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Home My WebLink AboutSoil Background Tech Memo REV1_20170526F)� Technical Memorandum Date: Friday, May 26, 2017 Project: Dan River Steam Station To: Melonie Martin From: Jacob Ruffing Subject: Quantification of Valid Background Soil Samples for Statistical Calculations — Revision 1 The purpose of this revised technical memorandum (TM) is to address the North Carolina Department of Environmental Quality's (NCDEQ's) requirement identified below. In addition, this revised TM provides the basis for evaluation of soil samples proposed for use in determining site-specific background concentrations using statistical methods for the Dan River Steam Station (DRSS) as originally presented in the TM dated December 13, 2016. Following submittal of the TM dated December 13, 2016, Duke Energy submitted the Statistical Methods for Developing Reference Background Concentrations for Groundwater and Soil at Coal Ash Facilities (Background Methodology) to NCDEQ on January 20, 2017. NCDEQ subsequently requested additional information regarding the Background Methodology via a letter dated April 28, 2017. As part of the April 28, 2017 letter, NCDEQ requested the following information: Provide up-to-date digital spreadsheets of raw background soil data for each facility by May 26, 2017. Any soil data collected since submittal of the Comprehensive Site Assessments (CSAs) should be included in the table and existing soil data should be reviewed to identify any quality control issues (i.e., sampling intervals, corresponding boring sample ID, etc.) along with identification of outliers and revised accordingly. The up-to-date raw background soil data for background determinations at DRSS are provided in Table 1 of this revised TM. Note the remainder of the requirements in the April 28, 2017 NCDEQ letter are addressed in a revision to the Background Methodology under separate cover. The purpose of this memorandum is to provide the basis for evaluation of soil samples proposed for use in determining site-specific background concentrations using statistical methods. The soil samples evaluated herein were principally collected during CSA fieldwork conducted between March and June 2015. The locations of soil samples evaluated for use in the background determinations are shown on Figure 1. Viability of samples for use in developing background concentrations was evaluated using the following criteria: • Soil sample is collected from a location that is not impacted by coal combustion residuals or coal - associated materials; • Soil sample is collected from a location that is not impacted by other potential anthropogenic sources of constituents; • Soil sample is collected from the unsaturated zone, above the maximum groundwater elevation measured in shallow wells during seven well gauging events conducted between June 2015 and September 2016; and • Soil sample collected from a location not impacted by periodic flooding. A total of 56 soil samples were collected at Dan River during CSA activities. Of these 56 samples, 25 samples satisfy the four criteria listed above and are considered viable samples for