2016-05-13 Marshall_Bedient Report

REMEDIATION OF SOIL AND GROUNDWATER
AT THE
MARSHALL STEAM STATION
OPERATED BY DUKE ENERGY CAROLINAS, LLC
TERRELL, NORTH CAROLINA
Expert Opinion of:
Philip B. Bedient, Ph.D., P.E.
P.B. Bedient and Associates, Inc.
P.O. Box 1892
Houston, Texas 77251
713-303-0266
13 May 2016

13 May 2016
REMEDIATION OF SOIL AND GROUNDWATER
AT THE
MARSHALL STEAM STATION
OPERATED BY DUKE ENERGY CAROLINAS, LLC
TERRELL, NORTH CAROLINA
TABLE OF CONTENTS
1.0 Introduction........................................................................................................................ 1
1.1 Summary of Opinions......................................................................................................... 1
1.2 Qualifications......................................................................................................................1
2.0 Summary of the HDR CSA and CAP Part 1 & 2 ............................................................ 2
2.1 Physical Setting...................................................................................................................2
2.2 Hydrogeology..................................................................................................................... 3
2.3 Marshall Coal Ash Basin and Coal Combustion Products (CCP) Landfill ........................ 3
2.4 Contamination.....................................................................................................................3
3.0 Efficacy of Remedial Options for Coal Ash Contaminants Evaluated by HDR.......... 4
3.1 Excavation and Removal.................................................................................................... 4
3.2 Cap-In-place........................................................................................................................5
4.0 Opinions..............................................................................................................................5
4.1 The remediation scenarios evaluated by HDR will not cause groundwater
standards to be met inside the compliance boundary, cause groundwater
standards to be met beyond the compliance boundary, or prevent coal ash
contaminants from migrating across the compliance boundary and into Lake
Norman for the foreseeable future...................................................................................... 5
4.2 Successful remediation of groundwater will require excavation and removal
coupled with additional measures, such as hydraulic groundwater containment ............... 5
5.0 References...........................................................................................................................6
Remediation of Soil and Groundwater Expert Opinion of
Marshall Steam Station, Terrell, NC i Philip B. Bedient, Ph.D., P.E.
1261

13 May 2016
REMEDIATION OF SOIL AND GROUNDWATER
AT THE
MARSHALL STEAM STATION
OPERATED BY DUKE ENERGY CAROLINAS, LLC
BELMONT, NORTH CAROLINA
1.0 Introduction
I was retained on this project for the purpose of evaluating remediation of soil and groundwater
at the Duke Energy Carolinas, LLC (Duke) Marshall Steam Station (the "site") coal ash disposal
facilities. In particular, I have focused my analysis on different methods of preventing continued
transport of coal ash contaminants across the compliance boundary in groundwater at
concentrations that exceed relevant groundwater standards. The compliance boundary' is the
regulatory boundary established for measuring compliance with applicable water quality
standards by the North Carolina Department of Environmental Quality (NCDEQ). The relevant
standards are:
• 15A NCAC 02L.0202 Groundwater Quality Standards (2L Standards); and,
• 15A NCAC 2L.0202(c) Interim Maximum Allowable Concentrations (IMACs)
established by the NCDEQ, which apply to groundwater locations beyond the limits of
the ash basins.
My opinions are based on my professional experience in hydrogeology, environmental
engineering, hydrology and hydraulics, and review of relevant data, maps, aerials, documentation
to date, and are subject to change if and when additional information becomes available.
1.1 Summary of Opinions
It is my opinion that:
• The cap -in-place remediation scenario evaluated by HDR will not cause groundwater
standards to be met inside the compliance boundary, cause groundwater standards to be
met beyond the compliance boundary, or prevent coal ash contaminants from migrating
across the compliance boundary and into Lake Norman for the foreseeable future.
• Successful remediation of groundwater will require excavation and removal coupled with
additional measures, such as hydraulic groundwater containment.
1.2 Qualifications
My educational background, research and professional experience, and the review of documents
and models provided are the basis of my opinions. I hold the Ph.D. degree from the University of
Florida in Environmental Engineering Sciences, and I have attached a curriculum vita including
a list of peer-reviewed publications. I am the professor of Civil and Environmental Engineering
at Rice University, where I have been on faculty since 1975, and teach courses in hydrology,
1 My references to the compliance boundary mean the compliance boundary as drawn by HDR in the CSA (HDR,
2015a). My references do not imply that I believe that the compliance boundary drawn by HDR is correct.
Remediation of Soil and Groundwater Expert Opinion of
Marshall Steam Station, Terrell, NC 1 Philip B. Bedient, Ph.D., P.E.
01bob

