samples may be available for inclusion. • All identified outliers are acceptable and should be removed from the background dataset. Soil • The following background samples are appropriate for use: o BG -1D (1.0-2.0), BG -1D (9.0-10.5), BG -1D (19.0-20.5), BG -1D (45-50), BG -2D (1.0-2.5), BG -2D (8.5-10.0), BG -2D (18.0-20.0), BG -3D (1-2.5), BG -3D (13.5- 15), BG -3D (18.5-20), GWA-14D (10.0-12.0), GWA-8D (38.5-40), and GWA-8D (48.5-50) • The following background samples are NOT appropriate for use: o GWA-15D —Sample is at or immediately adjacent to the waste boundary west of the ash storage area and was also collected in fill material (according to boring log). Allen Steam Station Pagel of 2 o GWA-5D —Sample is at or immediately adjacent to the waste boundary east of the ash basin (immediately downgradient) and was also collected in fill material (according to the boring log). • The dataset meets minimum requirement of 10 samples after excluding samples. • The reporting limits for Antimony and Thallium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Allen Steam Station Page 2 of 2 Asheville Steam Electric Plant Groundwater • All identified background wells are appropriate for use. o MW -101 CB -01, CB -09, CB-09SL, MW -24S, CB -011), AMM -03B, and CB-09BR o Duke Energy recommended adding wells GW -1, GW -1D, and GW-1BR to the background dataset. Based on a review of the information provided, these wells may be added to the background dataset. If these wells are added, the new raw background dataset should be re -submitted to DWR. • The datasets for each flow layer meets the minimum requirement of at least 10 samples. • All identified sample event dates are appropriate for use. • All identified outliers are acceptable and should be removed from the background dataset. o If GW -1, GW -1D, and GW -IBR are added to the background dataset then re -test the new dataset for outliers and re -submit to the DWR, including strikethroughs of outliers and other unusable data (e.g high pH, high turbidity, autocorrelated data. Soil • The following background samples are appropriate for use: o CB -01 SB (7-8), CB -01 SB (30-31), CB -09 SB (1-2), CB -09 SB (25-27), GW -01 SB (1-2), MW-11SB (1.5-2), MW -12 SB (1.5-2), MW-13SB (1.5-2), MW-13SB (14.5-15), MW-14SB (1.5-2), MW -22 (1-2), MW-23BR (2-3), and MW-24SB (1- 2) • The following background samples are NOT appropriate for use: o MW -08 and MW -09 — Samples are at or immediately adjacent to the waste boundary and should not be used as background locations, even though the samples were collected above the seasonal high water table. o CB -08, MW -03, MW -05, and MW -07 — Downgradient of site contamination. o MW-13SB (22-22.5) — Sample was collected 3 -feet below the water table and should not be used. • The dataset meets the minimum requirement of at least 10 samples after excluding samples. • The reporting limits for Antimony, Thallium, and Selenium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Asheville Steam Electric Plant Page 1 of 1 Belews Creek Steam Station Groundwater • All identified background wells are appropriate for use: o BG -2S, BG -3S, MW -2025, MW -3, BG -1D, BG -2D, BG -3D, BG -202D, BG-2BR- A, and MW-202BR • The datasets for the shallow and deep flow layers meet the minimum requirement of 10 samples. • The dataset for the bedrock flow layer does NOT meet the minimum requirement of 10 samples. Additional samples are required. • All identified sample event dates are appropriate for use. • All identified outliers are acceptable and should be removed from the background dataset. Soil • All identified background samples are appropriate for use: o BG -1D (1-2), BG -1D (11), BG -1D (21), BG-lD (31), BG -2D (1-2), BG -2D (10- 12), BG -2D (20-22), BG -2D (30-32), BG -3S (1-2), BG -3S (10-12), BG -3S (20- 22), GWA-3D (34-35.5), GWA 4S (45-47), GWA-12D (10-12), GWA-12D (15- 17), GWA-12D (20-22), and GWA-12D (25-27) • The dataset meets the minimum requirement of 10 samples. • The reporting limits for Antimony, Thallium, and Selenium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Belews Creek Steam Station Page 1 of 1 Buck Combined Cycle Station Groundwater • The following background wells are appropriate for use. o BG -18, BG-2S/D, BG-3SBRU, MW-6S/D, GWA-1S, MW -613R, and MW-8S/D • The following background wells are NOT appropriate for use: o BG-1D/BR— Recently reinstalled due to water quality issues