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Home My WebLink AboutAVL Coal Pile Soil Asmt Tech Memo - 2020 Soil Sampling_20200401TECHNICAL MEMORANDUM Date: April2020 File: 1026.102.76 To: Bryson Allison (Duke Energy) Cc: Kathy Webb (SynTerra) From: Grant Barrier 6'4 Subject: Coal Pile Unsaturated Soil Assessment - Asheville Steam Electric Plant Duke Energy Progress, LLC (Duke Energy) owns the Asheville Steam Electric Plant (Plant or Site) in the town of Arden in Buncombe County, NC. The Site encompasses approximately 786 acres. Coal-fired power generation operations began in 1964 with the construction of two coal-fired power generating units. The Plant also has two combustion turbines that are currently operational. The coal-fired units were replaced by natural gas combined cycle energy production in early 2020 and the coal fired facility is currently being decommissioned. Consequently, the coal pile that was stored on approximately 7.6 acres immediately south of the former power generation units is being removed. Groundwater and soil assessment activities for the coal pile began in 2018 with the installation of monitoring wells around the perimeter of the coal pile during 2018 and 2019. Those initial assessment activities identified an area of low pH in groundwater near the southwestern corner of the coal pile, which may be caused by historical storage of coal rejects (pyrite) in this area. Unsaturated soil directly beneath the coal pile could not be assessed during operation of the facility and is considered a data gap for the coal pile assessment. Planned assessment activities for unsaturated soil directly beneath the coal pile at the Site is described herein. Coal Pile Unsaturated Soil Assessment Objectives Objectives of the coal pile area assessment for unsaturated soil underlying the coal pile include the following: Characterize inorganic constituents associated with unsaturated soil beneath the coal pile; • Compare inorganic constituent concentrations in unsaturated soil beneath the coal pile to NC Preliminary Soil Remediation Goals (PSRGs) for protection of groundwater (POG) and site background soil data; Coal Pile Unsaturated Soil Assessment Tech Memo April 2020 Asheville Steam Electric Plant Page 2 of 4 • Further evaluate soil as a potential source of low pH groundwater near the southwestern corner of the coal pile. Regulatory Background In 2014, The North Carolina General Assembly passed the Coal Ash Management Act (CAMA). CAMA required owners of a coal combustion residuals (CCR) surface impoundment to conduct detailed assessment of site groundwater within and around the CCR surface impoundment. As indicated in a letter from the North Carolina Department of Environmental Quality (DEQ) dated September 8, 2017, it is understood that in addition to CAMA requirements, Duke Energy is also bound by the rules and requirements of the NC General Statutes and NC Administrative Code 02L. These provide requirements for the assessment and abatement of soil and groundwater effects resulting from site activities. Therefore, Duke Energy must ultimately address soil and groundwater effects resulting from primary and secondary sources at the coal ash facilities, not just the CCR surface impoundments. Pursuant to the September 2017 DEQ letter, Duke Energy understands the former coal pile area soils and underlying groundwater to be a potential "secondary source" of inorganic constituents that will be assessed apart from CAMA. However, as indicated in a letter from DEQ to Duke Energy dated February 26, 2020, the assessment of primary and secondary sources (including the raw coal pile) will be included in the upcoming CAMA Comprehensive Site Assessment (CSA) Update along with an updated assessment of the impoundments. Site Description The Asheville Plant is situated on the shore of Lake Julian. Lake Julian provides cooling water to the plant and was formed by damming the flow of Powell Creek on the north side of the Plant. A large portion of Lake Julian borders the east side of the Site. Surface water from the French Broad River is also pumped into Lake Julian as a supplemental water supply. The water from the French Broad River enters a stilling area of the lake on the north side of the Plant. Heated water is discharged back into Lake Julian to the east of the Plant. The coal pile is centrally located within the Plant operations. The land surface of the