Allen Steam Facility - Duke Energy

NCDENR
North Carolina Department of Environment and Natural Resources
Dnq^rl,, C:nk1c n Dni rn
;-)-.-ily • ans r due
Governor
Mark McGary
Senior Engineer
Duke Energy Carolinas, LLC
P.O. Box 1006, Mail Code EC13K
Charlotte, North Carolina 28201
Dear Mr. McGary:
Division of /Water Quality
Ohnr1:nV
les alkIld, P.
Director
March 21, 2012
Dee Crpn y��n
Secretary
Subject: Draft NPDES Stormwater Permit
Permit Nos. NCS000546, NCS000548,
& NCS00549
Duke Energy Carolinas, LLC -
Plant Allen, Marshall Steam Station,
and Riverbend Station
Gaston and Catawba Counties
Enclosed with this letter is a copy of revised draft NPDES stormwater permits for these three
facilities. Please review the draft permits very carefully to ensure thorough understanding of the
conditions and requirements each contains.
Thank you for meeting with us last November to discuss your questions and concerns with the
proposed stormwater permits for these facilities. As we explained, efforts to permit coal-fired
power plants consistently across the state led to a comprehensive stormwater monitoring scheme
for all such plants. The original draft permits for these sites contained the same requirements as
other NDPES stormwater permits issued for coal-fired power plants since 2009.
We also hope we clarified the intent and flexibility of designating outfalls with "Representative
Outfall Status" (ROS) to alleviate the company's concerns about that process. We will continue to
work with you and the Mooresville Regional Office during this draft permit stage to establish ROS
for the most appropriate outfalls at these sites. With this letter, we are transmitting our proposed
ROS designation at each site. We invite further consultation with you and the regional office to
reach a mutual resolution if necessary.
1617 Mail Service Center, Raleigh, North Carolina 27699-1617
Location: 512 N. Salisbury St. Raleigh, North Carolina 27604
Phone: [phone] FAX: [phone]
Internet: www rimaterquality.orq
An Equal Opportunity i Affirmative Action Employer
ne
NorthCarolina
Natmrall#

Duke Energy Carolinas, LLC
March 21„2012
Page 2 of 9
Changes to Draft Permits
These permits reflect a newer NPDES stoerriwater permit template, which the Stormigater
Permitting Unit (SPU) implemented for all industrial stormwater permits this year (not just power
plants). Standard changes'include the requirement to monitor during a "measureable storm event,”
rather than "representative storm event." Based on our discussion at the November,meeting and
your comments, we have also proposed revised monitoring requirements. 'These'changes reduce
metals monitoring significantly. The Division will continue to structure stormwater permits for all
coal-fired power plants as consistently as'possible across the state.
These permits contain monitoring for conventional pollutants COD, TSS, 0&G, and pH because
they are general indicators of potential,stormwater contaminants at these types of sites Data,from
permitted power plants and new permit applications indicate these parameters sometimes exceed'
or fall outside of benchmark ranges. The pH is also critical to characterizing toxicity of,metals.
These draft permits also include monitoring formercury (Hg) and selenium (Se). Both metals are
in coal combustion waste ash, a potential stormwater contaminant at these sites All waterbodies in
the state a"re impaired for mercury, and a.statewide mercury TMDL is under development. Studies
by N.C. State University researchers suggest that selenium may be taken up in fish in preference,to
mercury at locations in close proximity to coal-fired power plants (Sackett et al., 2010). Regional
deposition may influence,mercury discharge concentrations, and therefore field blank data must be
reported. DWQ has not identified'a conflict with sampling during a stormwater�event and
employing Method 1631 for analysis when the intent is to characterize stormwater discharges (and
not uncontaminated wastewater discharges).
Permits for these sites will include aluminum (Al) monitoringaf sample results submitted with the
application exceed the stormwater benchmark concentration of 0.75 mg/l, or if no data are
available'. North Carolina does not currently have awater quality standard for aluminum, but there
are federal recommended water quality criteria. An aluminum, benchmark will,not apply unless
the waterbody is ever impa'ired`for aluminum or for biological'integrity.
Power plants discharging stormwater to waterbodies impaired.for copper (Cu); zinc (Zn), or
other priority pollutant metals will monitor for those metals. Biological impairment also
prompts copper and zinc monitoring, and possibly other metals associated with coal ash.
Exceptions maybe made (and monitoring required) for' metals or other toxicants, for plant sites
discharging to waterbodies that are not impaired if data or other information evidences a possible
problem with storm waterdischarges. However, in general, these permits will not require
monitoring for all priority,pollutant metals as originally proposed.
There is no benchmark that triggers monthly monitoring for mercury. Also, sampling for metals
maybe discontinued after four consecutive samples are below the benchmark,or below 12' ng/l of
mercury. Where applicable, these permits offer alternatives to copper and zinc benchmarks (see
Part I1, Section B.)'. 'Insome cases,'nutrient monitoring (total riitrogen and/or total phosphorus)
will apply'because of nutrient,prdblems in the river basin. The draft'permit for Plant Allen includes
annual nitrogen and phosphorus monitoring because of,nutrient concerns in the Catawba River
basin and Lake Wylie.

