NC0004961_Review of Draft_20150511

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Mr. S. Jay Zimmerman F►Esc�
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Division of Water Resources otO pf'ec
North Carolina Department of Environmental and Natural Resources
1617 Mail Service Center
Raleigh,NC 27699-1617
RE: Review of draft National Pollutant Discharge Elimination System permits for Duke Energy
Carolinas, LLC: Riverbend Steam Station,NPDES Permit Number NC0004961;
Plant Allen Steam Station, NPDES Permit Number NC0004979; and Marshall Steam Station
NPDES Permit Number NC0004987
Dear Mr. Zimmerman:
On March 6, 2015, the above-referenced draft National Pollutant Discharge Elimination System
(NPDES) permits and fact sheets were received by the United States Environmental Protection Agency
from the North Carolina Department of Environment and Natural Resources, Division of Water
Resources (DWR).
On March 31, 2015, in accordance with Section IV. B. 3 of the Memorandum of Agreement(MOA)
between the State of North Carolina and the EPA, 40 Code of Federal Regulations (C.F.R.)§123.44(a),
the EPA provided a written notice that it would exercise its right to a full 90-day review period as
authorized by the MOA and federal regulations. The EPA has completed its review of the draft permits
and is providing notice of its comments and recommendations with respect to the draft permits in
accordance with MOA Section IV(B)(3) and 40 C.F.R. §123.44.
The draft permits would authorize discharges from ash ponds at the three plants. Based on a review of
the draft permits, fact sheets, and other information provided by DWR, we understand that the permits
will authorize not only the previously permitted discharges from the engineered outfalls at the ash
ponds, but would also authorize previously unpermitted seeps that reach surface waters from the ash
ponds. Our understanding is that some seeps occur from the ash pond berms and are engineered to occur
in order to maintain the structural integrity of the impoundments. We refer to such as engineered seeps.
In other cases, seeps occur as a result of communication between the base of the impoundments and the
groundwater table, which results in the emergence of seeps at locations remote from the ponds, which
then flow to surface waters. We refer to these seeps as un-engineered seeps.
We further understand that un-engineered seeps will be addressed in the long term through closure
requirements under the North Carolina Coal Ash Management Act, but that DWR is proposing, as an
interim measure only, to better monitor and manage un-engineered seeps through NPDES permits. To
do so, DWR has included provisions in the draft permits to make all seeps subject to the same
technology effluent limits that would apply to the engineered outfalls, and DWR has also included
monitoring requirements for determining flow and pollutant composition of the seep discharges
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and ensuring that effluent limits are not exceeded. In addition, we understand that the permits address
water quality concerns by capping the flow quantity that may be discharged via seeps. Further,we
understand that the permits will include and require implementation of a Plan for Identification of New
Discharges so that new seeps are identified when they occur.
We have specific comments and recommendations for improving the permits. Because this letter
transmits comments relating to three different draft permits, and our comments are in some cases plant-
specific,we are providing four separate enclosures which provide general and facility-specific
comments and recommendations for the three draft permits.
In accordance with the MOA and 40 C.F.R. §123.44,the EPA submits the attached comments and
recommendations on the draft permits. The EPA requests that DWR revise the permits and fact sheets to
address these comments and recommendations. If you have any questions,please call me at(404) 562-
9345 or have your staff contact Ms. Karrie Jo Shell in the NPDES Permitting Section at(404) 562-9308.
Sincerely,
Jlc _ LI---
am s I Giattina
4 Dir;ctor
JWate 'rotection Division
Enclosures(4)
cc: Mr. Harry Sideris, Senior Vice President
Duke Energy Carolinas, LLC