coal pile and the land surface surrounding the coal pile is relatively flat and is at an elevation of approximately 2,171 to 2,173 feet North American Vertical Datum of 1988 (NAVD 88). Surface water runoff from the coal pile and surrounding areas is directed to the 1964 coal ash basin by ditches and similar engineered drainage features. Coal Pile Unsaturated Soil Assessment Tech Memo April 2020 Asheville Steam Electric Plant Page 3 of 4 Unsaturated SoH Assessment Unsaturated soil directly beneath the coal pile will be sampled and analyzed for inorganic parameters to determine if it is a secondary source of coal pile constituents that can leach into underlying groundwater. Soil samples will be collected at five (5) proposed soil boring locations. One (1) location is proposed in the approximate center of the coal pile. The remaining four (4) locations are proposed radially approximately 150 to 200 horizontal feet from the proposed center location. The proposed locations of the soil borings are included as Figure 1. Proposed locations are approximate and may vary slightly based on field observations and accessibility which will be determined prior to initiation of boring activities. If warranted, up to five (5) additional soil boring locations may be sampled if field observations of the proposed locations indicate the need for further investigation. The necessity and locations of these potential soil borings will be determined in the field. Observations that could warrant further investigation beyond the five (5) proposed soil boring locations include, but are not limited to: • Coal like material or staining present beneath several feet or more of soil visually determined to be free of overburden coal; • An unanticipated change in soil type or presence of pyrite that could indicate a historical storage area that has been regraded; and • Other anomalies or staining that would suggest the need for further investigation, based on professional judgement. Soil samples will be collected from 2 to 3 feet below ground surface (bgs) beneath the coal pile and at approximately 2-foot intervals to the top of the groundwater table or bedrock, whichever is encountered first. Soil samples will be analyzed for inorganic parameters consistent with assessment of areas used for coal and CCR management (Table 1). Samples will also be collected for Synthetic Precipitation Leaching Procedure (SPLP) analysis at a frequency of 2 per soil boring location from near ground surface (2 to 3 feet bgs) and approximately 2 to 3 feet above the groundwater table or bedrock, whichever is encountered first. The SPLP analysis will assess the leaching potential of select constituents of interest (COIs) in soil to the underlying groundwater. In addition to SPLP and inorganic parameters listed in Table 1, additional analyses are proposed for soil boring location(s) that exhibit low pH to further evaluate soil as a potential source of low pH groundwater near the southwestern corner of the coal pile. SynTerra would collect field readings of pH by making a paste aliquot and measuring pH with a calibrated pH probe. The paste aliquot would be made by mixing deionized Coal Pile Unsaturated Soil Assessment Tech Memo April 2020 Asheville Steam Electric Plant Page 4 of 4 water with solids collected at selected intervals from the boring(s). Based on field screening results, additional samples would be collected from low pH intervals and submitted for laboratory analysis for further characterization. Those samples would be analyzed for the following parameters: • pH - to assess the acidity or alkalinity of the material and verify field measurements recorded with the pH probe • Acid base accounting - to determine the acid -producing and acid -neutralizing potential of the material • Acid volatile sulfide - to assess constituent concentrations liberated during acidification of the material • Inorganic and mineralogical analysis - to assess the chemical composition and mineralogy of the material • SPLP - to further assess leaching potential of material collected at intervals that exhibit low pH • Hydrous iron oxide/hydrous aluminum oxide (HFO/HAO) - to assess the available area for constituent sorption to the material Soil boring total depths are estimated to be approximately 30 feet below ground surface, based on review of data from nearby Coal Pile Assessment (CPA) monitoring wells. To supplement data