Duke Energy Carolinas, LLC
March.21, 2012
Page 3 of 9
These draft permits allow qualitative monitoring to be limited to representative outfalls,if the
remaining outfalls can be observed once per the permit term. Exceptions may be made where the
regional office agrees outfails are truly inaccessible or cannot be made safe without excessive
burden on the permittee; or the regionahiffice determines some outfalls warrant more periodic
observation. + -
Plants Shutting Down
Draft,permits for plants scheduled to shut down within the five-year permit term will include
monitoring for the same parameters based on the criteria explained above. Annual sampling
without benchmarks that trigger monthly monitoring is proposed for the Riverbend Steam
Station, contingent on the company submitting a plan within six months of the permit effective
date to outline'the shutdown schedule and clean-up details This plan should include a
demonstration that past or present industrial activities will longer have'the potential to pollute
stormwater.
Please note that the Division is still obligated to review any request for permit.rescission and to
consider site conditions after the shutdown before approving the request The Division may also
require more frequent monitoring at a plant scheduled to shutdown if discharge data,or in -stream
data justify concern about in -stream standard violations
Comment Period
Because of the significanttchanges, the Division will re -notice these revised' draft permits for
another public comment period. We are also appending responses to comments Duke Energy
submitted on each oftheseplant's-original draft permits (see attached). We hope this information
will answer some of the questions that remained after our initial meeting with you last fall. We
welcome the opportunity to meet with you, again to discuss the°proposed permits during the 30 -day
public notice period.
Please submit any comments to the appropriate_ Stormwater Permitting Unit (SPU) contact no later
tharf thirty (30) days, followmg,your'receipt of the draft. Comments should be sent°to the address
listed at the bottom of this page. If no adverse comments are received from the public or'from you,
these permits will be issued in about two months, If you have any questions or comments,
concerning these draft permits, please contact,
Plant Allen - Bethany Georgoulias at(919) 807-6372 or [e-mail]
Marshall Steam Station - Brian, Lowther at [phone] or [e-mail]
Riverbend Steam Station - Robert.Patterson at [phone] or robert.patterson@ncdenr gov
Sincerely,
54)1� r>"Wl
Bradley Bennett
Supervisor,'Storinwater Permitting Unit
,cc: Mooresville Regional Office, Water Quality Section (w/attachment)/ M. Parker
Stormwater Permitting Unit
Attachments

Duke Energy Carolinas, LLC
March 21, 2012
Page 4 of 9
References
Sackett, D.K , D. D. Aday, l.A. Rice, W;G. Cope, and D. David Buchwalter, 2010, Does proximit-� to coal-
fired'power plants influence fish tissue mercury? Ecotofdcology 19:1601-,1611. DOI-
10.1007/s10646-010-0545-5.

