NC0001422_Decanting Wastewater_20140916

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O' UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
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SEP 1 6 2014 \cr\4,4.1
14411
Mr. Jeff Poupart
Chief, Permitting Section
Division of Water Quality S4� 2.2 2014
North Carolina Department of Environment
and Natural Resources f'f
1611 Mail Service Center
Raleigh, North Carolina 27699-1611
Subject: Letter Dated August 28, 2014 to Duke Energy Regarding Decanting of Wastewater
Dear Mr. Poupart:
This letter is to recommend that you withdraw the above-referenced letter(enclosed) and provide
additional information about the potential effluent characteristics of the decanted wastewater. The U.S.
Environmental Protection Agency is concerned that the August 28, 2014, letter will create uncertainty
that could result in Duke Energy discharging wastewater with pollutants not authorized in a National
Pollutant Discharge Elimination System (NPDES) permit.
The letter attempted to clarify for Duke Energy that it may proceed to "decant all the wastewater in the
ash pond above the ash level"at each of 14 ash ponds under currently applicable NPDES permits. It
prohibits Duke Energy from removing wastewater by dredging, trench excavation or other mechanical
movement of the ash. The letter requests Duke to submit chemical characterization of the interstitial ash
water and predicted volume of wastewater that would be generated by mechanical dewatering. The letter
gives Duke no deadline by which to submit this information.
The extent to which the pond can be drawn down through "decanting," as opposed to mechanical
dewatering, is not clear in the letter. Rather than clarifying the issue, the letter creates uncertainty as to
whether or not Duke is, or is not, authorized to discharge through the decanting process almost all liquid
in the ash ponds, including interstitial ash water. It is also not clear whether Duke Energy, through this
letter, is now newly authorized to discharge additional pollutants or higher pollutant concentrations that
may be present due to any changes in effluent quality while the ponds are drawn down to the ash level.
The letter indicates that the discharge of"supernatant" shall be monitored in accordance with the
NPDES permit. However, the applicable permits only require monitoring for a limited number of
pollutants once every six months. As a result, Duke Energy could draw the ponds down completely
without taking a single sample to assess effluent quality, permit compliance, or water quality impact.
Based on the EPA's review of Duke Energy's initial applications and permit documents, it does not
appear that they requested authorization to conduct large-scale"decanting"or drawdown processes. It
does not appear that Duke Energy disclosed information or data about the effluent characteristics and
average flows of the decanted wastewater as required by 40 Code of Federal Regulations (CFR)
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122.21(g). Nor does it appear that the North Carolina Department of Environment and Natural
Resources contemplated large-scale decanting when issuing each of the 14 Duke Energy permits.
The characterization of effluent quality and quantity in the permit applications appear to have been
based on normal (gravity-based or passive) discharges of wastewater from the surface of the ponds after
full settling has occurred. It is possible, however, that higher concentrations of pollutants may be present
at deeper levels in the pond which will be discharged in the decanted wastewater. Further, the drawdown
of wastewater may involve a much higher discharge rate than contemplated at the time the permits were
issued. The letter also relates to 14 separate facilities, which have different receiving stream conditions,
such as minimum flows and existing water quality which could affect a revised reasonable potential
analysis.
There was no information in the letter showing that any analysis of potential changes to effluent quality
or quantity has been undertaken, nor any evaluation of the impact that such changes might have on a
revised reasonable potential analysis for the additional discharge. Should this information already be
available,please submit it for our evaluation.
Without additional information, it is not possible to determine whether or not a formal permit
modification would be necessary to authorize the discharge of changed effluent quality or volume that
may occur during the decanting process at these 14 facilities. However, it is likely that at a minimum,
significant additional monitoring(if not additional effluent limitations) during the decanting process
would be warranted to ensure compliance with existing effluent limits and water quality standards.
Without submittal of additional information by Duke Energy and subsequent revised reasonable
potential analyses by DENR, made available to the EPA and the general public, discharges of additional
decanted wastewater and additional pollutants will not qualify for NPDES permit shield protections
under Section 402(k) of the Clean Water Act.
The EPA therefore requests that DENR withdraw the letter and obtain additional data for each facility at
which Duke Energy plans to decant or drawdown any and all additional wastewater to the ash level.
If you have not already done so,the EPA requests that you require Duke Energy to provide the
following information to DENR for each of the 14 facilities referenced in the letter:
- data characterizing the effluent quality, of the decanted wastewater to the ash level;
- anticipated weekly average and maximum daily wastewater flow rates during drawdown;
- pollutant concentrations in ash ponds at various depths between the base and surface of the
ponds for all pollutants known or believed to be present in the discharge of decanted
wastewater to the ash level;
- data showing background pollutant concentrations in receiving streams for all pollutants
known or believed to be present in the discharge of the decanted wastewater;
- low(7Q10) stream flow in each receiving waterbody; and
- additional information about how it will be ensured that only decanted wastewater and not
wastewater resulting from dredging the ash, excavating the trenches, or any other mechanical
movement of the ash will be discharged.
DENR should use the additional information to conduct revised reasonable potential analyses for each of
the 14 facilities to inform decisions regarding the need for a permit modification and the potential need
for additional monitoring requirements and/or water quality based effluent limits.

