Rob Powell Supplemental Expert Report (Mayo and Roxboro)

Supplemental Expert Report
of
Robert L. Powell Ph.D., P.E.
In the matter of
State of North Carolina ex. rel. North
Carolina Department of
Environmental Quality vs.
Duke Energy Progress, LLC.
Prepared for:
Hunton & Williams, LLP
Charlotte, NC
Prepared by:
Ramboll-Environ US Corporation
Tampa, Florida
Date:
September 21, 2016
Project Number:
25-39485A
ENVIRON

Contents
1 Introduction
2 Qualifications and Experience
3 Materials Considered
4 SupplemtalOpinions
5 Signature
Page
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1 Introduction
I have been retained by Hunton & Williams, LLP on behalf of its client, Duke Energy Progress,
LLC ("Duke Energy") to conduct an independent evaluation and provide certain expert opinions
in response to a lawsuit filed by the state of North Carolina in the matter of State of North
Carolina ex. rel. North Carolina Department of Environmental Quality and Roanoke River Basin
Association (plaintiffs) vs. Duke Energy Progress, LLC. The opinions I have formed in this
matter were presented in two expert reports I have previously authored related to the Mayo and
Roxboro Steam Generating Stations. These opinions generally related to the current ground
water conditions on these plant sites and the potential efficacy of Duke's alternatives for the
closure of the former and active ash management basins pursuant to the requirements of the
Coal Ash Management Act. I
Since preparing my original Expert Reports, supplemental reports were authored by Mark A.
Hutson, PG, 2 in which he discussed the experience of two utilities in South Carolina related to
the closure of ash basins at the SCE&G Wateree and the Santee Cooper Grainger generating
stations. Mr. Hutson uses these SC utility experiences to argue in his Supplemental Reports
and deposition testimony that removal of the ash would potentially result in a relatively rapid
improvement in ground water quality at the Duke Energy's Mayo and Roxboro plants. The
purpose of my Supplemental Report is to respond to Mr. Hutson's presentation and conclusions
in this regard. I also understand that another expert witness proffered by the Southern
Environmental Law center, Dr. Robert Parette, is relying upon his experience analyzing
subsurface conditions at Dominion's Chesapeake Energy Center adjacent to the Elizabeth River
in Chesapeake, Virginia. This Supplemental report also contrasts the site geology of the
Chesapeake Energy Center with that of the Duke Energy plants.
My qualifications as an expert in this case are provided in Section 2 of this report. The materials
I have relied on in formulating my opinions presented herein are identified in Section 3. The
detailed explanation of my opinions are presented in Section 4.
I am compensated by my employer, Ramboll-Environ US Corporation (Ram boll -ENVIRON), for
my services and expenses on this matter at my normal hourly compensation rate. Ramboll-
ENVIRON bills Duke Energy at a rate of $300/hour for these services.
I have also authored a report for another Duke subsidiary on the same topics related to the Cliffside Steam
Generating Station. The geology of the Cliffside Generating Station, like that of the Roxboro and Mayo sites, is not
comparable to that of the coastal plain on which the Wateree, Grainger and Chesapeake Energy Center
generating stations sit.
2 Mr. Hutson is a geologist retained by the Southern Environmental Law Center to opine on certain issues related to
ground water conditions at Duke's Mayo and Roxboro plants
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2 Qualifications and Experience
I am a Principal of Ramboll-Environ US Corporation ('Ramboll-Environ") in Tampa, Florida.
Ramboll-Environ (formerly ENVIRON International Corporation ("ENVIRON')) is an international
consulting firm that provides scientific, engineering and strategic risk management services to
clients in the public and private sectors. ENVIRON was formed in 1982, and in December 2014,
merged with Ramboll. The combined Ramboll-Environ has nearly 300 offices and over 12,000
employees worldwide.
I am a practicing professional engineer,3 hydrologist and hydrogeologist. I received a Ph.D. in
Civil Engineering (Groundwater Hydrology) in 1983. 1 received an M.S. in Civil Engineering
(Water Resources) in 1977. 1 received a B.S. in Civil Engineering (Environmental Engineering)
in 1973. All my degrees were received from the University of Maryland, College Park.
