NC0004961_Review of Proposed Final Permit (EPA)_20160210

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J�,SEO STgTFs UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
.YV. REGION 4
p iATLANTA FEDERAL CENTER
z o� 61 FORSYTH STREET
ATLANTA, GEORGIA 30303-8960
FEB 10 2016
Mr. Jeff Poupart
Chief, Water Quality Permitting Section
North Carolina Department of Environmental Quality ���
Division of Water Resources R E
1617 Mail Service Center
Raleigh, North Carolina 27699-1617 APR 2 5 2016
DWR SECTION
Re: Review of Proposed Final Permit INFORMATION PROCESSING UNI i
Duke Energy Carolinas, LLC, Riverbend Steam Station
National Pollutant Discharge Elimination System Permit NC0004961
Dear Mr. Poupart:
On March 6, 2015, a draft National Pollutant Discharge Elimination System (NPDES) permit and
supporting documents for the above referenced facility were received by the U.S. Environmental
Protection Agency from the North Carolina Department of Environment and Natural Resources (NC
DENR), Division of Water Resources (DWR). NC DWR provided a public comment period for the draft
permit and supporting documents from March 6 through May 5, 2015. The EPA completed its review of
the draft permit and provided its comments and recommendations with respect to the draft permit in a
letter dated May 11, 2015.
The EPA received a proposed permit from NC DWR via email on May 26, 2015, and provided
comments to NC DWR on June 10, 2015. These comments included a recommendation that NC DWR
investigate whether additional waterbodies which receive discharges of wastewater are present at the
facility and make appropriate changes to the proposed permit based on the outcome of that investigation.
On September 11, 2015, NC DWR responded to the EPA's comments with a revised permit which
included new proposed language addressing discharges from seeps. In lieu of written comments, the
EPA and NC DWR discussed the complexities of permitting discharges from seeps during an October
22, 2015, videoconference.
Subsequently, on November 12, 2015, NC DWR transmitted a final proposed NPDES pen -nit which
included a revised approach to permitting discharges from seeps. In accordance with the EPA/NC
DENR Memorandum of Agreement, on November 24, 2015, EPA notified NC DWR of the need for a
90 -day review period. On February 4, 2016, the EPA and NC DWR participated in a telephone
conference to discuss clarifications to the final proposed permit. In a February 5, 2016, email the EPA
requested that NC DWR provide a revised proposed final permit that addressed the specific issues that
were discussed:
Internet Address (URL) • http //www.epa.gov
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or
1. EPA and DWR agree that each seep is treated as a distinct outfall (Outfalls 101-112).
2. The Permit should state the applicable technology-based effluent limits and water quality -based
effluent limits that apply to each identified seep. EPA recommends that the Permit contain an
effluent limitations table for the seeps that includes effluent characteristics, numeric effluent
limits or Action Level requirements, measurement frequency, sample type, sample location,
analytical test method, etc.
• For all seeps, the technology-based effluent limits should be the applicable effluent
limitations guidelines for Total Suspended Solids and Oil and Grease.
• For the ten seeps identified as emerging within jurisdictional waters, the water quality—based
effluent limits should be the applicable water quality standard.
• For the two seeps that emerge on dry land and flow to jurisdictional waters, the exact
location where the seep enters a water of the U.S., and therefore the assimilative capacity of
that receiving water, is not included in the Permit. Therefore, a conservative approach is to
establish the same water quality -based effluent limits for the non jurisdictional seeps as for
the jurisdictional seeps, i.e., the water quality—based effluent limits should be the applicable
water quality standard. The permit could include a provision that addresses the applicability
of the effluent limits if the permittee can demonstrate that the seep does not discharge to a
water of the U.S. or does not carry pollutants indicating coal ash characteristics.
3. The Permit should clarify that the Permittee shall commence monthly monitoring of seeps upon
the effective date of the Permit. Monitoring results that show an exceedance of an applicable
water quality -based effluent limit or technology-based effluent limit will be a violation of the
Permit.
4. EPA recommends that the monitoring frequency for all seeps be monthly for no less than one
year before reducing to quarterly monitoring. Any seeps that exceed an applicable water quality -
based effluent limit or technology-based effluent limit should continue monthly monitoring.
5. The Permit should require that all monitoring results for each seep be submitted on a Discharge
Monitoring Report form.
6. The proposed Permit (Part A.16) requires the Permittee to implement one of three options to
address seeps which result in violations of water quality standards. For example, one option
allows the Permittee to demonstrate through modeling that the seep will be eliminated by
decanting and dewatering. The Permit is unclear as to whether this demonstration, once made,
relieves the Permittee from the obligation to comply with the water quality -based effluent
limits. The final Permit should be revised to clarify that all effluent limits, including water
quality -based effluent limits, remain applicable notwithstanding any action by the Permittee to
address the violation through one of the identified options, so that any discharge in exceedance
of an applicable effluent limit is a violation of the Permit as long as the seep remains
flowing. We understand this to be the intent of the Permit as drafted but a clarification is needed
to ensure that there is no uncertainty regarding this issue and that the effluent limits remain
enforceable.

7. In addition to the limits and conditions stated on page 4 of 16 for Outfall 002, all of the
conditions required in NC DWR's December 17, 2015, authorization for decanting at the
Riverbend facility should also be in included in the Permit. We note that the following conditions
should be added:
• discharge rates during decanting will be lower than average historical discharge rates from
the permitted outfall;
• use of a floating pump station with free water skimmed from the basin surface using an
adjustable weir;
• daily monitoring of flow;
• continuous monitoring of TSS with auto pump shut-off if TSS concentration (15 minute
average) exceeds half the maximum daily TSS limit. Pumping will be allowed to continue if
interruption might result in a dam failure or damage;
• real time pH monitoring with an auto shut-off if the 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;
• during pumping, in addition to the monitoring for effluent limits required in Part A.(2.),
weekly monitoring for the following parameters shall be performed using the most sensitive
EPA approved methods (e.g., EPA method 200.7 or 200.8 for metals): total chromium, total
lead, total cadmium and total dissolved solids.
8. In addition to the parameters listed in Part A.(13) - Instream Monitoring Requirements, the
Permit should also require sampling for total hardness.
9. Appendix A (Seep Identification Plan dated June 23, 2015) should be attached to the Permit.
In response, NC DWR transmitted via email a revised proposed final permit to address the EPA's
continents. The EPA has reviewed the February 8, 2016, revised proposed final NPDES Permit
NC0004961, pages 1 - 27. The revisions have provided the clarification that EPA sought to ensure a
clear and enforceable permit. The EPA has no further comments.
I want to express my appreciation for all the work that you and your staff have done to resolve these
very complex issues. We look forward to continuing our collaborative work. If you have any questions,
please do not hesitate to contact me at [phone] or Ms. Denisse Diaz at [phone].
Sincerely,
ames D. Giattina
Director
Water Protection Division
cc: Duke Energy