NC0004961_Follow up to 7/24/15 Joint Meeting_20150808

DUKE Harry K. Sideris
Senior Vice President
ENERGY. Environmental, Health&Safety
526 S. Church Street
Mail Code:EC3XF
Charlotte, NC 28202
[phone]
August 4, 2015
James D. Giattina
Director, Water Protection Division
U.S. Environmental Protection Agency
Region IV
Atlanta Federal Center RECEIVED/DENR/DWR
61 Forsyth Street
Atlanta, GA 30303-8960 AUG - 8 2015
dvater Quality
Subject: Follow up to July 24, 2015 Joint Meeting Permitting Section
Dear Jim:
This letter follows up on our July 24, 2015 meeting regarding NPDES permitting at Duke
Energy's North Carolina ash basins. As we discussed, resolution of these permit issues is both
an important step in the safe maintenance and operation of basins that no longer receive
wastewater and a time-critical element in meeting deadlines under North Carolina law for
closure of Duke Energy's ash basins. I appreciate your meeting with us last week and EPA's
willingness to continue the dialogue as we work to resolve outstanding issues on the permit for
Riverbend and other high priority permits. We expect that resolution of the technical questions
that arose on these initial permits will help streamline issuance of the remainder of the pending
permits and enable basin dewatering and closure to proceed expeditiously. In that regard, this
letter lays out the issues we discussed and summarizes Duke Energy's proposed approaches to
resolve the major outstanding issues.
Decanting
Decanting free-standing water from ash basins serves two critical purposes in Duke Energy's
plans for ash basin management. It is an important step in the safe operation and maintenance
of ash basins that no longer receive new ash, reducing the risk of unplanned discharges
(including seeps) and providing better and safer access for inspections, repairs and
maintenance. Decanting is also a necessary first step in dewatering and excavating ash from
the basins. As a result of our meeting, it is our understanding that EPA and NC DENR are open
to the idea of decanting under existing NPDES permits once NC DENR and Duke Energy have
provided an appropriate framework for doing so (e.g., consistent with the terms of the existing
permits, based on data regarding distribution of constituents in the ash basin water column and
sufficiently frequent monitoring, etc.). NC DENR will develop a proposed approach to allow
decanting to proceed expeditiously and provide that plan to EPA for its consideration. Duke
Energy is committed to implementation of a plan for performing the decanting that assures it will
be conducted in compliance with permit limits and under specified conditions.

With regard to decanting at the Riverbend station, the flow of free-standing water during
decanting (at a maximum outflow of 1.45 MGD)will be small compared to flows when the
station was operating (with average flows of around 5.0 MGD in 2009). We have previously
provided analytic data to NC DENR and EPA demonstrating that the free water in the basin is
well within permit limits, and that data is consistent throughout the water column. There is no
evidence of stratification in the free water at lower levels. Our decant plan includes controls on
how the decanting would be conducted and additional monitoring to assure compliance with
permit limits, including:
• flows less than average historical discharge rates;
• drawdown limited to 1 foot per 7 days to ensure structural stability;
• use of a floating pump station with free water skimmed from basin surface using an
adjustable weir;
• daily monitoring of flow;
• real time monitoring of Total Suspended Solids (TSS) with auto pump shut-off if TSS
concentration (15 min. average) exceeds half the maximum daily TSS limit;
• real time pH monitoring with auto shut-off if 15 minute running average pH falls
below 6.1 standard units or rises above 8.9 standard units;
• drawdown to no less than three feet above the ash; and
• notice to Agencies and ability to monitor/verify.
Duke Energy would not object to NC DENR's use of its authority under North Carolina
Administrative Code Chapter 15A, section 26.0505 to make this monitoring mandatory and
enforceable. We believe this comprehensive approach allows the essential dewatering work to
proceed under the terms of the existing NPDES permits, while providing all necessary
safeguards to assure that dewatering is done appropriately.
Duke Energy prefers an approach such as the one discussed in our meeting that allows it to
begin decanting free water expeditiously and in advance of the new Riverbend permit issuance.
This is particularly important since the permit likely will have to be re-noticed as modifications
are made to the permit as further discussed below.
Seep Monitoring
We appreciated the opportunity to lay out our current thinking on seep management and how to
address various types of engineered and non-engineered seeps. Specifically, Duke Energy's
plan provides for seep categorization into five categories. Categories 1 (engineered seeps) and
2 (non-engineered seeps) address seeps that lead to surface water. For seeps in either of
these categories, Duke Energy will either (a) develop measures to eliminate, capture and/or
redirect seep flow so it does not discharge or(b) incorporate the seep into the NPDES permit
and comply with applicable limits. Categories 3, 4, and 5 would not require incorporation into
NPDES wastewater permits. (Categories 3 and 4 involve seeps that do not discharge to surface
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waters; these will be inspected, monitored and sampled. Category 5 includes storm water,
groundwater springs or other conveyances that do not contain contact water which would be
addressed under applicable storm water permits.)