13 May 2016
floodplain analysis and modeling, and courses in groundwater hydrology, contaminant transport,
and transport modeling. My textbook entitled "Hydrology and Floodplain Analysis" is one of the
top texts used at over 75 universities in the U.S. I have also written a textbook entitled "Ground
Water Contamination Transport and Remediation." I am currently the Herman Brown Professor
of Engineering, a Fellow of ASCE, and a Diplomat of the American Academy of Water
Resources Engineers. I am a registered professional engineer in Texas.
Groundwater Contamination and Remediation
I have been actively involved in groundwater contamination and remediation studies for many
years. I was principle investigator (PI) on a major EPA -funded study of Hill Air Force base in
the late 1990s where comparison tests for various remediation of Dense Non -Aqueous Phase
Liquids (DNAPLs) were performed. In the 1990s, I was a member of the EPA National Center
for Groundwater Research, and I held the Shell Distinguished Chair in Environmental Science
for my efforts in developing biodegradation models in the subsurface. Between 1999 and 2002, I
had the opportunity to work on the remediation of MTBE spills sites in Texas and California.
From 2000-2003, I worked on chlorinated solvent impacts and remediation strategies through a
study funded by EPA. More recently, I evaluated the impact of ethanol on groundwater and
various remediation methods on an API -funded study from 2003-2007.
I have worked on groundwater contamination and remediation litigation at more than 30 waste
sites nationwide. These sites include DOW Chemical and Vista Chemical in Louisiana; Conroe
Creosote, Brio, Texas Instruments and San Jacinto Waste Pits in Texas; Raytheon in Florida;
coal ash sites in North Carolina; BF Goodrich in California; and an Amoco site in Missouri.
My experience with groundwater contamination and remediation at military sites include Coast
Guard facility in Michigan, Eglin, Hill and Kelly Air Force Bases.
2.0 Summary of the HDR CSA and CAP Part 1 & 2
The information related in this summary is derived from the HDR Comprehensive Site
Assessment (CSA; HDR, 2015a) and Corrective Action Plan (CAP) Part 1 and 2 reports (HDR,
2015b, 2016). I have noted in this section where my interpretation of the CAP Part 1 and 2 data
differs from HDR's, and the basis for those differing interpretations are provided in my technical
opinions.
2.1 Physical Setting
Duke Energy owns and operates the Marshall Steam Station (MSS) which is located on Lake
Norman near the town of Terrell, North Carolina in Catawba County. MSS began operations as a
coal-fired generating station in 1965 (HDR, 2015b). Currently, MSS consists of four operational
coal-fired units. The first two units (Units 1 and 2) began operation in 1965 and 1966, generating
350 MW each; the remaining units (Units 3 and 4) began operation in 1969 and 1970, generating
648 MW each (HDR, 2015b). Several improvements made to these units since 1970 have
increased the electric generating capacity to 2,078 MW (HDR, 2015b). The entire MSS site is
approximately 1,446 acres in area (HDR, 2015b). Lake Norman reservoir is part of the Catawba-
Remediation of Soil and Groundwater Expert Opinion of
Marshall Steam Station, Terrell, NC 2 Philip B. Bedient, Ph.D., P.E.
®;

