NC0000396_Decanting of Water to JP_20140916 (2)

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;�; t1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4
° " ATLANTA FEDERAL CENTER
i; 0 61 FORSYTH STREET
�yItPnolft. ATLANTA, GEORGIA 30303 -8960
SEP 16 2014
Mr. Jeff Poupart
Chief, Permitting Section
Division of Water Quality
North Carolina Department of Environment
and Natural Resources
1611 Mail Service Center
Raleigh, North Carolina 27699 -1611
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um SEP 22 2014
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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
RECEiVED1DENRiDWR
SEP 2 2 2014
Water Quality
Permitting Section