Roxboro PT Work Plan FINAL 7.30.20

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CAP Pilot Test Work Plan
Roxboro Stearn electric Plant k,,uly 2020)
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ENERGY

Introduction/Pilot Test Objectives
Selected Remedy Design Overview
Pilot Test Basis of Design
Pilot Test Data Collection Objectives
Implementation Schedule

Pilot test represents a significant (-50%) portion of overall full-scale system corrective action
implementation
Work Plan describes pilot test implementation and data collection objectives and activities
Flow rates, area of hydraulic influence, and well spacing
Constituent of Interest (COI) trends
Pilot test data will be applied to full-scale system to optimize performance
Obiectivef
Pr Accelerate the corrective action process to meet applicable groundwater standards
Focus the pilot test on the most challenging areas at the Site to make immediate progress
Collect system performance data to allow optimization of the full-scale corrective action
system
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Pilot Test
41 vertical extraction wells near the
Geographic Limitation of Source Area 1
(East Ash Basin)
Total Combined Extraction Rate: 50 gpm
Full -Scale System (current Design)
59 groundwater extraction wells
41 near the Geographic Limitation of
Source Area 1
18 near Source Area 3 (Gypsum Storage
Area)
27 clean water infiltration wells near
Source Area 3
# Sump Area
Proposed Full Scale Extraction Wells
Proposed Node Budding =Industrial Landfill Area with
Proposed Pilot Test Extraction Wei � Pilot Study Node 9Lidding Engineered Liner System
Conveyance Path r.-MGeograpW Limitation
F svrg kionitaring h4ell — Extraction Well Conveyance Path � RDxbx.o Steam Electric Plant
Property Line
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Rernediation 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 • Achieve groundwater extraction rate of —50 gpm to establish groundwater draw-down/capture zone, based
Objectives/Approach on modeled extraction well spacing of —45-75 feet.
• Pressure transducers with PLC control set points in each well will automate pump cycling to maintain
targeted draw -down.
• Extracted groundwater pumped from individual wells to collection points/node buildings with secondary
containment, then conveyed to existing Silo 5 Sump, which leads to treatment and final discharge to
NPDES Outfall 003.
Instrumentation/Controls • Controls Requirements — minimize complexity, include fail safes to prevent spills/equipment damage and
over pressurization, allow for automated operation and remote monitoring.
• Groundwater extraction well pump controls, well level/flow monitoring equipment, water collection tank,
and secondary containment all contained within node buildings to facilitate operations and maintenance,
and winterization.
Vertical Extraction Wells • Pilot test design includes 41 vertical extraction wells, 6" diameter (10" borehole), each including'/2-1 HP
electric submersible pumps and pressure transducers to automate pump cycling.
• Modeled individual extraction well flow rates ranging from 0.1-2.4 gpm.
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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 wells, specific capacity (flow rate divided by
drawdown) will be analyzed to select a group of extraction wells for further hydraulic testing.
Area of Hydraulic Influence and Connectivity - Data will be collected within areas of extraction well installation
(focus areas) and select hydraulic testing areas to verify hydraulic parameters, and horizontal and/or vertical
hydraulic gradient control.
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.
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.
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Permits
■ Erosion and Sediment Control Permit
Approved June 2020
■ Groundwater Recovery Well Permit
Approved July 2020
Schedule (Estimated Completion Dates)
■ Extraction Well Installation — August 2020
■ System Installation Contracting —
September/October 2020
■ Pilot System Construction complete — March 2021
■ Pilot System Start-up — March/April 2021
■ EMP Implementation/Pilot Test Data Collection —
on -going following start-up
■ Pilot test period up to six months
■ Scale -up Activities - TBD
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