13 May 2016
Wateree Hydroelectric Project and is used as a source of cooling water for MSS among other
uses (HDR, 2015b).
2.2 Hydrogeology
According to the CAP Part I, the groundwater system in the natural materials (alluvium, soil,
soil/saprolite, and bedrock) at MSS is consistent with the regolith -fractured rock system and is an
unconfined, connected aquifer system (HDR, 2015b). The groundwater system is divided into
three layers to distinguish flow layers within the connected aquifer system, including the
shallow, deep, and bedrock flow layers (HDR, 2015b). HDR identifies groundwater flow from
the north and northwest portions of the MSS site to the southeast toward Lake Norman (HDR,
2015b).
2.3 Marshall Coal Ash Basin and Coal Combustion Products (CCP) Landfill
Coal combustion residual (CCR), including bottom and fly ash material, from MSS is disposed
of in the ash basin located to the north of the power plant (HDR, 2015b). The active ash basin
was constructed in 1965 by constructing an earthen dike over the confluence of Holdsclaw Creek
and Lake Norman to create a single cell (HDR 2015a, HDR 2015b). The basin covers
approximately 394 acres and is situated in historical depressions formed from Holdsclaw Creek
and its tributaries (HDR, 2015a). The earthen dike separates the ash basin from Lake Norman.
Wet ash continues to be sluiced into the basin at its southwest corner.
Dry fly ash has primarily been disposed of in six other areas at the site including the dry ash
landfill units. According to the CAP Part I (HDR, 2015b), the volumes of ash in these units are
as follows:
Unit
Estimated CCR Volume
(thousands of cubic yards)
Ash Basin
13,351
Dry Ash Landfill (Phase I)
522
Dry Ash Landfill (Phase II)
4,064
PV Structural Fill
5,410
Subgrade Fill Beneath Industrial Landfill No. 1
726
Industrial Landfill No. 1 (lined)
390
FGB Residue Landfill (lined)
569
2.4 Contamination
According to the HDR CAP Part I, corrective action at the MSS site is required to address soil
and groundwater contamination resulting from the source areas (HDR, 2015b). In the CSA, HDR
identified groundwater impacts at the MSS site; and the approximate horizontal extent of
groundwater impacts is beneath the ash basin and dry ash landfill (Phase II), east and
downgradient of the ash basin and dry ash landfill (Phase I), and southeast and downgradient of
Remediation of Soil and Groundwater Expert Opinion of
Marshall Steam Station, Terrell, NC 3 Philip B. Bedient, Ph.D., P.E.

13 May 2016
the ash basin (HDR, 2015b). HDR found groundwater impacts within both the shallow and deep
flow layers (HDR, 2015b).
According to the CAP Part I, surface water impacts were identified in the unnamed tributary that
flows to Lake Norman located downgradient of the dry ash landfill (Phase I) (HDR, 2015b).
The Site Conceptual Model (SCM) developed by HDR was used to evaluate the areal
distribution of constituents of interest (COI) within the hydrogeology of the site (HDR, 2015b).
The SCM discovered horizontal migration of COIs with groundwater flow direction at the site
(HDR, 2015b). Cobalt, iron, manganese, pH, and vanadium were the COIs with the most
widespread exceedances beneath the on-site source areas, downgradient of the source areas,
upgradient of the source areas, and in the background monitoring well locations (HDR, 2015b).
According to the CAP Part I, constituents leaching from the ash basin and dry ash landfill units
(Phase I and II) and geochemical processes taking place in groundwater and soil beneath the site
has resulted in several COIs exceeded their PPBC and/or 2L Standard, IMAC or NC DHHS HSL
(HDR, 2015b).
3.0 Efficacy of Remedial Options for Coal Ash Contaminants Evaluated by
HDR
In its CAP Part I, HDR evaluates the effects of two remedial options on groundwater
concentrations at the compliance boundary: (1) excavation of the coal ash material, and (2) the
use of a cap to reduce leaching of contaminants to groundwater. The efficacy of these two
remediation options for the COIs present in groundwater at the Marshall Station site is discussed
below.
3.1 Excavation and Removal
Excavation and removal would remove the source of the contamination (coal ash in all of the
basins) entirely in order to end the contamination of underlying groundwater. This process would
entail excavating coal ash from the site, loading it onto trucks or rail cars, and disposing of in a
secure landfill that is equipped with a proper liner and leachate collection system. This
remediation technique is underway at other contaminated coal ash sites in North Carolina. While
there is precedent for complete removal of the coal ash, additional, temporary protective
measures, such as the construction of sheet piles and coffer dams, would be necessary on this site
to prevent influx of groundwater and river water during excavation.
Ultimately, this remedial approach is feasible and the most effective remediation measure due to
permanent source removal. Even with coal ash removal, however, the current impacted
groundwater will exist as a constant source of contamination within the transmissive zones
beneath and adjacent to the site and to Lake Norman. Additional measures will be needed to
address this residual contamination at the site. Nevertheless, excavation and removal stands as
the only remediation measure that completely removes the source of contamination and, in
conjunction with other measures described below, safeguards against future contamination.
Remediation of Soil and Groundwater Expert Opinion of
Marshall Steam Station, Terrell, NC 4 Philip B. Bedient, Ph.D., P.E.