•
Enclosure 1
General comments on draft NPDES permits for Plant Allen Steam Station. Riverbend Steam Station
and Marshall Steam Station
1. There is a state-wide mercury impairment and all the external outfalls in all the permits should
have a mercury limit that protects water quality. NC's instream WQS for mercury is 0.012 ug/I
for fresh waters. See EPA's letter to NCDENR dated September 6,2012, regarding permit
recommendations to address statewide mercury impairment.
2. The use of NC's Mercury Total Daly Maximum Loading(TMDL) limit of 47 ng/I (based on fish
tissue) is inappropriate because NC has not fully demonstrated the discharges from the Duke
facilities are not causing or contributing to a violation of the NC WQS of 0.012 ug/I of mercury.
As stated in EPA's September 6,2012, letter to NC regarding permit recommendations to
address statewide mercury impairment,a less stringent permit limit that protects WQS would
only be justified once the NCDENR first demonstrates that site-specific data show that the
facility(ies)are not causing or contributing to the existing mercury impairment.
3. All permit parameters should include units of measurement.Several parameters that only have
monitoring requirements do not indicate the unit of measurement.
4. The draft permit should specify that EPA methods 200.7 or 200.8(or the most current versions)
be used for analyses of all metals except for total mercury.
5. The draft permit should ensure that all effluent samples are representative(see 40 CFR
122.41(j)).Therefore, language should be included to clarify that all effluent samples for all
outfalls shall be taken at the most accessible location after final treatment but prior to discharge
to waters of the U.S.
6. Each permit contains a seep pollutant analysis provision.The draft permits should require that
all seeps covered under Outfall 010(combined seeps) be monitored no less than monthly
throughout the entire permit term. Reducing the frequency from monthly to bi-annually after
the first year should not be allowed because monitoring bi-annually is not frequent enough to
capture changes that may occur in concentration levels.The permits should also specify how
seep flow rates will be measured/estimated.As written,the permit is unclear as to whether the
permittee should monitor every seep and submit an average for all monitored seeps or if it
allows the permittee to choose which seep to monitor and report on the DMR.The latter
scenario would not allow the permitting authority to ensure that the effluent limits are being
met and protective of human health and aquatic life.The permittee should monitor every seep
during NPDES compliance monitoring events pursuant to the NPDES permit and report the
individual results on a DMR. However,an average could be used to demonstrate compliance
with the effluent limits at Outfall 010,provided every seep is monitored and reported.
7. The fact sheets should disclose that there is a state-wide impairment for mercury and should
discuss the mercury Total Maximum Daily Load (TMDL).
8. All the fact sheets lack a discussion of the justification for all the proposed limits and conditions
for each parameters at each outfall. Per 40 Code of Federal Regulations(CFR) 124.56,fact
sheets should contain any calculations or other necessary explanation of the derivation of
specific effluent limitations and conditions as well as explanations for limits for toxics,internal
waste streams,indicator pollutants,case-by-case determinations,and waivers.

9. The discussion of the Reasonable Potential Analyses(RPA)(attached to the fact sheets)should
disclose the results of background instream sampling results for metals used in the RPA
calculations. We suggest attaching any background sampling results to the permit fact sheets.
The fact sheets should also discuss the analytical methods used for all parameters.We
recommend EPA method 200.7 or method 200.8 be used for metals other than mercury.
10. The following studies/evaluations are mentioned in the permits but should be attached as part
of the permit to ensure enforceability;(a) Fish Tissue Monitoring Plan,and (b)the Plan for
Identification of New Discharges.Specifically,the front cover page should include appendices A
and B in parentheses after"Part I".
11. The Fish Tissue Monitoring Plans for each facility should require more frequent sampling than
once every five years.We recommend annual sampling.
12. The Plan for Identification of New Discharges should be revised,as follows:
a. The Plan should include a rationale for selecting the proposed areas to be inspected for
seeps. It is unclear how the current inspection area was determined.The areas for
inspection should encompass all the areas where seeps could potentially be located.
Specifically,we recommend the inspections include all areas below the topographic
contour which corresponds to the full pond elevation in the vicinity of the ponds in all
directions.
b. The Plan discusses a site conceptual model; however,it does not appear that this model
was used in the delineation of areas to be inspected for seeps. The presentation would
benefit from a more comprehensive conceptual model for the hydrology such as is
found in "The Piedmont Ground-Water System" by Ralph C. Heath in Groundwater in
the Piedmont: Proceedings of a Conference on Ground Water in the Piedmont of the
Eastern United States,edited by Charles C Daniel II et al, Clemson University, 1989.
Data and information from the site should then be used as input into the delineation of
areas for inspection for seeps. For example,at the base of the saprolite zone just above
bedrock there is typically a higher permeability zone and it is likely that groundwater
would be found in this area.When monitoring wells are drilled it is usually very obvious
to the driller when bedrock is encountered because drilling becomes much more
difficult. Data on the depths of that zone at the site could be extrapolated to the
topographic maps where it would outcrop at the surface.The expected locations of the
higher permeability zone at the site could be useful in helping to delineate areas where
seeps potentially could be located.Similarly any data on depths and orientation of
bedrock fractures at the site could be useful in helping to determine likely areas for
seeps.The same goes for any information about relict features in the saprolite and
information about geologic dikes.
c. Some of the background locations at the sites may not represent ambient background;
therefore,more consideration should be given towards appropriate background
conditions. Most notable is the background location at the Riverbend Steam Station Ash
Basin,which appears to be located topographically downhill from an access road to the
ponds.
d. The sampling protocol is inadequate. It is recommended that the EPA Region 4 Support
and Ecological Service Division sampling protocol for surface water be adapted for this