and reevaluation as background location is necessary before being included. o BG-2BR — Recently reinstalled due to water quality issues and reevaluation as background location is necessary before being included. o MW-8BR — Recently reinstalled due to water quality issues and reevaluation as background location is necessary before being included. • All identified sample event dates are appropriate for use. • The datasets for each flow layer meets the minimum requirement of 10 samples after excluding samples. • All identified outliers are acceptable and should be removed from the background dataset. Soil The following background samples are appropriate for use: o BG -1D (1-2), BG -1D (9.8-11.2), BG -1D (16.4-17.9), BG -2D (2), BG -2D (10-11.5), BG -2D (13.5-15), BG-3BRU (1-2), BG-3BRU (10-10.5), BG-3BRU (20-20.5), GWA- lOD (3.0), and GWA-11D (19-20.5) The following background samples are NOT appropriate for use: o GWA-11) — Sample was collected from 0.3-0.6 ft. bgs. Per IHSB Guidance, these samples were taken too shallow. o GWA-6BRU — Sample is located downgradient of the Cells 2 and 3 and within 1 foot of the water table. o GWA-7D — Sample is located downgradient of the Cells 2 and 3 and within 1 foot of the water table. o GWA-91) — Sample is located downgradient of Cell 1, both sample intervals were collected in fill material (according to boring log) and one sample interval was collected within 1 foot of the water table. o GWA-12S —Sample is located downgradient of the ash basin. o GWA-22D — Sample is located downgradient of Cell 1 and sample interval was collected in fill material (according to boring log). • The dataset meets minimum requirement of 10 samples after excluding samples. • The reporting limits for Antimony, Thallium, and Selenium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Buck Combined Cycle Station Page 1 of 1 Cane Fear Steam Electric Plant Groundwater • All identified background wells are appropriate for use: o MW-15SU, MW-15SL, MW -16S, MW -09, MW-9BR, MW-15BR, and MW-16BR • The datasets for all flow layers meet the minimum requirement of 10 samples. • The following sample event dates are NOT appropriate for use: o MW-15BR ■ 3/2/16 — Less than 60 days from previous sample. • All identified outliers are acceptable and should be removed from the background dataset. Soil • The following background samples are appropriate for use: o BG-01(Geosyntec)(2.0-2.5), BG-02(Geosyntec)(2.0-2.5), BG-03(Geosyntec)(2.0- 2.5), MW -09 SB(2-3), MW -09 SB (6-7), and MW -22 SB (3-4) • The following background samples are NOT appropriate for use: o MW-05BR SB(0-2), MW -09 SB(0-2), MW-l0BR 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) — Per IHSB Guidance, these samples were taken too shallow. o BG-04(Geosyntec)(2.0-2.5) and BG-05(Geosyntec)(2.0-2.5) — Samples taken down -gradient of 1985 Ash Pond. • The dataset does NOT meet the minimum requirement of 10 samples. Additional samples are required. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Cape Fear Steam Electric Plant Page 1 of I James E. Rogers Energy Complex Groundwater • All identified background wells are appropriate for use. o BG -1S, CCPMW-1S, MW -305, MW -325, GWA-245, GWA-255, GWA-30S, BG - 1D, MW -24D, MW -32D, GWA-24D, MW-32BR, CCPMW-1D, MW-24DR, GWA-24BR, GWA-30BR, MW-22BR, and MW-22DR • The datasets for all flow layers meet the minimum requirement of 10 samples. • All identified sample event dates are appropriate for use. • The following outliers are NOT appropriate for use and should be removed from the background dataset: Soil o Total Dissolved Solids — 10,700,000 ug/L (saprolite) o Total Dissolved Solids — 4,410,000 ug/L (saprolite) o Total Dissolved Solids —407,000 ug/L (transition zone) o Total Dissolved Solids —116,000 ug/L (transition zone) o Iron — 31200 ug/L (transition zone) o Vanadium — 3 ug/L (transition zone) The following background samples are appropriate for use: o BG -1D (3.5-5), BG -1D (8.5-10), BG -2D (3.5-5), BG -2D (8.5-10), BG -2D (18.5- 20), BG -2D (28.5-30), MW -30D (3.5-5.5), MW -30D (8.5-10), MW -30D (18.5-20), MW -30D (28.5-30), MW -32D (3.5-5), MW -32D (8.5-10), MW -32D (18.5-20), MW -32S (22.5-24), MW -42D (28.5-30), and GWA-25D (8.5-10) The following background samples are NOT appropriate for use: o BG -1S (3.5-5), BG -1S (8.5-10), MW -30S (4-5), MW -30S (9-10), MW -30S (19- 20), and MW -30S (28-29), — Only analyzed for TOC. o GWA-1 OD — Located