that will be used for the geochemical model in the corrective action plan (CAP), additional solid (soil or bedrock) samples may be collected near the southwest corner of the coal pile at depths that coincide with the screened intervals of CPA-4D (10-20 feet bgs) and CPA-4BR (31-41 feet bgs) for HFO/HAO analysis. Actual soil boring total depths will be determined in the field based on field observations. Sonic drilling is recommended as the method of installation of the soil borings due to the quality of continuous cores produced for subsurface characterization purposes. Continuous soil cores will be collected from the ground surface to the top of bedrock to accurately document the underlying stratigraphy, collect relatively undisturbed soil samples from predetermined depths, and to identify any anomalies that may be preset that could warrant further investigation Coal Pile Unsaturated Soil Assessment Reporting Results of the coal pile unsaturated soil assessment are planned to be incorporated into the upcoming CSA, with an anticipated submittal of December 2020. Attachments: Table 1 Soil Analytical Parameters Figure 1 Proposed Coal Pile Unsaturated Soil Boring Locations Coal Pile Unsaturated Soil Assessment Tech Memo April 2020 Asheville Steam Electric Plant FIGURE - lay Jill i -,- r �, r�" I,.: ur•.-- Ilk. - 1 Ir- Ell 11 •; cur `� ` �r '{f t air till Ir t 1 ,r ..F _ r r CPA-1 D 91 A All a ' r • I - r, pl ' � •r y�l roe _�n '9► IL; _COAL PILE AREAs 61111L�Il ' Cr—PA-6D CPA-66R L � •. r, :71 ' ➢�% '� ' �, ti CPA-4D LEGEND !' / r�/�` -z ` r .>� ` Y s�� , .,.' F34��,- ♦ PROPOSED UNSATURATED SOIL BORING IiP WELL IN TRANSITION ZONE �P WELL IN BEDROCK ZONE I '' y CPA -SD CPA-5BR WELL `, t �o . /j f a j• •rl ^; ASH BASIN WASTE BOUNDARY 41 ASH BASIN COMPLIANCE BOUNDARY d s !w ~I CPA-3D f, / ' • DUKE ENERGY PROGRESS PROPERTY LINE r I�N _ p. �t '"_.J -I�r ® NOTES: f� ti k •- '�#� ��AI I .` CPA-3BR 1. AERIAL PHOTOGRAPHY OBTAINED FROM NORTH CAROLINA ONE MAP ON APRIL 7, 2020. AERIAL DATED JANUARY 1, 2019. 7 \ r •`- : 'G = 2. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FPS 3200 (NAD83). GRAPHIC SCALE DUKE 7s o 75 150 FIGURE 1 ;# ENERGY IN FEET) PROGRESS PROPOSED COAL PILE UNSATURATED SOIL - I DRAWN BY: C.DAVIS DATE:05/03/2019 BORING LOCATIONS CHECKED REVISED C.DAVIS DATE 04/07/2020 2020 EVILLE ASH STEAM ELECTRIC PLANT APPROVED BY: DATE: 04/07/2020 ARDEN, NORTH CAROLINA PROJECT MANAGER: G. BARRIER s. = synTerra www.synterracorp.com Coal Pile Unsaturated Soil Assessment Tech Memo April 2020 Asheville Steam Electric Plant TABLE TABLE 1 SOIL ANALYTICAL PARAMETERS COAL PILE UNSATURATED SOIL ASSESSMENT TECH MEMO ASHEVILLE STEAM ELECTRIC PLANT DUKE ENERGY PROGRESS, LLC, ARDEN, NC Inorganic Compounds PSRG POG Units Method Aluminum 110000 mg/kg EPA 6010D Antimony 0.9 mg/kg EPA 6020B Arsenic 5.8 mg/kg EPA 6020B Barium 580 mg/kg EPA 6010D Beryllium 63 mg/kg EPA 6020B Boron 45 mg/kg EPA 6010D Cadmium 3 mg/kg EPA 6020B Calcium NE mg/kg EPA 6010D Chloride* NE mg/kg EPA 9056A Chromium 3.8 mg/kg EPA 6010D Cobalt 0.9 mg/kg EPA 6020B Copper 700 mg/kg EPA 6010D Iron 150 mg/kg EPA 6010D Lead 270 mg/kg EPA 6020B Magnesium NE mg/kg EPA 6010D Manganese 65 mg/kg EPA 6010D Mercury 1 mg/kg EPA 7471B or 7470A Molybdenum 7.1 mg/kg EPA 6010D Nickel 130 mg/kg EPA 6010D Nitrate as Nitrogen* NE mg/kg EPA 9056A pH* NE S.U. EPA 9045D Potassium NE mg/kg EPA 6010D Selenium 2.1 mg/kg EPA 6020B Sodium NE mg/kg EPA 6010D Strontium 1500 mg/kg EPA 6010D Sulfate* NE mg/kg EPA 9056A Thallium (low level) 0.28 mg/kg EPA 6020B Total Organic Carbon* NE mg/kg EPA 9060A Vanadium 350 mg/kg EPA 6020B Zinc 1200 mg/kgmg/kg EPA 6010D Prepared by: GAB Checked by: TDP Notes: 1. Soil samples to be analyzed for Total Inorganics using USEPA Methods 6010/6020 and pH using USEPA Method 9045, as noted above. 2. Select soil samples collected from near ground surface (2 to 3 feet) and from just above the water table or bedrock (field determined) in each boring will also be analyzed for leaching potential using SPLP Extraction Method 1312 in conjunction with USEPA Methods 6010/6020. 3. Analytical methods as presented were applicable as of May 6, 2019. Analytical methods are updated periodically and applied as appropriate. * Select constituents are not analyzed for leaching potential. PSRG POG - Preliminary Soil Remediation Goals for Protection of Groundwater mg/kg - Milligrams per kilogram S.U. - Standard Unit Page 1 of 1