use in statistical calculations. These samples were collected from the following locations on-site: BG -1 D, BG -5D, GWA- 2D, GWA-3D, GWA-6S, GWA-9D, GWA-11 D, SB -1, SB -2, and SB -3. Note that viable samples collected from borings near the waste boundary or down -gradient of ash management areas were collected at least one foot above the maximum measured groundwater elevation and are assumed to have not been impacted by groundwater migrating from ash sources. Soil sampling data used in this evaluation, including the range of groundwater elevations for shallow wells in each well cluster and analytical results of soil samples are provided in Table 1. Note that laboratory reporting limit for antimony, arsenic, cobalt, selenium, and thallium exceeded the North Carolina Protection of Groundwater (POG) Preliminary Soil Remediation Goals, as revised in October 2016. -y ✓ GWA-11D DUKE ENERGY IF PROPERTY GWA-11S w -LOS ti GWA-10D <<\ 1�C7 '\ A MW -200S MW -200D ',MW-200SB GWA-1S MW-200BR GWA-ID SB -3 MW -103S mW -1015 MW -103D MW -101D MW -102S AB -1S MW -102D AB -3S ap AV AB -2D AB -3D AB -ID ti AB -2S a ASH BASIN DUKE ENERGY PROPERTY GWA-2D ar GWA-2S M/DDLETOIV Loop AS -5D .5, AS-5SL AS -5S AB-4BR ti AB -4D AB-6SB ti AB -6D AB-6SL AMS MW -203S "W AB-4SL MW -203D AB -4S AB -7D, AMS AB -7S 4000 =Wft A.AB-8SL AB -8D WA -9D -GWA-9S IWAB-9D AB-9SB AMS AB-9BR CHEMICAL POND r fir. GWA-8S PINE HALL ROAD ti pp I ACU LANDFILL I GWA-8D PERMIT NO. 85-03 000 000 000 loom Aw GWA-12S BG -3S 1. GWA-12DGWA-12BR 0 IV BG -3D DUKE ENERGY PROPERTY j LU Ll 4�0 MW -104S MW -104D ae GWA-7 MAIA-7n MW -202S MW -202D 1%,, MWt202BR BG -1D BG-ISB JM"Wftk BG -1S BG-2BR ti BG-2SB BG -2D DUKE ENERGY PROPERTY MW -201D ti GWA-3S 1%, GWA-3D % GWA-4D O isa& L GWA-5D GWA-SBRS GWA-5S GWA-SBR2 OAF s BELEWS CREEKSTVEA ....,,.STATION M BELEWS LAKE ELEVATION 725 FT (APPROXIMATE) Table 1. Analytical Results Analyte Aluminum Antimony Arsenic Barium Beryllium Boron Cadmium Chromium Cobalt Copper Iron Lead Manganese Mercury Molybdenum Nickel Selenium Strontium Thallium Vanadium Zinc Calcium Chloride Magnesium Nitrate Potassium Sodium Sulfate pH (field) Total Organic Carbon CAS RN 7429-90-5 744036-0 7440-38-2 7440-39-3 7440-41-7 7440-42-8 7440-43-9 7440-47-3 7440-48-4 7440-50-8 7439-89-6 7439-92-1 7439-96-5 7439-97-6 7439-98-7 7440-02-0 7782-49-2 7440-24-6 7440-28-0 7440-62-2 7440-66-6 7440-70-2 16887-00-6 7439-95-4 14797-55-8 7440-09-7 7440-23-5 14808-79-8 PH TOC Result Unit m /k mg/kg mg/kg mg/kg mg/kg m /k mg/kg m ik mg/kg m /k m /k m /k mg/kg mg/kg mg/kg m ik m /k m /k mg/kg mg/kg mg/kg mg/kg mg/kg m ik mg/kg mg/kg mg/kg mg/kg Std. Units mg/kg NCDEQ PSRG Industrial Health 100000 94 3 44000 460 46000 200 100000 70 9400 100000 800 5200 8 1200 4400 1200 100000 2.4 1200 70000 NS NS NS 100000 NS NS NS NS NS NCDEQ PSRG Protection of Groundwater NS 0.9 5.8 580 63 45 3 360000 0.9 700 150 270 65 1 NS 130 2.1 NS 0.28 6 1200 NS NS NS NS NS NS NS NS NS Sample Name Sample Date Range of Depth-to- Water (ft) BG-1 D(0-2) 5/19/2015 12.35 - 13.74 7980 J 7,9-111 7.9 UJ 51.8 J+ 0.46 19.8 U 0.95 U 15.5 5.6 J+ 12.1 16500 10.8 J+ 177 0.033 4 U 4.6 5 911 6.7 7-:9-111 27.9 20.6 475 367 U 1290 