at or immediately adjacent to the waste boundary at Units 1- 4 basin. o GWA-31D (7), GWA-31D (8.7), and GWA-31BR — Located at or immediately adjacent to and downgradient of the waste boundary at Unit 5 basin and are adjacent to a road and parking lot. o MW -38D (33.5-35) — This location is downgradient of the Unit 5 Inactive Ash Basin and adjacent to the Broad River. o GWA-3D (48.5-50) — Location is downgradient of the Unit 5 Inactive Ash Basin. o GWA-12BRU (20-23.5) — Location is immediately downgradient of Units 1-4 Inactive Ash Basin. May be close to water table and is near the Broad River. o GWA-21BRU (5) — This sample may be immediately above the water table and more importantly, the location is potentially downgradient of a basin and is situated adjacent to the Broad River where there a potentially significant fluctuations of water levels by a discharge point. o GWA-22S (3-5) — Location is side gradient of the Active Ash Basin and adjacent to the Broad River. The sample was collected within the screen interval of the well. James E. Rogers Energy Complex Page 1 of 2 o GWA-27D (13.5-15) and GWA-27D (24.9) — Location is adjacent to and downgradient of the impoundment. The sample was collected within the screened interval of the well. o MW-40BRU (3.5-5) — Location is adjacent to and downgradient of the Unit 5 Inactive Ash Basin and near the Broad River, and the sample was collected from within the screened interval. o GWA-61) (28.5-30) — Location is immediately downgradient of Unit 5 Inactive Ash Basin and may be close to water table and is near the Broad River. • The dataset meets the minimum requirement of 10 samples after excluding samples. • The reporting limits for Antimony, Thallium, and Selenium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples for these three parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • The following outlier is NOT appropriate for use and should be removed from the background dataset: o MW -32S (22.5-24) ■ Arsenic — 7.9 mg/kg James E. Rogers Energy Complex Page 2 of 2 Dan River Combined Cycle Station Groundwater • The following background wells are appropriate for use: o GWA-9S, BG -11), GWA-9D, MW -231), MW-23BR, BG -5S, BG -513, BG -10S, BG -101), and BG-10BR o GWA-9S/D and BG- IOS/D/BR appear to be appropriate for use; however, further evaluation will be needed to determine whether these wells are truly located up - gradient of the ash storages. • The following background wells are NOT appropriate for use: o GWA-12S/D —It appears that coal ash constituent boron, have been detected in soil samples taken from this well. o MW-20S/D — This well could be impacted by groundwater flowing from the storage 1 area. • The datasets for the shallow and deep flow layers meet the minimum requirement of 10 samples after excluding samples. • The dataset for the bedrock flow layer does NOT meet the minimum requirement of 10 samples. Additional samples are required. • All identified sample event dates are appropriate for use. o Provisional background threshold value for hexavalent chromium (shallow flow layer), vanadium (shallow flow layer), and radionuclides (shallow flow layer) are based on a limited dataset. Additional samples are required. • All identified outliers are acceptable and should be removed from the background dataset. Soil The following background samples are appropriate for use: o BG -513(1-2), GWA-2D(19-20), GWA-9D(20-21.5), GWA-101)(9-10), SB -1(1-2), SB -1(10-11.5), SB -1(15-16.5), SB -1(20-21.5), SB -1(25-26.5), SB -2(1-2), SB - 2(10 -11.5), SB -2(20-21.5), SB -2(30-31.25), SB -2(35-36), SB -2(65-65.3), SB -3(1- 2), SB -3(10-11), SB -3(20-21.5), and SB -3(35-36.5) The following background samples are NOT appropriate for use: o BG- 1D(0-2) — Per IHSB Guidance, this sample was taken too shallow. o GWA-3D(5-6.5) — Sample taken in close proximity to Ash Storage 1. o GWA-6S(9-11) — Sample taken down -gradient of Ash Basin Primary Cell o GWA-10D(19-20) and GWA-10D(25) — Samples taken down -gradient of Ash Storage 2. o GWA-1113(10-11.5) — Sample taken down -gradient of Ash Storage 1. Th dataset meets minimum requirement of 10 samples after excluding samples. The reporting limits for Antimony, Thallium, and Selenium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary. Dan River Combined Cycle Station Page 1 of 2 • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Dan River Combined Cycle Station Page 2 of 