Duke.Energy,Carohnas, LLC
March 21, 2012
Page 5 of 9
Respo'n"s,e, toComments from Duke Energy on Previous Draft Permits
Plana Allen - IVCS00054. 6
Comments on the draft permit were received September 15, 2011, and subsequent comments
were received via e-mail on November 18, 2011. We,have tried to,address many of these
comments below.
With its permit application, the company requested representative outfall status (ROS) for four
stormwater discharge outfalls. The Mooresville Regional Office has recommended'approval with
some modifications. The, recommendations include approval of IiOS for SW005, SW008, SW011
and SW015' (instead of SW0'18).
• SWO05 represents outfalls'SW002„SW004 - SW006, SW014, and Group SW017.
• SW008 represents outfalls SW001,,SW003, SWO0.7 - SW010, and Group SWO13
• SWO11 represents outfalls SWO11 and SW012.
• SWO15 represents outfalls SW016, SW018, and SW020
The draft permit also includes a special footnote for SWO11 and SWO12 because discharges
commingle with wastewater outfall flows. Because ofa'lack=of recent analytical data, -the- Region
has advised a short-term period of sampling at some of the outfalls represented by this group,
including outfalls SW002, SW007,, SW009, SW010, and SW012. The Division is proposing two
sampling events in the first year of the permit for these outfalls. However,.the draft permit
does not contain conditions specifying that sampling.
DWQ'typically handles representative outfall status (ROS) designation outside of the permit
because that status (and the relief from monitoring other outfalls) is subject to change if activities
or other circumstances change. Otherwise, the permittee would have to,go through the process of a
permit modification every time ROS changed. With our current process, designations of, and,any
changes°to ROS can be`handled,more expeditiously without reopening a permit for modification.
The Division -will verify ROS approval and temporary monitoring requirements in the cover letter of
the issued permit, unless the company prefers to include these specifications in the final permit.
Your letter'in September 2011 listed numerous outfalls on the plant property that Duke'Energy
feels are not part of the industrial use areas,and should be excluded from the permit. Those outfalls
are`SW001, Group SW013, SW014, Group SW017, SW019, and SW020.
Response: 'The company,may have a better understanding of which outfalls do,not drain runoff
associated with industrial activitysmce our November meeting The NPDES stormwater permit
applies to all stormwater outfalls associated with industrial activity, itis the permittee'
-s
responsibility to identify all appropriate discharge outfalls in the Stormwater Pollution Prevention
Plan (SPPP) and to conduct sampling as necessary Please not&thatrnagmtude of risk to surface
waters does not determine whether or not a,stormwater discharge is subject to the NPDES permit
Applicability is determined by whether that discharge'is.associated with industrial activities. For a
definition of "Stormwater Associated with I ndustri al. Activity,” please refer to the DEFINITIONS
sectiomin Part Vl'of the permit and to 40 CFR §12226 (b)(14) The Division will be happy to help
you with any questions,about whether a drainage area falls into that,category or`not

Duke Energy Carolinas,,LLC
March 21, 2012
Page,6,of 9
The,company commented that several stormwater outfalls,are cur,rently'inaccessible, and that
there are concerns about safe and secure access to theses outfalls for sampling and monitoring. For
exaniple, you indicated sampling from Group SW0113 and Group S` O17 Was norfeasible.
Response: Most'of the outfalls listed will be represented by other,outfalls, with,the exception of
SWO12 The Mooresville Regional Office (MRO) has advised short-term analytical sampling for
SW012, and the Central Office is recommending sampling during the first year only Attached to the
comments was a,photo of,SWO12 that noted sample collection probability was "likely" if sampled
upstream of the outlet because it is submerged This approach is acceptable We understand your
concerns about safety and secure, access to outfalls, avid we fully support taking caution iii order to
make sure outfalls are accessed safely. We encourage sampling at the nearest, safely accessible
location upstream of a stormwater,outfall when it is necessary
Duke Energy's comments,in,September 2011 addressed many concerns about the,list of,analytical,
monitoring parameters and lack of a basis for the proposed monitoring. Your comments express
the opinion that the ash basin discharges of wastewater should represent "the worst;case impacts
to surface waters in terms of mass loading associated with the facility.
Response: The NPDES wastewater permits are developed with the benefit of a considerable
amount of historical data. With those data, staff can do a reasonable potential analysis -and
determine whether monitoring a parameter is warranted for wastewater flows, which are also.
permitted at'a maximum flow rate. Typically no maximum flow rates are established for
stormwater discharge outfalls, and the amount of stormwater data from this plant site is very
limited Only two stormwater samples—each from a different outfall—were submitted.with the
permit,application, and data.from any other samples,for previous NPDES wastewater,permit
renewals were not provided As a comparison, typically a minimum of 8-10 samples are required
for a reasonable potential analysis of wastewater,concentrations Please see therevised list of
parameters in the attached.draft permit and discussion on p. 2 to understand how,the Division has
addressed„this concern,
In its comments, the company was concerned that there was no scientific justification for many'of
the benchmark values and suggested,that a water quality,issue, such as a 303(d) listing
(impairment), should drive the need for a benchmark. The comment letter requested that the
benchmarks that do not relate to actual existing water quality issues in the receiving water body be
removed. The company expressed, concern that exceeding a benchmark�would give the,appearance
to third parties that a water quality standard had been violated,
Response: The stormwater benchmarks,(or "triggers” for additional stormwater management
responses) are not the same as effluent,limits, and exceeding those values is not a violation of the
NPDES stormwater permit Renchinarks;are intended,asa tool for the permittee to evaluate the
effectiveness of BM Ps and flag.possible stormwater contamination problems- The Division has
incorporated flexibility in Tier' 3 of the permit to work with the permittee in a'd'dressing i'ssuIes,
including ameliorating monitoring requirements when appropriate
Benchmarks are determined with guidance from the Division's, Classification and Standards Unit
and use data from multiple sources, including'EPA's National Recommended.Water Quality Criteria
and N C'. Surface Water Quality Standards (found in 15A NCAC ,02B Rules) When rules or
regulations do not contain information fora pollutant of concern, benchmarks may be calculated
per 15A NCAC 2B 0200 usmg'peer-reviewed,toxicity data, other reference sources, and best