site or followed as closely as possible. It can be found at
http://www.epa.goviregion4/sesdifbotp/Surfacewater-Samoling.pdf
e. Figure A-1 should be revised. It does not accurately depict identification of un-
engineered seeps that are occurring and reaching waters of the U.S. We suggest the
following changes:
i. The question in the first diamond should be revised to read:"Is new seep
located below the full pool elevation of the ash basin?"
ii. The second diamond should be deleted because we recommend that seeps in
all directions from the ash pond be identified, not just the ones that are located
"within the slope-aquifer boundary system."
iii. The question in the third diamond should be revised to read:"Does new seep
present flow that can be collected,estimated,and sampled?"We further
recommend footnotes be included to describe how the flows will be collected,
where the samples will be taken,and how the flow rates will be estimated. It is
imperative that this be done in a way as to not exclude seeps because of
ambiguity regarding collection,sampling locations,and flow rate
measurements.
iv. The third rectangle(immediately following the third diamond)should include
flow rate as a parameter.Also,we recommend the facility use a tracer to
specifically identify wastewater constituents that may be in ash. Recent
research results suggest that the use of boron and strontium isotopes are
helpful in specifically identifying wastewater from coal ash impoundments
(Ruhl, Dwyer, Hsu-Kim, Hower,&Vengosh,2014).
v. The forth rectangle should include a footnote that contains information on the
decision-making criteria that will be used.This would reduce ambiguity.
13. Outfalls 002A and 002B are for emergency overflows.The stated measurement frequency is
"episodic",and the permit states that,"Episodic sampling is required per sump overflow
occurrence lasting longer than an hour." Monitoring for these discharges must be
representative.Allowing sampling after the first hour is not justified.Therefore,the permittee
should not be allowed to discharge during the first hour without collecting a sample,and the
term "episodic' in the table should be replaced with"per discharge event." Lastly,the permit
allows effluent samples to be collected "at a point upstream of the discharge". In accordance
with 40 CFR 122.41(j),this provision should be revised to require that effluent samples be taken
at the most accessible location after final treatment but prior to discharge to waters of the U.S.
14. For all outfalls where the flow measurement is to be"estimated",the permit should specify how
the facility will determine this estimate.
15. The fact sheets for each permit should include calculations regarding the instream waste
concentrations used to determine the dilution for WET testing.Specifically, it is not clear which
effluent flow—long term average,monthly average or daily maximum—were used in
conjunction with the 7Q10 flows to calculate the percent effluent concentrations to be used for
WET for each facility.