I have approximately 40 years of experience as a practicing consultant in the fields of
environmental engineering, surface and ground water hydrology, hazardous waste
management, contaminated site investigation/remediation, risk assessment, and environmental
risk management. This experience includes professional consulting services at many of the
largest solid waste management facilities throughout the United States that are regulated under
federal and state environmental statutes. My recent work as an expert included consulting
services at two large coal ash management facilities in the state of Maryland, focusing on issues
of the impacts to underlying and adjoining ground water/surface water systems and the efficacy
of closure alternatives that had been implemented at the sites. I have also conducted
environmental investigations, and evaluated corrective action requirements at numerous
industrial and commercial facilities that generate, manage and store solid/hazardous wastes
and other regulated materials for federal, state, and private clients. These have included
facilities that have undergone closure under RCRA, TSCA, CERCLA, and related state
regulatory programs. One of these facilities was the Safety-Kleen hazardous waste landfill in
Pinewood SC, where I served as a senior hydrogeologist to investigate and characterize
subsurface hydrogeological conditions in support of the facility's RCRA Part B permit
application. The Safety-Kleen facility is located about 10 miles east (downstream) of the SCE&G
Wateree station. I have previously been qualified as an expert and testified on numerous
occasions in United States federal (District and Bankruptcy) courts and state courts in the fields
of ground water hydrology, environmental investigations and remediation planning,
environmental risk management, and cost allocation/National Contingency Plan (NCP)
consistency under CERCLA regulations.
3 My currently active PE license (No. 64379) is in the state of Florida, where I currently reside and work.
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3 Materials Considered
The opinions set forth in this report are based on my approximately 40 years of experience in
consulting engineering, as well as my formal academic training as an environmental engineer
and hydrologist/hydrogeologist. In forming my opinions, I considered various documents that
were identified in my prior Expert Reports and were provided to me at my request by counsel. I
also reviewed and considered the various reports, opinions and deposition testimony of the
opposing experts in this matter (Mr. Mark Hutson and Dr. Robert Parette).
In preparing this Supplemental Expert Report I have obtained copies of certain reports that
provide the ground water monitoring record for the SCE&G Wateree Station including the
following:
Wateree Station Semi -Annual Status Report, July -December 2012; SCE&G; January, 2013.
Wateree Station Semi -Annual Status Report, January — June 2013; SCE&G; July 2013.
Wateree Station Semi -Annual Status Report, July — December 2013; SCE&G; January 2014.
Wateree Station Semi -Annual Status Report, January — June 2016; SCE&G; July 2016; which
includes the following as an attachment:
Semi -Annual Water Quality Monitoring Report: April 2016 Monitoring; SCE&G, Wateree Station,
Eastover, South Carolina; Nautilus Geologic Consulting, PLLC; May 22, 2016
1 also reviewed certain historic aerial photographs of the SCE&G Wateree station that are
available on the historic archives of Google Earth that show the progression of closure activities
on the main ash storage pond.
I also obtained certain information (discussed in Section 4 below) during a conference call with
staff at SCE&G [Mr. Tom Effinger (Director, Environmental Services) and Mr. Jean-Claude
Younan (Supervisor, Environmental Services)] related to hydrogeological conditions at the
Wateree station and SCE&G's activities and history for the closure of their onsite ash
management pond.
I have not yet obtained any specific information related to the Santee Cooper Grainer station
property and closure activities (or Dominion's Chesapeake Energy Center) beyond general
information available on the internet, and historic photos available on Google Earth, but
continue to pursue such information through counsel.
I reserve the right to amend or supplement my opinions if additional information becomes
available.
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4 Supplemental Opinions
4.1 Opinion 1
The SCE&G Wateree station is located in the coastal plain region of central SC, on a property
bordering the Wateree River. The Wateree station property is underlain by a thick sequence of
marine and alluvial (water -borne) sediments. The shallow -most of these sediments included
alluvial (water -borne) sand/gravel and clay deposits. These shallow sand and gravel deposits
were historically mined, creating a large shallow impoundment that was subsequently modified
by SCE&G to serve as an ash management pond. This pond is located on a low terrace deposit
immediately adjoining the river. Underlying these sand and gravel deposits is a clay unit.
SCE&G first began some limited removal of ash from the pond for recycling/beneficial reuse
circa 1999. Ash continued to be sluiced from the power plant into the pond, however, until as
late as 2016. More active removal of ash along the pond's eastern boundary began in 2011-
2012, when a wide trench was excavated thru the ash into native soil along the earthen berm
that defines the boundary of the pond nearest the river. The trench was subsequently actively
pumped to remove accumulated water, eventually creating a dry pond bottom. Upon completion
of dewatering, an approximately 700 -foot section of the inside the berm was lined with a
synthetic material, keyed into the underlying clay, to limit future seepage of water from the pond
towards the river.