Duke Energy Carolinas, LLC
March 21, 2012
Page 7 of 9
professional judgment (BPJ) For toxics like metals, stormwater benchmark concentrations are
based on the Y2 Final Acute Value (FAV) or other value protective against acute impacts to aquatic
life whenever available Conventional pollutants in this permit (BUD, COD, O&G) are based' on the
secondary treatment standards in the federal regulations (40 CFR §133) In the Division's best
professional judgment, stormwater concentrations,ofthese ,pollutants that regularly exceed those
standards indicate a possible problem
The requirement to control the discharge of stormwater pollutants is established in federal rule and
North Carolina law; that requirement is not based on, establishingsimpact This,oversight is
consiSu nt il[h the Division's of ler programs The Divi.sion,llas ii-corporateu stormwatcr
benchmarks into industrial stormwater permits for the last four years, and it modeled the•tiered
response, approach after other states' programs Compliance with the,permit is establishedrby the
permittee responding°appropriately to`benchmark exceedances in the tiered structure
The company commented that EPA Method 1631 E low level mercury�analysis was not appropriate
for,stormwater sampling and requested the requirement'be removed,,or that it be replaced with
Cold Vapor Mercury Analytical Method 245.1.
Response: We understand the limitations of EPA Method 1631 E However; the, low level mercury
analysis is the only acceptable method,for measuring concentrations at the water,qual'ity standard
of 12 ng/1. Even though regional wet deposition may contribute to mercury concentrations
measured in stormwater discharges from this site, Method 245 1 is not likely to detect those
concentrations because its practical quantification limit (PQL) is only 0 2 µg/l DWQ has not
identified a conflict with sampling during a stormwater event and employing, Method 1631 for
analysis when the intent is to characterize stormwater discharges
In its comment letter, the'company requested that the Annual Summary DMR reporting
requirement (to the DWQ Regional Office) be removed.
Response: We are receptive to th&company's concern that this annual submittal was redundant
with the standard reporting°requirement to submit DMRs to the Central Office within 30 days of
receiving results This requirement has been removed from Part II, Section B, Table 2 (and' Part IdI,
Section E 2 )
The company's comments expressed dissatisfaction about the mandatory -60 -day separation
between concurrent sampling events (Part II, Section B.).
Response: The Division feels that a.60 -day (2 -month) separation between 'two concurrent
sampling events in a year period (12 months) gives sufficient time to capture two representative
events to fulfill the semi' -annual sampling schedule If significant drought conditions'make
capturing the subsequent qualifying event within the semi-annual (6 month) sampling period
window, the Division will work with permittees who document°that difficulty -in their monitoring
records