J+ 36.7 UJ 486 395 U 367 U 5.2 J 7020 BG-5D(1-2) 5/27/2015 2.49-5.21 13200 rap 3.9 J. 57.8 J+ 0.56 15.7 UJ 0.75 UJ 40.2 J- 6.8 J- 21.7 30400 15.1 113 0.026 3.1 U 7.4 6.3 R 6.5 62-111 45.9 26.7 248 325 U 1110 32.5 UJ 684 314 U 325 U 5.1 J 1560 GWA-21)(19-20) 5/12/2015 20.85 - 22.53 19500 5611 3:5.J 207 2 14.4 U 0.69 UJ 30.6 18.6 41 48300 13.5 468 0.006 J 2.9 U 29.9 32J 19.5 5-811 30.2 139 908 277 U 4520 27.7 UJ 1790 288 U 277 U 6.7 J 556 J GWA-3D(5-6.5) 4/6/2015 18.45 - 18.82 8390 5-:5-U 5.5 U 44.6 1.6 13.9 U 0.67 U 12.7 7.1 41.4 27600 20 83.7 0.0051 J 4.3 7.7 a,6-U 2.8 U 3-,5-U 11.3 41 139 U 284 U 429 28.4 UJ 353 277 U 284U 5.5 J 543 J GWA-6S(9-11) 6/12/2015 12.51 - 15.11 2610 6x-11 6.1 U 31.9 0.16 J 15.3 U 0.74 U 8.9 3.5 J 4.4 5260 3.8 J 97.9 0.0072 J 3.1 U 3.2 6-1-11 3.6 a 111 12.1 11.9 298 304 U 987 30.4 UJ 745 307 U 254 J 51 NA GWA-91)(20-21.5) 5/13/2015 21.93 - 28.82 9620 6 4 5.4 U 34.2 0.64 13.4 U 0.64 UJ 18.8 10.5 6.4 16500 11.6 267 0.0094 1.6 J 6.7 441 2.3 J 3-411 15.5 23.5 77.4 J+ 276 U 930 27.6 UJ 579 269 U 276 U 5.2 J 490 J GWA-10D(9-10) 5/5/2015 26.68 - 26.98 19900 6.7 J 5.7 U 103 2.9 14.3 U 0.69 U 14.9 18.6 12.5 27500 13.5 247 0.0096 U 2.9 U 19.4 6-7 U 7.7 6.7 U 26.6 67 185 287 U 3300 28.7 UJ 1950 286 U 287 U 5.5 J 509 J GWA-10D(19-20) 5/5/2015 26.68 - 26.98 16200 611 6 U 140 1.4 15.1 U 0.73 U 67.1 11.1 61.3 40000 14.1 376 0.0099 U 12.1 24.3 6-11 27.9 6-11 20.8 78.3 1120 293 U 3730 29.3 UJ 1270 302 U 293 U 6 J 521 J GWA-10D(25) 5/5/2015 26.68 - 26.98 18500 521, 5.3 U 130 1.4 13.3 U 0.64 U 20.2 16.1 10.8 40100 15 373 0.0081 U 2.7 U 32.3 3J 55 3:3-11 22.5 1 112 2100 257 U 5880 25.7 UJ 1560 266 U 257 U 6.2 J 451 J GWA-11 D(10-11.5) 3/21/2015 15.70 - 17.52 12300 2$11 2.8 U 75.9 1.1 20.9 0.33 U 9.9 9_5 8.6 16900 19.2 233 0.0074 J 2.8 UJ 8.5 3_3 5 2-8-11 21.4 25.2 99.4 J 291 U 2080 29.1 UJ 184 J 277 U 291 U 51 801 SB-1(1-2) 5/2/2015 35" 22200 62111 4J- 63.6 J+ 0.72 17 UJ 0.81 U 21.9 7 J+ 21.9 41800 13.9 J- 113 0.047 3.4 U 9 63111 8.6 6.8-U 39.9 40.1 172 338 U 1560 J+ 33.8 UJ 635 339 U 338 U 4.6 J 20400 SB-1(10-11.5) 5/2/2015 35' 33200 5-:6-U 4.6 J 59.6 3.9 14 U 0.67 U 32.7 18.9 44.6 95900 25.9 418 0.0069 J 2.8 U 52.2 5611 1.9 J 5§11 49.5 178 140 U 267 U 6110 26.7 UJ 168J 280 U 267 U 4.9 J 1080 SB-1(15-16.5) 5/2/2015 35' 23600 611 3.1 J 51.6 2.7 15.1 U 0.72 U 19.9 16.2 25.1 54700 18.4 202 0.0052 J 3 U 27.5 6-11 3.2 6-11 38.7 107 151 U 287 U 4050 28.7 UJ 247 J 301 U 287 U 5.3 J 1280 SB-1(20-21.5) 5/2/2015 35' 27600 5811 5.3 J 74.8 2.2 14.8 U 0.71 U 28.5 14.6 47.9 54800 14.9 145 0.04 3 UJ 17.1 SSU 21.8 6.9 U 54.4 70.5 269 285 U 4050 28.5 UJ 605 297 U 285 U 5.4 J 12300 SB-1(25-26.5) 5/2/2015 35' 18700 5:5-11 20 73.8 1.7 14.1 U 0.44 J 17 26.2 79.5 39300 31.3 328 0.038 7.4 38.9 56-11 78 5611 19.1 178 9480 293 UJ 4690 29.3 UJ 1340 282 U 243 J- 4.5 J 13500 SB-2(1-2) 4/14/2015 NE 14000 6311 6.3 U 110 1 2 15.7 U 0.76 U 20.3 13 27.7 30300 12.3 233 0.0092 UJ 3.1 U 12.6 1 6311 10.3 1 6,3-11 21.3 51.1 429 300 U 2360 30 UJ 1280 315 U 300 U 7.2 J 1 637 J SB-2(10-11.5) 4/15/2015 NE 27700 5:8-11 5.8 U 110 2.1 14.5 U 0.69 U 30.9 12 57 49100 21.5 256 0.012 2.9 U 19.1 5-.B-U 4.4 543-11 41.4 83.5 145 U 284 U 4490 28.4 UJ 2730 289 U 