Cliffside_CoverLetterToSheliaHolman_20181115

ENERGY.
November 15, 2018
Ms. Sheila Holman
Assistant Secretary for Environment
North Carolina Department of Environmental Quality
1611 Mail Service Center
Raleigh, North Carolina 27699-1611
Paul Uraovitch
Senior Vice Presiders!
Environmental, Health & Safely
526 S. Church Steel
Mail Code: EC3XP
Charlotte, NC 28202
[phone]
Subject: Cliffside Steam Station ash basin closure options, groundwater model and community
impact analysis
Dear Ms. Holman:
Duke Energy is providing information in response to the North Carolina Department of
Environmental Quality's requests on September 13 and October 8, 2018, to submit preliminary
updates to the closure options analysis, groundwater modeling and community impact analysis
for the Cliffside Steam Station at Rogers Energy Complex. These studies represent a key
portion of the work the company has performed to develop closure plans that balance a variety
of considerations.
Duke Energy is committed to closing ash basins in ways that are safe, timely, environmentally
sound, and based on thorough science and engineering. In addition, effective closure plans are
site -specific and must ensure ash is managed in ways that continue to protect public health,
safety and the environment. Importantly, the planning process also considers how closure
choices may affect neighbors and communities.
After considering a number of potential closure options at Cliffside, three options were advanced
for detailed analysis: closure -in -place for both basins, closure -by -removal to an on -site landfill
for both basins and a hybrid closure (evaluated for the active basin only.)
Based on a comprehensive assessment, Duke Energy will recommend at a later date either
closure -in -place or a hybrid closure plan to safely close the Cliffside active ash basin. For the
inactive basin, the company recommends closure -in -place. We look forward to input from
regulators and interested stakeholders as we continue to evaluate safe closure methods in a
manner that protect people and the environment, while also minimizing disruption to
communities and managing cost.
North Carolina As a National Leader
To help ensure that the work done in North Carolina balances various considerations and
incorporates interdisciplinary perspectives, the company created the National Ash Management
Advisory Board (NAMAB) in 2014. This group of well -recognized experts in environmental
engineering, waste remediation, toxicology and other fields continues to provide ongoing
technical input and vet the various choices and tradeoffs inherent to any closure plan.
As previously stated, the enclosed documents represent key elements among the extensive
science and engineering being conducted by dedicated teams at Duke Energy and outside

experts, with ongoing input from NAMAB, to identify safe and smart basin closure plans for
remaining sites in North Carolina.
Groundwater Modeling
As multiple sources have validated, ash basins have not affected neighbors' drinking water
wells near the Cliffside Steam Station. For communities concerned that nearby well water could
be affected in the future, state lawmakers in 2016 passed legislation requiring the company to
proactively provide permanent drinking water sources. The company has connected eligible
neighbors within a half -mile of the Cliffside basins to municipal water supplies or provided them
with advanced, whole -home filtration systems, even though evidence demonstrates that ash
basins are not impacting them, and most neighbors' well water already met the appropriate
performance standards for the filter systems.
In addition to advanced planning for safe drinking water, the N.C. Coal Ash Management Act
(CAMA) outlines an elaborate process to monitor and study groundwater near ash basins. This
involves thousands of monitoring wells across the state and using those real -world data points
to develop site -specific models that seek to predict how groundwater will respond to various
closure scenarios. This process also involves several iterations of extensive groundwater
studies and developing proposed corrective action steps that will work in tandem with basin
closure as necessary to address groundwater impacts.
Based on extensive study, the company understands that groundwater at Cliffside moves slowly
and that coal ash impacts are very localized near the ash basin and generally on plant property.
In any closure scenario, the most effective step the company can take to improve groundwater
is to safely remove the free water from the ash basin. When predicting future groundwater
response at Cliffside, the models demonstrate that:
For the active ash basin, the groundwater response is very similar at the designated
downstream location for the first 100 years. After that point, the simulations show more
rapid groundwater response for the excavation scenario, while the hybrid and capping
scenarios show a slower response.
In most cases, current boron levels in the inactive ash basin are below the state
groundwater standard.
The simulations indicate there will continue to be no impact to drinking water wells.
Groundwater impacts will continue to be evaluated as the updated modeling expands to other
parameters.
The models do not include the effects of any additional groundwater remediation steps the
company may take in the future. As part of a separate state -directed process, the company will
submit corrective action plans that propose steps that can be taken where groundwater
necessitates additional or more timely improvement. In particular, the company will pursue
groundwater remedial actions where needed with a focus on any surface water or offsite
property impacts.

