NC0003425_Fact Sheet_20170101

EXHIBIT 10
DENR/DWR Fact Sheet for NPDES Development
Riverbend Permit Renewal NC0004961
2015

DENR/DWR
FACT SHEET FOR NPDES PERMIT DEVELOPMENT
PERMIT RENEWAL
NPDES No. NC0004961
Facility Information
Applicant/Facility Name:
Duke Energy Carolinas, LLC — Riverbend Steam Station
Applicant Address:
P.O. Box 1006, Charlotte, North Carolina 28201
Facility Address:
175 Steam Plant Road; Mount Holly, North Carolina 28120
Permitted Flow
No limit
Type of Waste:
100% industrial
Prim.SIC Code: 4911 — Electric Services
Facility/Permit Status:
Class I/Active; Renewal
County:
Gaston County
Miscellaneous
Receiving Stream:
Catawba River
(Mt. Island Lake)
Regional Office:
Mooresville
Stream Classification:
WS-IV and B-CA
State Grid / USGS Quad:
F15Sw
303(d) Listed?
No
Permit Writer:
Sergei Chernikov,
Ph.D.
Subbasin:
03-08-33
Date:
Ma 21, 2014
Drainage Area (mi):
1800
001: Lat. 35° 21' 28" N Long. 80° 58' 12" W
002: Lat. 350 22' 06" N Long. 80' 57' 3 1 " W
002B: Lat. 35021' 51" N Long. 800 58' 11" W
011: Lat. 35° 21' 38" N Long. 80' 58' 38" W
Summer 7Q 10 (cfs)
80
Winter 7Q10 (cfs):
30Q2 (cfs)
Average Flow (cfs):
2700
IWC % for Outfall 002:
( )
0.4 — discharge
g
2.7 —dewatering
SUMMARY
Duke Energy's Riverbend Steam Station was a coal fired steam electric plant in Gaston County,
the electricity generation was discontinued on 04/1/2013. The facility has 5 permitted outfalls in
the current NPDES discharge permit. The sources of wastewater for these outfalls include non -
contact cooling water, ash basin discharge, sanitary waste, stormwater from process areas, sump
overflows, and potentially contaminated groundwater seeps. The facility has no FGD scrubber.
Currently, discharge of cooling water has discontinued and discharge from the ash pond
significantly decreased.
In addition to NPDES Permit NC0004961, the facility also holds 0388R20 (air permit) and
NCD024717423 (Hazardous wastes). The facility is subject to 40 CFR 423 — Steam Electric
Power Generation.
The following descriptions of the wastes at each outfall are offered:
001 — Once through cooling water consisting of intake screen backwash and water from
the plant chiller system, turbine lube oil coolers, condensate coolers, main turbine steam
condensers and the intake tunnel dewatering sump.
Since the facility was shut down, the discharge from this outfall is not anticipated.
Fact Sheet
NPDES NC0004961 Renewal
Page 1

002 — Ash basin discharge consisting of induced draft fan and preheater bearing cooling
water, stormwater from roof drains and paving, treated groundwater, track hopper sump
(groundwater), coal pile runoff, laboratory drain and chemical makeup tanks and drums
rinsate wastes, general plant/trailer sanitary wastewater, turbine and boiler rooms sumps,
vehicle rinse water, and stormwater from pond areas, upgradient watershed, and
miscellaneous stormwater flows. Most of the waste streams have discontinued, but some
will remain.
002A- Yard drain sump overflow, discharge occurs rarely.
010 — Combined flow from all seeps.
011 — Former stormwater Outfall 1. Contains stormwater and groundwater now, also
includes wastewater from 10,000 gallon oil separator tank #3. The drainage basin
includes a 2.7 acre portion of the main switchyard and 8,700 ft2 of the plant yard between
power house and combustion turbine area. The powerhouse covers about 1.5 acres of the
drainage basin. 100% of the drainage basin is paved or roofed.
This facility discharges to the Mountain Island Lake (Catawba River) in sub -basin 03-08-33.
The receiving stream is not listed as impaired.
Duke Energy Submitted Application dated May 15, 2014. The current permit expires February
28, 2015.
Duke Energy is required by the Coal Ash Management Act to remove all ash from the site by
August 1, 2019.
The discharge pipe NPDES outfall 002 from the secondary ash basin discharge tower at
Riverbend Steam Station will be slip lined to ensure integrity. While this pipe is being slip lined,
an alternative arrangement to convey wastewater to the permitted NPDES outfall 002 will be
utilized. Temporary piping will be positioned in the secondary ash basin and the treated
wastewater will be pumped to the NPDES outfall 002 discharge flow weir, located before the
concrete flume that discharges into Mountain Island Lake. Once the slip line repairs are
completed, the system will be returned to its original configuration. NPDES monitoring
requirements will continue to be collected during the slip line project at the NPDES outfall 002
discharge flow weir.
SEEPS-OUTFALL 010
The facility identified 12 unpermitted seeps from the ash settling basin. Seeps can be classified
as either engineered seeps (toe drains) from the earthen dam or non -engineered seeps that occur
as wastewater moves from the ash settling basin into groundwater and then into surface water,
either directly or after emerging on land. Engineered seeps can be captured and routed through a
permitted outfall.
The non -engineered seeps represent a treatment system that has the potential to contaminate
groundwater and surface water. The original design and location of the impoundment are such
that wastewaster is not contained and directed to only engineered outfalls as the NPDES program
generally contemplates, but wastes are also being released to groundwater and emerging in the
form of seeps at the surface at diffuse and remote locations, with wastewater then flowing into
surface waters depending on site specific factors. Potential groundwater contamination is
regulated through North Carolina's 2L program. The CWA NPDES permitting program does not
Fact Sheet
NPDES NC0004961 Renewal
Page 2