2 H. F. Lee Enerev Complex Groundwater • The following background wells are appropriate for use: o AMW-11S, AMW-12S, AMM -13S, AMW-17S, IMW-01S, IMW-03S, AMW- 11BC, AMW-12BC, AMW-13BC, AMW-16BC, IMW-01BC, IMW-02BC, and IMW-03BC. o AMW-016BC —The location maybe near the contact with the Black Creek. Please confirm. The datasets for the surficial and Cape Fear flow layers meets the minimum requirement of 10 samples. The dataset for the Black Creek flow layer does NOT meet the requirement of 10 samples. Additional samples are required. The following sample event dates are NOT appropriate for use. o AMM -12S ■ 3/1/16 — Less than 60 days from previous sample. o AMW-13S ■ 3/1/16 —Less than 60 days from previous sample. o AMW-12BC ■ 3/1/16 — Less than 60 days from previous sample. o AMW-13BC ■ 3/1/16 — Less than 60 days from previous sample. o IMW-0lBC ■ 3/4/16 — Less than 60 days from previous sample. o IMW-02BC • 3/3/16 — Less than 60 days from previous sample. • All identified outliers are acceptable and should be removed from the background dataset. Soil The following background samples are NOT appropriate for use: o AMW-12 SB (5-6) — Sample may have been taken within 1 foot of the seasonal high water table. o IMW-05 SB (0-2.5) and IMW-05 SB (4-6). This location is in very close proximity to the southeast corner of Inactive Basin 3 and possibly influenced by the presence of the ash basin. Per IHSB Guidance, these samples were taken too shallow. o AMW-18 SB (0-2.5) and AMW-18 SB (3-5). Samples were collected from the core of the plume migrating from the Active Basin. o AMW-04 SB (1-2) and AMW-04 SB (4-5). Samples are located at the western end of the Active Basin, adjacent to the Neuse River. o AMW-16BC (19-21). o AMW-11 (0-2), AMW-12 SB (0-2), AMW-13 SB (0-2), and AMW-16BC (0-2) - Per IHSB Guidance, these samples were taken too shallow. H. F. Lee Energy Complex Pagel of 2 • The dataset does NOT meet the requirement of 10 samples. Additional samples are required. • The reporting limits for Antimony and Thallium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. H. F. Lee Energy Complex Page 2 of 2 Marshall Steam Station Groundwater • The following background wells are appropriate for use. o GWA-4S/D, GWA-5S/D, GWA-6S/D, GWA-8S/D, GWA-12SBR, BG-3BR, MS - 10, MW -4, and MW -4D • The following background wells are NOT appropriate for use: o BG-lBR — Recently reinstalled due to water quality issues and reevaluation as background location is necessary before being included. o GWA-12D — Recently reinstalled due to water quality issues and reevaluation as background location is necessary before being included. • The datasets for each flow layer meets the minimum requirement of 10 samples after excluding samples. • All identified sample event dates are appropriate for use. • All identified outliers are acceptable and should be removed from the background dataset. Soil • The following background samples are appropriate for use: o BG -3D(1-2), BG -313(10-12), GWA-2DA(3-5), GWA-2DA(8-10), GWA-4D(52- 53), GWA-5D(27.5-29.0), GWA-14S(3-5), and GWA-14S(8-10) • The following background samples are NOT appropriate for use: o GWA-IBR — Sample is within the waste boundary downgradient of the ash basin and coal pile. o MW-14BR — Sample is located downgradient of the ash basin and Phase I Landfill (unlined). • The dataset does NOT meet minimum requirement of 10 samples. Additional background samples are required. • The reporting limits for Antimony and Thallium were above the IHSB PSRG Protection of Groundwater values. Additional samples analyzed at a lower detection limit for these parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Marshall Steam Station Page 1 of 1 Mayo Steam Electric Plant Groundwater • The following background wells are appropriate for use: o MW -125, BG -02, MW -12D, BG -01, MW-13BR, and MW-14BR • The following background wells are NOT appropriate for use: o MW-IOBR • The dataset for the surficial flow layer does NOT meet the minimum requirement of 10 samples. Additional samples are needed. • The datasets for the transition zone and bedrock flow layers meets the minimum requirement of 10 samples. o Provisional background threshold values for radionuclides in the transition zone flow layer are based on a limited dataset. Additional samples are required. • The following sample event dates are NOT appropriate for use: o BG -01 Soil ■ 11/3/2015 —Less than 