Community Impact Analysis
In addition to relying on strong science and engineering, the company felt it important to
consider various stakeholder interests and community impacts when developing its
recommended ash basin closure plans. In addition to its own research, which is included in the
comprehensive options analysis, the company relied on an outside consulting firm, Exponent, to
study the potential community impacts of various closure scenarios. Key take-aways include:
• All closure options evaluated would be protective of human and ecological health.
• All closure options evaluated would create similar levels of disturbance to the local
community, but the disruption in excavation scenarios (noise and traffic) would be
extended because of the time necessary to complete construction.
• Cap -in -place closure would cause a net loss in ecological services (protection of
blodiversity and natural beauty), because a grass cap is less valuable habitat than open
fields, wetlands or forested areas. All other closure options evaluated would create a net
gain in ecological services. Any net loss in ecological services resulting from closure -in -
place can be offset by reforestation of land parcels.
The community impact analysis does not compare greenhouse gas emissions from onsite and
offsite trucking activity; therefore, a supplemental analysis will be provided comparing the
impact of various closure options on greenhouse gases and other air emissions.
The results of the community impact analysis vary by site, but in all cases cap -in -place closure
may be performed without adversely impacting the community. In some cases, reforestation of
land parcels may be advisable to offset any net habitat losses.
The conclusions in the community impact analysis are subject to revision if new landfill space
must be created to accommodate production ash. In such circumstances, excavation options
would score tower in the community impact analysis.
Options Analysis
The company's options analysis considers the many aspects and tradeoffs related to basin
closure including environmental protection, schedule and the company's own analysis of
community impacts. In addition, as a regulated utility, Duke Energy is obligated to evaluate the
cost-effectiveness of the closure options. The company developed a relative weighting and
scoring system with input from the NAMAB that was used to evaluate and score various closure
alternatives.
At Cliffside, the Unit 1-4 ash basin already has been excavated, with that ash transported to the
on -site landfill and the footprint repurposed for other plant needs. The options analysis, then,
focused on plans for the active ash basin and the Unit 5 inactive_ basin. For Cliffside, key take-
aways from the options analysis include:
• Closure -in -place is the lowest cost option for both basins. The excavation option is twice
as expensive as capping for both basins combined.
3

No ash transportation occurs on or across public roads for any of the options. All work is
onsite; however, landfill -related work and ash placement for the excavation option would
be readily visible from Duke Power Road.
Closure -in -place can be completed faster at both basins than the other options. Closure -
in -place options and the active basin hybrid option can be completed before the CAMA
deadline of 2029. Full excavation of the inactive basin also could be completed before
the deadline, but excavation of the active basin is likely to exceed the deadline.
The company's recommended closure approach across its North Carolina sites reflects a
science -based combination of excavating, capping in place and recycling ash for concrete and
other beneficial purposes. Duke Energy remains committed to safely closing ash basins and
welcomes input from DEQ and the public to best balance these various tradeoffs.
Sincerel ,
Paul Draovitch
Senior Vice President
Environmental, Health & Safety
cc: Jim Wells, Duke Energy
Dave Renner, Duke Energy
Randy Hart, Duke Energy
Ed Mussler, DWM
Jon Risgaard, DW R
Andrew Brooks, DEMLR
Bill Lane, NCDEQ General Counsel