During our meeting, we discussed EPA's comment on the draft permit questioning the adequacy
of bi-annual monitoring of seeps covered under outfall 010. We understand that EPA's concern
is based in part on the lack of historical data about seep discharges on which to base a
conclusion that the seeps are consistent between monitoring events. All parties expressed
openness to the idea of a more intensive sampling regime in the first year of the permit,with
less frequent monitoring after the first twelve months. Duke proposes to change the frequency
of monitoring to monthly during the first twelve months. After twelve months, monitoring
frequency will be reduced to semi-annual unless the monthly monitoring data indicates that the
reasonable potential analysis for seeps was based on incorrect assumptions.
TBELs
At the meeting, Duke Energy expressed concern about TBELs for seeps at Riverbend (and
other sites without FGD scrubbers) derived from waste streams at sites with FGD scrubbers.
Based on our discussion and exchange of views, we propose the following approach for these
sites:
• Until the new ELGs are finalized, TBELs for seeps at sites without FGD scrubbers
will not include total arsenic, total selenium, or nitrate/nitrite. They will include oil &
grease (O&G) and total suspended solids (TSS).
• These TBELs will be based on limits for combustion residual leachate proposed in
the ELG rule and the low volume limits in the current ELGs. These limits are as
follows:
Monthly Avg. (mg/L) Daily Max. (mg/L)
O&G 15 20
TSS 30 100
Applying this approach to the draft permit for Riverbend, which did not have an FGD scrubber,
the following changes are needed:
• Outfall 002:The limits for arsenic, selenium and nitrate/nitrate limits would be removed.
This includes the limits effective upon the effective date of the permit and the limits
effective 4.5 years from the effective date of the permit. The current TSS and O&G limits
(which are more restrictive than those in the new ELGs) would remain.
• Outfall 002 (dewatering): The limits for arsenic, selenium and nitrate/nitrate limits would
be removed. The current TSS and O&G limits would remain.
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• Outfall 010 (combined seep): The limits for arsenic, selenium and nitrate/nitrate limits
would be removed. Limits for O&G would be added (monthly average: 15 mg/L; daily
max: 20 mg/L). The TSS limits would remain.
• Table 1 Seep Monitoring Parameters and Screening Values: The screening value for
nitrate/nitrite would be removed. The screening values for arsenic and selenium would
be revised to be consistent with other screening values (i.e., 10 times the highest
baseline seep concentration).
• Outfall 011: The monitoring requirements for arsenic, selenium and nitrate/nitrite
would be removed. The current TSS and O&G limits would remain.
• The modified proposed Riverbend permit will need to republished for public notice.
Wastewater/Waters of the United States
As we discussed, recent work performed by the US Army Corps of Engineers has raised the
possibility that seeps treated as wastewater flows by NC DENR and EPA would also be
designated as jurisdictional waters of the United States by the COE. We think that there was
general agreement among Duke Energy, EPA, and NC DENR, that surface water features
created by wastewater migrating from an ash basin should be treated as part of the treatment
system, rather than as waters of the United States. Surface water features that are not created
by wastewater migrating from an ash basin should be treated as waters of the United States
and protected from point source discharges of pollutants. We agreed that the best course of
action would be to schedule a site visit involving the COE, NC DENR, and EPA, as a first step in
reaching a coordinated approach and consistent classification of these features. We appreciate
NC DENR's and EPA's willingness to participate in a Riverbend site visit, along with the COE, to
clarify the status of seeps that create jurisdictional features that are hydrogeologically connected
to the treatment system. We are in touch with your staff and DENR and have scheduled the
Riverbend site visit and hope that work on this issue can be completed within the next few
weeks.
Again, thank you and your staff for meeting with us. I found our exchange very productive and
look forward to our next meeting. I will be reaching out again soon to schedule additional
meetings as we move ahead with this plan.
Sincerely,
Harry Sideris
Duke Energy, Senior Vice President
Environmental, Health & Safety
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cc: Tom Reeder, Assistant Secretary for the Environment, NC DENR
Jay Zimmerman, Water Resources Director, NC DENR
Jeff Poupart, Water Quality Section Permitting Chief, NC DENR
Sam Hayes, General Counsel, NC DENR
Denisse Diaz, Chief, Clean Water Enforcement Branch,Water Protection
Division, EPA R.4
Mita Ghosh, Acting Deputy Director,Water Protection Division, EPA R4
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