60 days from previous sample. ■ 1/8/2016 — Less than 60 days from previous sample. • 9/8/2016 — Less than 60 days from previous sample. ■ 3/28/17 — Less than 60 days from previous sample. o MW-10BR ■ 1/7/16 —Less than 60 days from previous sample. ■ 9/7/16 —Less than 60 days from previous sample. o MW-13BR ■ 1/7/2016 — Less than 60 days from previous sample. • 9/6/2016 — Less than 60 days from previous sample. All identified outliers are acceptable and should be removed from the background dataset. The following background samples are appropriate for use: o MW-08BR (0.75-1.25), MW-08BR (25.5-26), MW-IOBR (0.75-1.0), MW -12D (1- 2), MW -12D (25-26), SB -01 (1-2), and SB -01 (13.5-14.5) The following background samples are NOT appropriate for use: o MW-03BR (0.8-1.25) and MW-15BR (0.5-1) — Samples taken down -gradient of Ash Basin. o MW-11BR (0-2) and MW-13BR (0-2) —Per IHSB Guidance, these samples were taken too shallow. o SB -02 (0.5-2) and SB -02 (11.0-12.5) — Boring log indicates the presence of coal ash. o SB -03 (5-6) and SB -03 (17-18.5) — Boring log indicates the presence of coal ash. o SB -05 and SB -06. Sample locations were adjacent to the 1981 landfill. The dataset does NOT meet the minimum requirement of 10 samples. Additional samples required. Mayo Steam Electric Plant Page 1 of 2 • The reporting limits for Antimony and Thallium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Mayo Steam Electric Plant Page 2 of 2 Riverbend Steam Station Groundwater • The following background wells are appropriate for use: o BG -1S, MW-7SR, MW -7D, BG -4S, GWA-14S, BG -41), BG -5D, and BG-5BR o MW -71) was listed under the shallow flow laver. Please re-evaluate. • The following background wells are NOT appropriate for use: o GWA-5S — Groundwater water elevations were similar and sometime lower than the historical water elevation of ash basin. Also, the wells are within compliance boundary and not far from the waste boundary. • The datasets for shallow meets the minimum requirement of 10 samples after excluding samples. • The datasets for the deep and bedrock flow layers does NOT meet the minimum requirement of 10 samples. Additional samples are required. • All identified sample event dates are appropriate for use. • All identified outliers are acceptable and should be removed from the background dataset. Soil • The following background samples are appropriate for use: o BG -1D (5-6), BG -1D (14-15), BG -1D (24-25), BG -2D (3.5-5), BG -2D (48-49), BG - 3D (3-5), BG -31) (18.5-20), BG -3D (23-24), GWA-51) (58.5-60), GWA-6D-1(43.5- 45), GWA-6D-2(48.5-50), GWA-21D(3.5-5), GWA-211)(8.5-10), GWA-21D(18.5- 20), GWA-21D(48.5-50), MW-7BR(43.5-45), and OB -2(38.5-40.0) • The following background samples are NOT appropriate for use: o GWA-3D(18.5-19) — Sample taken down -gradient of Ash and Cinder Storage Areas. o GWA-7S(7.0-8.0) — Sample taken down -gradient of Ash Basins. o GWA-8D(8.5-10) — Sample taken down -gradient of Ash Basins. o GWA-9D (1), GWA-10S (8-9), and MW -15D (3.5-5) — Downgradient location and maybe within the High Seasonal Water Table. o GWA-20D(40-41.5) — Sample taken in close proximity to Ash Storage Area. o GWA-22D(38.5-40.0) — Sample taken in close proximity to Ash Storage Area. o GWA-23D(33.5-35) — Sample taken within the waste boundary of the Ash Storage Area. o OB -1(33.5-35.0) — Sample taken inclose proximity to Ash Basin. • The dataset meets the minimum requirement of 10 samples after excluding samples. • The reporting limits for Antimony, Thallium, and Selenium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Riverbend Steam Station Page 1 of 1 Roxboro Steam Electric Plant Groundwater • The following background wells are appropriate for use: o BG -1, MW -15D, MW -18D, BG-01BR MW-IOBR, MW-14BR, MW-15BR, MW- 18BR, and MW-19BRL • The following background wells are NOT appropriate for use: o MW-13BR, MW-16BR, and MW-17BR • The datasets for all flow layers meet the minimum requirement of 10 samples after excluding samples. • The following sample event dates are NOT appropriate for use: o BG -01 ■ 9/8/2016 — Less than 60 days from previous sample. ■ 11/16/16 —Less than 60 days from previous sample. o BG-01BR ■ 7/9/15 — Less than 60 days from previous sample. o MW-17BR • 11/10/16 —Less than 60 days from previous sample. All identified outliers are acceptable and should be removed from the background dataset. Soil • The following background samples