284U 5.5 J 718 SB-2(20-21.5) 4/15/2015 NE 24300 5-9-11 10.6 211 1.9 14.8 U 0.71 U 111 42.6 66.1 60300 18.9 1150 0.024 5.4 36.3 5-9-11 73.9 5-9-11 33.8 104 1930 289 U 4790 28.9 UJ 2100 297 U 289 U 5.3 J 7430 SB-2(30-31.25) 4/15/2015 NE 17400 SSU 9.2 71.3 1 14.7 U 0.71 U 34.7 20.1 68.4 1 42700 18.2 395 0.0086 J 3.2 32.4 5911 36.4 5911 24.2 113 4160 285 U 8470 28.5 UJ 2200 295 U 145 J 6.5 J 14500 SB-2(35-36) 4/15/2015 NE 19800 Fi 4 5.4 U 61.9 0.59 13.5 U 0.65 U 27.1 12 30.2 37100 11.4 837 0.0073 J 1.9 J 19.4 5-0-11 52.8 5-0-11 26.2 74.1 9850 279 U 10800 27.9 UJ 1800 269 U 279 U 8.6 J 3680 SB-2(65-65.3) 4/15/2015 NE 24600 6-1-11 8.6 74.4 0.86 15.2 U 0.73 U 36.1 21.8 57.8 49200 16.5 433 0.011 1.6 J 31.9 6x-11 60.7 6-1-11 34.1 91.4 10200 291 U 12700 29.1 UJ 1970 160 J 291 U 8.6 J 20100 SB-3(1-2) 4/17/2015 40' 14300 6SUJ 7J 102 1.6 16.5 U 0.79 U 18 8.9 J- 26.9 33600 21.9 200 0.017 3.3 UJ 9 9 6 11 7.1 6511 37.3 58.2 680 322 U 1830 J- 32.2 UJ 1390 329 U 504 4.2 J 1570 SB-3(l 0-11) 4/18/2015 40' 15000 6:411 6.4 U 104 1.2 16 U 0.77 U 19.3 16.1 23.3 27700 23 601 0.03 3.2 U 12 64-11 13 6.4-U 35 46.5 1480 322 U 3060 32.2 UJ 1700 320 U 322 U 5 J 6120 J+ SB-3(20-21.5) 4/18/2015 40' 17700 53U 5.8 U 63 1.5 14.5 U 0.7 U 17.7 7_5 23.4 28800 17.8 82.7 0.0052 J 2.9 U 16.9 F.8 I I 25J 543-11 34.3 61.1 433 280 U 2330 28 UJ 308 290 U 280 U Al7. 83 J SB-3(35-36.5) 4/18/2015 40' 12100 6:5-1 6.5 U 89.7 0.75 35.9 J 0.79 U 12.8 22.6 15.6 34400 22.9 2840 0.011 U 3.3 U 21.9 63-11 24.2 6311 21.5 47.8 2010 339 U 2430 33._9U J 313 J 327 U 339 U J 862 otal Number of Viable Soil Samples >1 25 0 25 25 25 25 25 25 1 25 25 25 25 25 25 25 1 25 3 25 0 25 25 25 25 25 25 25 25 25 25 35 General Notes: Depth -to -Groundwater data was collected in: 6/15, 9/15, 11/15, 12/15, 4/16, 6/16, and 9/16 "Strike-throughs" indicates samples that will not be used in the initial background dataset for determining proposed provisional background threshold values (PPBTVs) The criteria for "strike-throughs" (as stipulated by NCDEQ) requires Duke Energy to omit samples resulting in non -detect values higher than the Provisional Soil Remediation Goal for Protection of Groundwater - Depth -to -Water measurement collected at time of drilling NE - Not Encountered mg/kg - milligrams per kilogram NA - Not analyzed or not reported by analytical laboratory Std. Units - pH units Comparison Criteria: NS - No applicable standard for this parameter Shading indicates exceedance of either applicable criteria. bold - indicates exceedance of NCDEQ Industrial Health Based PSRG Italic/underfine- indicates exceedance of NCDEQ Protection of Groundwater PSRG North Carolina Department of Environmental Quality Division of Waste Management Soil Remediation Goals Table (October 2016) - Preliminary Industrial Health Based Soil Remediation Goal (PSRG) and Protection of Groundwater PSRG. "Note: No PSRG for Total Chromium is currently available, as a surrogate the PSRG for Trivalent Chromium was used for comparison purposes only. Qualifier Notes: U -- Not detected above the reporting detection limit. J -- Estimated Concentration J+-- Estimated concentration, biased high. J- --Estimated concentration, biased low.