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Home My WebLink AboutAllen PT Work Plan FINAL 7-30-201 plti�F �+ Or '- CAP Pilot Test Work Plan Overview Allen Steam Station (July, 2020) DUKE ENERGY Introduction/Work Plan Objectives Selected Remedy Design Overview Pilot Test Basis of Design Pilot Test Data Collection Objectives Implementation Schedule Pilot test a significant portion of the full-scale corrective action implementation -30% of overall system Describes pilot test implementation and data collection activities Flow rates, area of hydraulic influence, and well spacing Constituent of Interest trends Applied to full-scale system to optimize performance Ob'ective.c Accelerate the corrective action process to meet applicable groundwater standards Optimize the full-scale corrective action system performance based on data collected Focus the pilot test on the most challenging areas at the Site to make immediate progress 3 . - Wz. NhC}Aa � r i r I ACTIVE ASH BASIN NAME 80LTDARY -- • REMED ASH BASIN WASTE BOUNDARY ASH BASIN CeDGRAPHIC LIMITATION RY a&S81 ASH LANDFILLMSTE ---- RETIR.EDAMBASIN ASH. LANDF1LL CORM -LANCE BOUJDWRY ASH STORAGE AREASAND STRUCTURAL FILLS HISTORICAL AND AREARRENi COAL PILE MANAGEMEW--- — DUKE ENERGY CAROLINAS PROPERTY LINE r AREA PROPOSED FOR GRCH NDVVATER L CORRECTIVE ACT10N ROW DRECZION Pilot Tes' 26 groundwater extraction wells along the ash basin dam and to the N and NE of the ash basins and coal piles 4 groundwater extraction wells along the SE bank area for hydraulic testing 20 clean water infiltration wells to the N of the ash basins and coal piles. Full -Scab r- 87 groundwater extraction 82 groundwater infiltration Extraction Rate: 1.4 million GPD Infiltration Rate: 0.55 million GPD 4 O..I 1 _ µ. Mp ,,.I „Aw'' dy gfA 11 I $ IIOAITCR WELL ;SHALLOW ZONE) . ACTIVE ASH BASIN WASTE B04JM MY RETIRED ASH BASIN WASTE BOUNDARY NONNDR WELL ;DEEP ZONE) ASH BASIN GEOGRAPHIC LIMITATION $ MON TOR WELL (BEDROCK ZONE) ■'- - EGEW BASIN ASH LANDFILL WASTE * PRQ�ON 45aL CLUSiHt r RETIRED ASH BASIN ASH LANDFILL PROPOSED SLANTED )"E�CIRAOGTI�1 ON WELL i COMPLIANCE BOUNDARY ■ SUFFACE WATER STI1Jl1G WELL ' ' ASH STORAGE AREAS AND STRUCTURAL 1`11S 10 PROPOSED In�TraanoxWELL I I HISTOR'CALAND CURRENT COAL PILE t PROPOSED SLANTED INFILTRATION WELL � AREA MANAGEMENT AREA MAAF DUKE ENERGY GAROLINAS PROPERTY UNE IDS OUTFALL AGEMENT ED GROLNDJJATER �^" RLOL TEST LOCATTCN �/ CORRECTIVE AICTION+c•�. FI.LLSC.4LE LOCATICIR ouf\E FLOW DRECTKM ENERGY CAROUHAB IYL. Pilot Test — Area Proximate to Coal Pile 26 groundwater extraction wells along the ash basin dam and to the N and NE of the ash basins and coal piles 20 clean water infiltration wells to the N of the ash basins and coal piles. 4 groundwater extraction wells along the SE bank area for hydraulic testing 5 Details — Design Elements Remediation Goals Meet applicable groundwater criteria at and beyond the Geographic Limitation. Applicable standards are North Carolina groundwater standards (NCAC Title 15A, Subchapter 02L, Groundwater Classification and Standards; Interim Maximum Allowable Concentrations; or background threshold values, whichever is greater). Design Objectives COI's — boron, cobalt, iron, manganese, sulfate, strontium, TDS, Groundwater Draw -Down, Groundwater Zone of Capture, and Discharge Location — Discharge to LRB, and finally to NPDES Outfall 006. Design Philosophy Collection points/modular buildings, groundwater extraction equipment, well pump control, clean water infiltration control, well level monitoring, flow monitoring, conveyance, existing utilities/infrastructure, secondary containment, service life, flexibility of equipment, redundancy (spare piping, equipment, etc.), operations and maintenance, and winterization. Instrumentation/Controls Controls Requirements — fail safes to prevent spills/equipment damage and over pressurization, Remote Monitoring, Integration with Facility Operations — interlock with coal yard sump, and Modular Building Communications Extraction Wells Design considerations: number of wells, flow rate, diameter of borehole, material of construction, well pumps, well vaults, and instrumentation. Clean Water Infiltration Wells Design considerations: number of wells, flow rate, diameter of borehole, material of construction, well vaults, riser pipe, and instrumentation. Modular Building Construction (CONEX) and collection tanks (insulated poly -ethylene tank for infiltration and extraction). 6 Overall goal: Generate data needed to verify and refine the design and operation of the full-scale groundwater corrective action system Data collection will focus on performance monitoring to verify conceptual design details, including: Well Capacity - During development of the newly installed extraction and clean water infiltration wells, specific capacity (flow rate divided by drawdown) will be analyzed to select a group of extraction and clean water infiltration wells for further hydraulic testing. Area of Hydraulic Influence and Connectivity - Data will be collected within areas of extraction and clean water infiltration well installation (focus areas) and select hydraulic testing areas to verify hydraulic parameters, horizontal and/or vertical hydraulic gradient control, and influence of clean water infiltration in pore volume exchange. C01 Concentration Reduction - C01 concentration data from historical and pilot test monitoring results will be utilized to evaluate C01 concentration trends and to estimate concentration reduction achieved by hydraulic influence and/or pore volume exchange. Hydrogeology Verification and Constructability - Data will be collected during the pilot test to verify subsurface conditions and to test well constructability and will be used to adjust the full-scale extraction well and/or clean water infiltration well design locations. 7 Permits ■ Erosion and Sediment Control Permit (June 2020) — ,pproved 6/19/2020 ■ Groundwater Recovery Well Permit (July 2020) — Approved 7/7/2020 ■ UIC Permit (July 2020) — Submitted; Request for Additional Info Received 7/7/2020, Response submitted to NCDEQ, Additional comments received 7/27/20 Response in orocess ■ Gaston County Well Permit (July 2020) — Courtesy notification sent. ■ NPDES Permit Modification (January 2021) — No modification needed ■ Dam Safety Permit (July 2020) — No permit required; courtesy notification sent July 7, 2020. Schedule ■ Begin extraction and clean water infiltration well network installation — August 2020 ■ Final Bid Documents —August 2020 ■ Contracting — September 2020 ■ Extraction and clean water infiltration well network installation Complete — November 2020 ■ Extraction well hydraulic testing — January 2021 ■ Construction of extraction and clean water infiltration systems complete — March 2021 ■ Pilot System start-up — April 2021 ■ EMP implementation and pilot test data collection — following start-up ■ Data collection period up to 6 months ■ Scale -up activities - TBD