are appropriate for use: o MW -08 (14-16), MW -08 (21-23), MW-13BR (22-24), MW-14BR (1-1.25), MW- 14BR (31-31.5), MW-14BR (37.5-38), MW -17 (29-31), MW -18 (31-33), and MW - 18 (37-38) • The following background samples are NOT appropriate for use: o MW -07 (0-2), MW -08 (0-2), MW-IOBR (0-2), MW-13BR (0-2), MW -15 (0-2), MW -16 (0-2), and MW -18 (0-2) — Per IHSB Guidance, these samples were taken too shallow. • The dataset does NOT meet the minimum requirement of 10 samples. Additional samples are required. • The reporting limits for Antimony and Thallium were above the IHSB PSRG Protection of Groundwater values. Samples for these two parameters need to be reported below these values. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. Roxboro Steam Electric Plant Page 1 of 1 �n L. V. Sutton Energy Complex Groundwater • All identified background wells are appropriate for use: o MW -05A, MW -0513, MW -3713, MW -0413, MW -05C, MW -08, MW -37C, MW-05CD, MW -05D, MW -37D, MW -05E, and MW -37E o Lower Surficial Aquifer — An adequate dataset has been provided for all constituents, with the exception chromium (VI). Additional samples are planned for collection to bring the total number of valid chromium (VI) samples to ten by second quarter 2017. • The datasets for the upper and lower surficial flow layer meet the minimum requirement of 10 samples. • The dataset for the Upper Peedee flow layer does NOT meet the minimum requirement of 10 samples. Additional samples are planned for collection to bring the total number of valid samples to ten (second quarter 2017 at the earliest). It was agreed upon to use a pH of less than or equal to 9.7 S.U. as the upper threshold for these zones in the Peedee aquifer. • The dataset for the Lower Peedee flow layer does NOT meet the minimum requirement of 10 samples. New and replacement wells have been added to the groundwater monitoring network (MW -5R -E, MW -8E, MW -41E). Additional samples are planned for collection to bring the total number of valid samples to 10 (second quarter 2017 at the earliest). It was agreed upon to use a pH of less than or equal to 9.7 S.U. as the upper threshold for these zones in the Peedee aquifer. • All identified sample event dates are appropriate for use. • All identified outliers are acceptable and should be removed from the background dataset. Soil • The following background samples are appropriate for use: o AW -02C (10-11) and MW -37C (4-6) • The following background sample are NOT appropriate for use: o AW -01C (0-2), AW -02C (0-2), AW -03C (0-2), AW -04C (0-2), AW -06D (0-2), AW - 07D (0-2), MW -37C (0-2), SMW-01C (0-2), SMW-02C (0-2), SMW-03C (0-2), SMW-04C (0-2), SMW-05C (0-2), and SMW-06D (0-2) — Per IHSB Guidance, these samples were taken too shallow. o AW -05C (4-6) and AW -05C (9-11) —Samples are down -gradient of the ash pond. • The dataset does NOT meet the minimum requirement of 10 samples. Additional samples are require . • The reporting limits for Antimony, Cobalt, and Thallium were above the IHSB PSRG Protection of Groundwater values. Therefore, the number of useable values in the background dataset is severely limited for these constituents. Additional samples analyzed at a lower detection limit for these parameters are necessary. • Please state whether any background sample included fill material. Samples containing fill should be omitted from the raw background dataset. • All identified outliers are acceptable and should be removed from the background dataset. L. V. Sutton Energy Complex Page 1 of 1 W.H. Weatherspoon Power Plant Groundwater • All identified background wells are appropriate for use. o BW -02S, BW -03S, CCR -101-13G, MW -01, BW -03I, and BW -03D • The dataset for the surficial flow layer meets the minimum requirement of 10 samples • The dataset for the Lower Yorktown does NOT meet the minimum requirement of 10 samples. Additional samples are required. • The dataset for the PeeDee does NOT meet the minimum requirement of 10 samples. Additional samples are required. • The following sample event dates are NOT appropriate for use. o BW -03S ■ 3n116 — Less than 60 days from previous sample. • All identified outliers are acceptable and should be removed from the background dataset. Soil No soil background data was provided. Please coordinate the collection of background soil data with the DWR Fayetteville Regional Office. W. H. Weatherspoon Power Plant Page 1 of I