normally envision permitting of uncontrolled releases from treatment systems; such releases are
difficult to monitor and control, and it is difficult to accurately predict their impact on water
quality. Releases of this nature would typically be addressed through an enforcement action
requiring their elimination rather than permitting.
The non -engineered seeps at this facility represent a unique circumstance, where the occurrence
of the seeps is attributable to an original pond design that will require long-term action to fully
address. Recent North Carolina legislation (Coal Ash Management Act of 2014) establishes a
framework for addressing all coal ash impoundments in the state to ensure that groundwater and
surface water are adequately protected through closure or other measures. However, action to
close or otherwise address coal ash impoundments and their threats to surface waters and
groundwater will occur over a long term of those actions. In light of the long-term nature of
action to fully address these impoundments, the Division is proposing, as an interim measure, to
ensure that all non -engineered seeps are appropriately identified, monitored, and subject to
protective effluent limits by including the seep discharges as authorized discharges in the
facility's NPDES permit. The permit includes requirements to regularly inspect for new seeps,
monitoring requirements for all identified seeps, and applicable effluent limits which ensure that
the seeps will not result in unacceptable impacts to the receiving stream.
The facility identified 12 unpermitted seeps and conducted chemical analysis of the discharges.
The total flow from the seeps was measured at 0.14 MGD. Although, all seeps don't have a
permanent discharge and discharge from all seeps does not reach the surface water, for the
purposes of the permitting it was assumed that all seeps reach the surface water. The seeps are
not located on the walls of the dike, they appear as an emerging groundwater in a swampy area
adjacent to the lake.
The maximum allowable parameter concentration for seeps was determined by multiplying the
highest concentration for a baseline seep data by 10. These values are substantially lower than
the allowable concentration determined by the Reasonable Potential Analysis for the combined
seep flow. The maximum allowable concentrations for Pb and TDS were established at the level
of the water quality standards.
ASH POND DAMS
Seepage through earthen dams is common and is an expected consequence of impounding water
with an earthen embankment. Even the tightest, best -compacted clays cannot prevent some
water from seeping through them. Seepage is not necessarily an indication that a dam has
structural problems, but should be kept in check through various engineering controls and
regularly monitored for changes in quantity or quality which, over time, may result in dam
failure.
REASONABLE POTENTIAL ANALYSIS
The Division conducted EPA -recommended analyses to determine the reasonable potential for
toxicants to be discharged at levels exceeding water quality standards/EPA criteria by this
facility from outfall 002 (Ash Pond). Calculations included: As, Be, Cd, Total Phenolic
Compounds, Cr, Cu, CN, Pb, Hg, Mo, Ni, Se, Ag, Zn, and Fe (please see attached). The renewal
application listed 0.19 MGD as a current flow. The analysis indicates no reasonable potential to
violate the surface water quality standards or EPA criteria. However, the monitoring will
continue per recommendation of the hearing officer during the last renewal.
The Division also considered data for other parameters of concern in the EPA Form 2C that the
facility submitted for the renewal. The majority of the parameters were not detected in the
Fact Sheet
NPDES NC0004961 Renewal
Page 3

