Marshall PT Work Plan FINAL 7-30-20

CAP Pilot Test Work Plan
Marshall 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 is a significant portion of the full-scale corrective action implementation -45% of overall system
Work Plan describes pilot test implementation and data collection activities
Flow rates, area of hydraulic influence, and well spacing
Constituent of Interest (C01) trends
Design modifications from pilot test applied to full-scale system to optimize performance
Obiectives
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
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Pilot Tes'
23 groundwater extraction wells downgradient &
adjacent to Phase I Dry Ash Landfill Area
9 groundwater extraction wells for hydraulic testing
SE of Phase I Dry Ash Landfill
Along Ash Basin dam
8 clean water infiltration wells downgradient &
adjacent to Phase I Dry Ash Landfill Area
Full -Scalp
66 groundwater extraction wells
24 groundwater infiltration wells
Extraction Rate: 0.94 million GPD
Infiltration Rate: 0.41 million GPD
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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 — antimony, barium, beryllium, boron, chloride, cobalt, iron, lithium, manganese, molybdenum,
selenium, strontium, sulfate, thallium, TDS, total radium, and vanadium, Groundwater Draw -Down,
Groundwater Zone of Capture, and Discharge Location — Discharge to ash basin decant system, finally to
NPDES Outfall 002.
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, 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). 5

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.
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Permits
■ Erosion and Sediment Control Permit
(June 2020) —Approved
■ Groundwater Recovery Well Permit (July
2020) —Approved
■ UIC Permit (July 2020) —Submitted,
comments received on 7/7/2020,
Response submitted, NCDEQ comments
received 7/27/20, response in preparation
■ NPDES Permit Modification (November
2020) —Submitted, Draft Permit Received
on i11/2020
■ Lake Services Conveyance Permit (March
2021) — In Progress
Schedul
■ Begin extraction and clean water infiltration well
network installation — August 2020
■ Final Bid Documents— August/September 2020
■ Contracting — September/October 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
■ Pilot test period up to 6 months
■ Scale -up activities — TBD
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