Immediately adjoining and outside the lined section of the berm nearer the river is a monitoring
well (MW -11), water from which has historically exhibited elevated concentrations of arsenic in
excess of 1,000 ug/L (see Semi -Annual Water Quality Monitoring Report, April 2016
Monitoring). This well was reported to me by SCE&G to be shallow, and screened in the water
table zone. When the ash pond was pumped to dewater the excavated trench inside the berm,
the water level in MW -11 was reported to decline from historic norms, indicating a hydrogeologic
connection existed between the pond and the adjoining flood plain sediments.
Pumping/dewatering of the pond, therefore, likely created a reversal of the normal direction of
ground water flow such that ground water would then flow from the river towards the pond to
some degree. This reversal of flow during pumping would have likely caused some flushing of
constituents of interest (Cols) such as arsenic from the water table sediments outside the pond,
as SCE&G's testing of the river water quality indicate arsenic levels in the river are low.
The water quality history of MW -11 indicates a demonstrable decline in the concentration of
arsenic beginning in 2013, approximately a year or more after SCE&G excavated the ash along
the berm and began active dewatering of the ash pond in this area. This decline was likely
primarily the result of the dewatering activity, given how rapidly it occurred, the relatively
permeable sand and gravel sediments reported to be in this area, the response (decline) in the
water table outside the pond caused by the pumping, and the fact that the majority of the pond
remain full of ash throughout this period and would be a continuing source of Cols to underlying
ground water. It is highly unlikely that the removal of the ash alone could have caused this
relatively rapid decline.
The ash deposits in this Wateree station pond are relatively shallow as compared to the ash
management ponds at the Mayo and Roxboro stations. Excavation/dewatering of the ash along
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the downstream portions of the Duke Energy ponds in the manner as was done at the Wateree
station is likely not feasible, certainly not within the same timeframes as occurred at the
Wateree station. In addition, the soils and hydrogeology in the central South Carolina coastal
plain near the Wateree station are geochemically and hydrologically quite different from the soils
and saprolite formed by the in-place weathering of the fractured metamorphic rocks found
beneath Duke Energy's Mayo and Roxboro plant in the Piedmont region of north -central NC. It
is unlikely, therefore, that the apparent history of relatively rapid water quality improvement in
the area bordering the ash pond at the Wateree station would be an applicable model of
expectations for water quality changes at Mayo or Roxboro if those stations' ponds were
eventually closed by excavation.
4.2 Opinion 2
The Santee Cooper Grainger power plant is located in eastern South Carolina, on the east side
of Conway, SC. The plant operated for approximately 50 years, until 2012, and is currently
undergoing demolition and closure. The Grainger Station is on the far -eastern coastal plain,
approximately 14 miles inland from the Atlantic Ocean. It is bounded by Highway 501 to the
south and the W accama River to the east. Based on its location on the far eastern coastal plain
and its proximity to the river the Grainger Station property is likely underlain by a thick sequence
of sediments of marine and alluvial (water -borne) origin, the shallow -most of which
communicate (drain) to a greater or lesser degree into the river by seepage through the bottom
sediments. The nature and origin of these soils and the hydrogeological conditions beneath the
Grainger Station property, are quite different than those found beneath the Mayo and Roxboro
Station properties, which are located in the Piedmont region of north -central North Carolina.
I have not yet obtained any information on the specific activities on the Grainger Station related
to the closure of the ash management ponds, such as where and how much ash has been
removed and any associated dewatering activities that may have been employed.4 Based on
what is known about the property and can be reasonably inferred about underlying conditions,
however, the historic water quality trends reportedly observed at the Grainer station as cited by
Mr. Hutson, specifically related to the rate of change in ground water quality at individual
monitoring wells which he associates with ash removal activities, cannot be assumed to be
applicable to the future conditions at the Mayo or Roxboro stations.
4.3 Opinion 3
Like the Santee Cooper Grainger station, Dominion's Chesapeake Energy Center is located
near the Atlantic coast of southeastern Virginia, in an area underlain by marine and alluvial
sedimentary deposits. The hydrogeology of this area and the geochemistry of the underlying
soils and ground water systems, are quite different from those found at the Duke Energy plants
in north central North Carolina. As a result, any "lessons" or observations Dr. Parette cites from
his experiences at the Dominion plant as it may relate to the degree of ground water impacts
and the rapidity of ground water quality changes upon closure of ash management facilities can-
not be assumed to be applicable to the future closure of the ash management ponds at the
Duke Energy facilities.
4 1 note that no such information was cited by Mr. Hutson in his report.
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5 Signature
The opinions in this expert report are based on my education and training as a
civil/environmental engineer and hydrologist/hydrogeologist, my more than 40 years of
experience in environmental consulting, and the materials listed in Section 3 above. I
may revise these opinions as additional information, documents, testimony, or discovery
responses become available.
Robert L. Powell, Ph.D., P.E.
September 21, 2016
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