Enclosure 2
Specific comments for the draft NPDES permit NC0004979 for Plant Allen Steam Station
1. For outfalls 002,002A,002B,and 011,the footnote pertaining to limits for total copper and total
iron should be revised to read:"The limits for total copper and total iron only apply when
chemical metal cleaning wastewaters are being discharged."
2. Footnote 4 for outfall 010 and footnote 5 for outfall 011 should be revised to read: "The limits
can be met by installation of a wastewater treatment system,by re-routing the discharge to the
existing treatment system,or by eliminating the discharge."
3. The definition for low volume waste in special condition Part I.A.(13)should be revised to clarify
that 40 CFR 423.11(b)that low volume wastes is a term that includes waste streams for which
there is no specific effluent guideline per 40 CFR 423. •
4. For outfall 010,the sample type for flow is"grab."The permit should require the permittee to
estimate flow based on calculations or some other pre-determined method for estimating flow
rate.
5. Page 5 of the fact sheet states that the technology-based effluent limitations(TBELs)developed
by NC DENR for the flue gas desulfurization wastewater would be met by"the end of 2019."
Therefore,footnote 4 for outfall 005 in the permit should be revised to require the TBELs be met
no later than December 31, 2019.
6. Special condition I.A.(19), Monitoring of the Receiving Water,should specify that the up-and
down-stream sampling locations will be at the nearest accessible locations to Outfall 002.
7. The fifth item under Part I.A.(13)should be revised to require the permittee to report any
leakage detected during dike inspection as soon as practicable to NCDENR and to the NC Dam
Safety program office.
8. For clarification,the permits should contain definitions for the following terms per 40 CFR
423.11:
a. "Chemical metal cleaning waste means any wastewater resulting from cleaning any metal
process equipment with chemical compounds, including, but not limited to, boiler tube
cleaning."
b. "Metal cleaning waste means any wastewater resulting from cleaning[with or without
chemical cleaning compounds]any metal process equipment including, but not limited to,
boiler tube cleaning, boiler fireside cleaning,and air preheater cleaning."

•
Enclosure 3
Specific comments for the draft NPDES permit NC0004987 for Marshall Steam Station
1. The topographical map is unreadable.
2. Footnote 1 on Page 3 of permit is confusing. It states that a permit modification is needed
before the facility can chlorinate; however,the effluent limitation limits table already includes a
limit for free available chlorine.
3. Footnote 2 on page 4 allows a variance from the daily maximum limit total suspended solids
(TSS)of 20 milligrams per liter(mg/I).The permittee is allowed to discharge a daily maximum
TSS concentration no greater than 40 mg/I if it can demonstrate that TSS concentration in the
intake water results in a TSS effluent concentration between 20 el to 40 mg/I. The permit
needs to include a requirement addressing how the permittee must do this demonstration,and
the fact sheet should provide a justification for this allowance.
4. For outfall 010,there is no requirement to measure and report flow rate.The permit should
require the permittee to estimate flow based on calculations,or some other pre-determined
method for estimating flow rate.
5. The fact sheet should explain the justification for using a 7Q10 flow of 60 cubic feet per second
(flow during releases)to determine the instream waste concentrations used for WET purposes.
Typically,the 7Q10 for a lake is zero.

•
Enclosure 4
Specific comments for the draft NPDES permit NC0004961 for the Riverbend Steam Station
1. For outfall 010,the sample type for flow is"grab."The permit should require the permittee to
estimate flow based on calculations or some other pre-determined method for estimating flow
rate.
2. Footnote 2 on page 4(Outfall002)and footnote 1 on page 14(Outfall 011)allow a variance from
the daily maximum limit total suspended solids(TSS)of 23 mg/I.The permittee is allowed to
discharge a daily maximum TSS concentration no greater than 43 mg/I if it can demonstrate that
TSS concentration in the intake water results in a TSS effluent concentration between 23 g/I to
43 mg/I. The permit needs to include a requirement addressing how the permittee must make
this demonstration,and the fact sheet should provide a justification for this allowance.
3. For outfalls 002,002A,and 011,the footnote pertaining to limits for total copper and total iron
should be revised to read: "The limits for total copper and total iron only apply when chemical
metal cleaning wastewaters are being discharged."
4. During ash pond dewatering operations(page 5),monitoring frequency for all parameters
should be no less than weekly in order to ensure that permit limits are being met as wastewater
levels decrease in the pond and concentrations of metals and other parameters increase. Duke
Energy has proposed additional measures to be undertaken during pond dewatering,including
continuous real time per discharge monitoring and other protective measures(limits on rate of
pool lowering and automatic pump shutoff for exceedance of effluent limits,especially TSS).
These measures will be unenforceable without a permit mechanism,and should be included as
conditions in the permit.
5. For outfall 010,the sample type for flow is"grab."The permit should require the permittee to
estimate flow based on calculations,or some other pre-determined method,for estimating flow
rate.
Reference
Ruhl, L. S.,Dwyer,G. S., Hsu-Kim, H., Hower,J. C.,and Vengosh,A. (2014). Boron and strontium
isotopic characterization of coal combustion residuals:Validation of new environmental
tracers.Environmental Science Technology,48, 14790-14798.doi: 10.1021/es503746v