The EPA requests that you provide us with this data and information for our review, as well as revised
reasonable potential analyses. This will enable us to appropriately determine together with DENR
whether or not formal permit modifications will be required to authorize Duke Energy to discharge
decanted wastewater from these 14 facilities.
The EPA notes that any permit modifications should include additional technology-based effluent
limitations on a case-by-case basis based on best professional judgment as required section by § 402(a)
of the Clean Water Act, 40 CFR § 122.44(a), § 123.25, and § 125.3. In particular any additional
technology-based effluent limitations should address pollutants discharged from the ash ponds that are
not included in effluent guidelines for the steam electric power generating industry in 40 CFR Part 423.
In subsequent discussions with representatives of DENR, it appears that one of the worthy goals of this
letter was to expedite closure of some ash ponds by addressing Duke Energy's need to remove
wastewater from the pond. We recommend that you consider alternative enforceable approaches, in
addition to potential permit modifications, that will achieve this purpose while ensuring protection of
water quality during the decanting process.
The EPA looks forward to working together with DENR to discuss our requests and recommendations
to ensure that any discharges of wastewater from the decanting or dewatering process be appropriately
authorized.
Sincerely
Mark J. Nuhfer, Chief
Municipal and Industrial NPDES Section
Enclosure
cc: Mr. Mark McIntire
Duke Energy
RECEIVED/DENR/DWR
SEP 22 2014
Water Quality
Permitting Section

(S DUKE
ENERGY. RECEIVED/DENR/DAT
OCT OP. /0t4
Water Quality
September 30, 2014 Permitting Sect'
Via email and UPS
Mr. Jeff Poupart
Water Quality Permitting Section Chief
N.C. Department of Environment and Natural Resources
1611 Mail Service Center
Raleigh, NC 27699-1611
Re: Withdrawal of August 28, 2014 Operating Condition Clarification Letter
Dear Mr. Poupart:
This is to acknowledge receipt of your letter of September 19, 2014, withdrawing
the previous letter of clarification of August 28, 2014.
The letter of August 28, 2014, arose out of several shared concerns between
Duke Energy and DENR. These included the efficient and safe operation of ash basins,
particularly those that were inactive, and an understanding of how Duke Energy will
move towards the closure of ash basins at former coal-fired plants currently undergoing
decommissioning.
In order to excavate ash from the ash basins (which Duke Energy has now been
directed to do by an act of the North Carolina General Assembly), and to expedite
necessary inspections and repairs, Duke Energy must first remove free-standing water.
Given that this water had already undergone treatment, DENR clarified that the
Company's NPDES permits authorized the decanting of free-standing water above the
ash level so long as the removal did not cause exceedances of permit limits. Duke
Energy notes that the amount of free-standing water that would be removed from these
inactive basins would be well within the amount of treated water that the NPDES
permits allow to be discharged on a daily basis.
Before issuing the letter of August 28, 2014, DENR indicated on a number of
occasions that the movement of free-standing water from inactive basins was
permissible under the NPDES permits (so long as effluent limits were met), an
interpretation with which Duke Energy agreed. The letter of August 28, 2014, thus did
not constitute a departure from prior DENR practice nor was it a "new" interpretation,
and we understood that it was simply a written confirmation of what DENR believed its
permits allowed.
Your letter of September 19, 2014, alters this position. Based upon the letter that
we received from Mr. Mark J. Nuhfer, the Chief of Municipal and Industrial NPDES
Section of Region IV of the Environmental Protection Agency, we understand that this

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RECEIVEDIDENRIDWR Mr.Jeff Poupart
September 30, 2014
OCT 03 2014 Paget
Water Quality
Permitting Sectinr
departure comes at the request and direction of EPA for the purpose of addressing its
concerns.
Duke Energy will, of course, abide by this change. However, for the reasons set
forth below, we believe that it is imperative for DENR, EPA and Duke Energy to meet to
discuss and resolve the decanting of inactive basins as soon as possible so that closure
and other essential maintenance, inspection and repair work may proceed
expeditiously.
Duke Energy appreciates the acknowledgement in Mr. Nuhfer's letter that
expediting closure of inactive ash basins is a "worthy goal." Removing free-standing
water from inactive basins will expedite Duke Energy's ability to perform any
maintenance work needed to ensure basins continue to perform safely and reliably until
closure, such as slip-sleeving or permanently closing pipes. Finally, Duke Energy has
been directed by the General Assembly of North Carolina to remove ash from the
basins at Riverbend, Asheville, Sutton and Dan River within sixty months. Requiring
free-standing water to remain in these basins will not only delay the process for drying
out the ash that is necessary before any excavation may occur, but as a practical matter
could make meeting this deadline impossible.
Unfortunately, withdrawal of DENR's letter has caused uncertainty surrounding
regulatory requirements for moving forward with essential steps related to both closure
and continued safe operations. Duke Energy is concerned that imposing a formal
permitting process on the movement of free-standing water will substantially delay
taking action on these matters. As such we suggest discussions take place between
EPA, DENR and Duke Energy as soon as possible with a goal of identifying the
regulatory framework that will allow this work to move forward.
Duke Energy knows that DENR understands and appreciates the issues noted
above. Duke Energy is committed to working with DENR and EPA to take the
necessary engineering, scientific and environmentally sound steps to address ash
basins and comply with the mandates of the elected officials of North Carolina.
Sincerely,
arry K. Sideris
Senior Vice President
Environmental, Health & Safety

• •
Mr.Jeff Poupart
September 30,2014
Page 3
cc: Donald R. van der Vaart, DENR
Thomas A. Reeder, DENR
John Evans, Esp. General Counsel