DukeEnergy Carolinas, LLC
March 21, 2012
Page 8 of 9
Response to Comments from Duke Energy oh PreVi'ous Draft Permits, cont.
iWa'rsliali Stearn Station - NUJ000S46
Comments on the draft,permit were received July 20, 2011, and subsequent comments were
received via e-mail on November 18,2011. We have tried to address;many of these comments
below.
With its permit application, the company requested;representative outfall status (k05) for two
stormwaterAischarge outfalls. 'The ,Mooresville Regional Officebas recommended approval,of
these -outfalls. The recommendations include approval of ROS for SW003 and SW007.
• SW003 represents outfalls SW001, SW002, SW004, SW012, SW022,,and,SWO23.
• SWO07 represents outfalls SWO06, SW008, SW009, and SW011.
Comments on the draft'include concerns about your representative outfall request not being
adequately addressed in the draft permit or cover letter.
Response: DWQ typically handles representative outfall status (ROS) designation outside ofthe
permit because that status (and the relieffrom monitoring, other outfalls)'is subject to change'if
activities or other circumstances change Otherwise, the permittee would have to gb through the
process of'a permit modification every time ROS changed With our current process, designations
of, and any changes to ROS can be handled more expeditiously -without reopening a permit for
modification The Division will verify ROS approval in the cover letter of the issued permit, unless
the company prefers to include these specifications in, the final permit
Your comments indicated many of the,outfalls are currently inaccessible and there are concerns
about safe and secure access to theses,outfalls,for sampling and monitoring.
Response: Most of the outfalls listed will be represented by other outfalls, with the exception of
SWO07 Outfall SWO07 was requested to by representative and therefore we will require it to be
sampled, in order to represent outfalls,SW006-SW009 and SW011 Attached to the comments was a
photo of SWO07 that noted sample,collection probability was "likely" if sampled upstream of the
Outlet because-it'is submerged This approach is acceptable We understand your concerns about
safety and secure access,to outfalls, and we fully support taking caution in order to make sure
outfalls are accessed safely We encourage sampling at the nearest, safely accessible location
upstream of a stormwater outfall when itis necessary
The company requested requirements for monitoring of SWO09 be removed from the°permit.
Response: The requirement in Part I1, Section B, Table 1, Footnote 3 has been removed given this
outfall will be represented by SW007. 'Please make sure to comply with Part III, Section E.4 of the
permit in case changes in the NPDES Wastewater permitrequire sampling at this outfall.
Earlier responses to Duke Energy's,comments pertaining to Plant Allen address other comments
submitted by the company for Marshall Steam Station.

t .
Puke Energy Carolinas, LLC
March 21, 2012
Page 9 of 9
Response to Comments from Duke Energy on Previous Draft Permits, cont.
Hiverbend Steam Station - M SU00S49
Comments on the draft°permitwere received August 16, 201'1, and subsequent comments were
received via e-mail on November 18, 2011. We.have tried to address many of these comments
below.
With its permit application, the company requested representative outfall status (ROS) for two
stormwater discharge outfalls (SDO) ; SWO02 and SW004. Duke Energy's.comments'in September
2011 reduced chat and requesred KOS for only asingle SDu; SWG02. The Mooresville Regional
Office has recommended approval With some modifications as discussed with you at the site visit
on June 22, 2011 The recommendations include approval of ROS for SWO01; SWO02, and SWO06
(instead of SW004).
• SWO01 represents outfall SW001.
• SWO02 represents outfalls SWO02, SW005, SW007, and SW014.
e SWO06 represents outfalls SW003, SWO06, and SWO08
Based on the site visit, outfalls SW004, SW010, SW011, and SW012'w►11 not be monitored since,they
are not part'of the industrial activities that occur on the site.
D.WQ typically handles representative outfall status (ROS) designation outside of the permit
because that status (and`the relief from monitoring other outfalls) is subject to change if activities
or other circumstances change. Otherwise, the permitte&would have to go through the process of'a
permit modification every time ROS changed. With our current process, designations of, and any
changes to,ROS� can be handled more expeditiously without reopening a permit for modification_.
The Division will verify ROS approval in the cover letter of the issued permit, unless the company
prefers to include these specifications in the final permit
The company commented that several stormwater outfalls are currently inaccessible, and that
there are concerns about safe andsecure access to theses outfalls for sampling and monitoring. For
example, you indicated sampling.from SWO06 and SWQ14 was not feasible.
Response: Most of the outfalls listed will be represented by other outfalls„ with the exception of
SWO06 The Mooresville Regional Office (MRO) has recommended that SWO06 be a representative
outfall; and the,Central Office'is recommending only annual sampling Attached to the comments
was a photo of SWO06 that noted sample collection probability was not feasible at,the outlet
However, �it would be acceptable to sample further;upstream of the pipe outlet for SWO06 We
understand'your concerns about safety and secure access to outfalls, and we fully support taking
caution in order to make sure outfalls are, accessed safely We encourage sampling at the nearest,
safely accessible,location upstream of a stormwater outfall ,when it is necessary
Earlier "responses to Duke Energy's comments pertaining to Plant Allen address other comments
submitted by"the company for Riverbend Steam Station.