13 May 2016 %_
3.2 Cap -In-place
A cap -in-place remedy utilizes a cap of low -permeability material, including clay and/or
synthetic liners, to reduce the rate of water infiltration into the underlying coal ash. The cap may
be equipped with an underdrain system to capture even small amounts of water that infiltrates
through the cap material. In systems where contaminants are relatively fast-moving or
biodegradable, capping provides more time for the chemicals to become degraded, protecting
potential receptors downgradient.
Cap -and -treat technology is also limited, however. Where contaminants exist in thick material
that contains substantial water, continued leaching of contaminants to groundwater may occur,
even with reduced infiltration. These materials can serve as a long-term source of groundwater
impacts.
4.0 Opinions
Based on my review of the available reports and analysis of other data received to date, my
opinions are, to a reasonable scientific certainty, the following:
4.1 The remediation scenarios evaluated by HDR will not cause groundwater standards
to be met inside the compliance boundary, cause groundwater standards to be met
beyond the compliance boundary, or prevent coal ash contaminants from migrating
across the compliance boundary and into Lake Norman for the foreseeable future.
The CAP I prepared for Duke by HDR (HDR, 2015b) is not effective in addressing or mitigating
the groundwater contamination occurring at this site as a result of the leakage of coal ash
contents from coal ash disposal at the Marshall Station. In Appendix B of the CAP (HDR,
2015b), Duke acknowledges that under the cap -in-place scenario, many COIs will remain above
groundwater cleanup standards at Lake Norman compliance boundary after 100 years. Of course,
remediation measures that fail to meet groundwater standards beyond the compliance boundary
will also fail to restore groundwater to the required standards within the compliance boundary.
The excavation and removal option would perform better than the cap -in-place option, as
acknowledge by HDR in the CAP (HDR, 2015b). However, even under the excavation and
removal scenario, several COIs are all projected to remain above cleanup standards at Lake
Norman and the compliance boundary after many decades.
4.2 Successful remediation of groundwater will require excavation and removal coupled
with additional measures, such as hydraulic groundwater containment.
To eliminate ongoing migration of COIs across the compliance boundary, full excavation and
removal of the ash from the landfill and the underlying unlined coal ash pit is necessary as a first
step. The precedent for this degree of remediation is occurring currently in North Carolina
among several sites. In addition, care will need to be taken with the excavation process due to the
site's proximity to Lake Norman. This can be accomplished by means such as the construction of
sheet piles and coffer dams, or by the installation of hydraulic control wells prior to excavation.
Remediation of Soil and Groundwater Expert Opinion of
Marshall Steam Station, Terrell, NC 5 Philip B. Bedient, Ph.D., P.E.

13 May 2016
Excavation alone, however, will not prevent discharges of COIs to Lane Norman. Because of the
significant depth of the bedrock unit and the rocky composition of the lower groundwater -
bearing zones, barrier walls on the site boundaries are probably not feasible. Thus, the
implementation of additional measures will be needed in order to meet groundwater standards
under the excavation and removal approach. As a result, additional measures would need to be
implemented following coal ash removal, such as hydraulic containment to remove COI -
impacted groundwater so that COIs are maintained on Duke property. Ultimately, full excavation
and removal of the ash coupled with the suggested additional measures is the most effective
remedial approach. It is important to note that pairing such additional measures with lesser
source control strategies, such as the cap -in-place option, will still not be sufficient to meet the
groundwater standards and would be less effective than these measures coupled with source
removal.
5.0 References
Bedient, 1997. Ground Water Contamination: Transport and Remediation. Second Addition.
Bedient, Philip B.; Rifai, Hanadi S.; Newell, Charles J. 1997.
HDR, 2015a. "Comprehensive Site Assessment Report, Marshall Steam Station Ash Basin, HDR
Engineering," Inc. of the Carolinas, September, 2015.
HDR, 2015b. "Corrective Action Plan Part 1, Marshall Steam Station Ash Basin," HDR
Engineering, Inc. of the Carolinas, December 7, 2015.
HDR, 2016. "Corrective Action Plan Part 2, Marshall Steam Station Ash Basin," HDR
Engineering, Inc. of the Carolinas, March 3, 2016.
Remediation of Soil and Groundwater Expert Opinion of
Marshall Steam Station, Terrell, NC 6 Philip B. Bedient, Ph.D., P.E.