Soil remediation_20151012

DUKE
ENERGY
Harry K. Sideris
Senior Vice -President
Environmental, Health & Safety
526 South Church Street:
Mail Code ECUP
Charlotte, North Carolina 28202
704-382-4303
October 12, 2015
Mr. Tom Reeder
Assistant Secretary for the Environment
North Carolina Department of Environmental Quality
1601 Mail Service Center
Raleigh, North Carolina 27699-1601
Subject: Follow-up Regarding Soil Remediation Goals- September 15, 2015 Submittal
Dear Assistant Secretary Reader:
Thank you for your recent review of our September 15, 2015 submittal regarding Soil
Remediation Goals. As a follow-up to our discussions during our October 2"d meeting, we offer
the following comments.
Duke Energy proposes to close impoundments, pursuant to G.S. 130A-309.214(A)(1)(b), at
Asheville, Dan River, and Cliffside by (a) removing coal combustion residuals and returning the
impoundment footprints to a nonerosive and stable condition, and (b) implementing
Groundwater Corrective Action Plans submitted in accordance with § 309.211(b). Under that
section, the Groundwater Corrective Action Plans must conform to the requirements of 15A
N.C.A.C. 2L.0106. In turn, § 2L.0106(i) provides that the Department should evaluate a
corrective action plan based on the following criteria:
the extent of any violations, the extent of any threat to human health or safety,
the extent of damage or potential adverse impact to the environment, technology
available to accomplish restoration, the potential for degradation of the
contaminants in the environment, the time and costs estimated to achieve
groundwater quality restoration, and the public and economic benefits to be
derived from groundwater quality restoration.
For these three sites, corrective action will involve a combination of source control (excavation
of ash and some soil), containment (capping of remaining soils through construction of new
facilities) and/or other measures, such as groundwater remediation (yet to be determined) as
required to meet 2L .0106.
After excavation, soils left on site will be sampled and analyzed, and the analytical results will be
incorporated into the groundwater contaminant fate and transport models used to assess
alternatives for corrective action. The result will be additional information that can be used to
reassess the feasibility of a particular corrective action alternative using the criteria listed
above.

The modeling will evaluate the post -closure planned use of coal ash impoundment areas at
these three sites and will be used to determine the impacts to groundwater from the following
two scenarios:
• Proposed Methodoloqv --Removal of all ash and soil containing visible ash followed by
removal of one additional foot of soil (modeling will be conducted using analytical results
from soil sampling).
• Baseline Scenario - Removal of soil under the ash basin that may leach constituents in
excess of the protection of groundwater soil remediation goals (or natural leachable
background concentrations, whichever are less stringent) as defined in Section 4.1.1.2
of the Inactive Hazardous Sites program Guidelines for Assessment and Corrective
Action, November 2014.
The results for these modeled conditions will be evaluated to determine the appropriate
corrective action approach that will meet 2L .0106. For example, if modeling indicates that soils
left in place and capped will continue to serve as a source of contaminants that cause future
violations of 2L .0106 and that the contaminant plume will therefore threaten receptors in a way
previously unanticipated, Duke Energy will take appropriate corrective actions to protect
receptors to groundwater. For example, the corrective action approach may shift from a passive
remediation approach (such as monitored natural attenuation) to a more active approach (such
as the operation of recovery wells or installation of physical groundwater barriers).
In summary, site -specific groundwater modeling analysis will be developed to represent the
future use of the sites and will be used to analyze the potential impact of contaminated soils
remaining after closure. Based on the results from sampling and analyses and the groundwater
modeling, Duke Energy will develop corrective actions plans that will meet the requirements of
2L .0106 and that will protect receptors.
If you have comments and/or questions, please direct them to me at 704-382-4303.
Sincerely,
Harry K. ideris
Senior Vice -President
Environmental, Health & Safety