discharge. The Division reviewed the following parameters that were detected in the discharge
and have applicable state standards or EPA criteria for Class C WS-IV stream: fecal coliform,
nitrate, Al, Ba, B, Co, Mn, Sb, and Tl. Most of these parameters were well below the state
standards/EPA criteria. Only 1 parameter exceeded EPA criteria: Al (162 ug/L is above 87 ug/L).
Considering the in -stream waste concentration of only 0.4%, even Al is not expected to violate
applicable water quality criterion.
The RPA was also conducted for the combined flow from all the seeps. The highest
concentration for each constituent was chosen from one of the 12 seeps and used for the RPA.
The RPA was not considered for the parameters that don't have an applicable state water quality
standard. Calculations included: As, Cd, Chlorides, Cr, Cu, F, Pb, Hg, Ni, Se, Zn, Ba, Fe, and
Mn (please see attached). The analysis indicates no reasonable potential to violate the water
quality standards or EPA criteria. The combined flow volume for all the seeps was measured at
0.14 MGD. However, the flow of 0.5 MGD was used for the RPA to incorporate a safety factor,
account for potential new seeps that might emerge in the future or increase in flow volume at the
existing seeps.
The RPA was also conducted for the Outfall 011. Calculations included: As, Cd, Chlorides, Cr,
Cu, F, Pb, Hg, Ni, Se, Zn, Ba, Fe, and Mn (please see attached). The analysis indicates no
reasonable potential to violate the water quality standards or EPA criteria. The flow volume for
the Outfall 011 was measured at 0.00036 MGD. However, the flow of 0.001 MGD was used for
the RPA to incorporate a safety factor and potential increase in flow.
The RPA analysis indicates that existing discharges from the facility outfalls will not cause
contravention of the state water quality standards/ EPA criteria.
DEWATERING — OUTFALL 002
To meet the requirements of the Coal Ash Management Act of 2014, the facility needs to
dewater two ash ponds and excavate the ash to deposit it in the landfills. The facility highest
discharge rate from the dewatering process will be 1.45 MGD. The facility submitted data for the
surface water in the ash ponds, interstitial water in the ash, and interstitial ash water that was
treated by 20 µm filter and 0.45 µm filter. To evaluate the impact of the dewatering on the
receiving stream the RPA was conducted for the wastewater that will be generated by the
dewatering process. To introduce the margin of safety, the highest measured concentration for a
particular parameter was used. The RPA was conducted for As, Cd, Chlorides, Cr, Cu, F, Pb,
Mo, Hg, Ni, Se, Zn, Ba, Fe, and Mn, SO4, Al, B, Sb, and Tl (please see attached).
Based on the results of the RPA, the limit for Total Aluminum will be added to the dewatering
effluent page.
TECHNOLOGY BASED EFFLUENT LIMITS OUTFALL002 AND OUTFALL 010
The existing federal regulations require development of Technology Based Effluent Limits
(TBELs) for the parameters of concern. Since the EPA has not promulgated any new Effluent
Guidelines for Power Plants since 1982, the Division has reviewed the performance of the
existing coal-fired power plants to establish TBELs: Marshall Steam Station, Belews Steam
Station, and Allen Steam Station. Two of these facilities (Belews and Allen) were used by EPA
to establish the proposed Effluent Guidelines for Power Plants. The Division focused on the
following parameters: Total Arsenic, Total Mercury, Total Selenium, and Nitrate/nitrite as N.
These parameters are consistent with the parameters selected by EPA in the proposed Effluent
Guidelines. The Division agrees with the EPA statement from the proposed Effluent Guidelines
Fact Sheet
NPDES NC0004961 Renewal
Page 4

that justifies TBEL limitations for only four pollutants of concern: "Effluent limits and
monitoring for all pollutants of concern is not necessary to ensure that the pollutants are
adequately controlled because many of the pollutants originate from similar sources, have similar
treatabilities, and are removed by similar mechanisms. Because of this, it may be sufficient to
establish effluent limits for one pollutant as a surrogate or indicator pollutant that ensures the
removal of other pollutants of concern."
Based on the review of the effluent data for the past 5 years the Division established the
following TBELs for the coal-fired power plants in North Carolina. The monthly average limits
for Total Arsenic and Total Selenium are based on 95th percentile of the effluent data, which is
consistent with the EPA methodology, and daily maximum limits for these constituents are based
on the 99.9th percentile of the effluent data. The Total Mercury limit is based on the Statewide
Mercury TMDL implementation strategy and was established by the Division previously.
Total Arsenic — 10.5 µg/L (Monthly Average); 14.5 µg/L (Daily Maximum)
Total Selenium — 13.6 µg/L (Monthly Average); 25.5 µg/L (Daily Maximum)
Total Mercury — 47.0 ng/L (Monthly Average); 47.0 ng/L (Daily Maximum)
The Division does not have any long-term data for Nitrate/nitrate as N. Therefore, the limits for
this parameter are based on the proposed EPA Effluent Guidelines.
Nitrate/nitrite as N — 0.13 mg/L (Monthly Average); 0.17 mg/L (Daily Maximum)
Facility is allowed 4.5 years from the effective date of the permit to comply with the TBELs
(Outfall 002 only —Ash Pond Discharge). This time period is provided in order for the facility to
budget, design, and construct the treatment system. The compliance schedule is consistent with
the proposed EPA Effluent Guidelines that require compliance with the TBELs "as soon as
possible within the next permit cycle beginning July 1, 2012". Since the permit cycle is 5 years,
the Effluent Guidelines will allow the facility to comply with the TBELs by June 30, 2022. This
permit has a more stringent requirements, the facility shall comply with the TBELs by the end of
2019.
In the interim, the facility shall comply with the BPJ temporary limits that are derived by
multiplying the proposed TBELs by 5, please see below:
Total Arsenic — 52.5 µg/L (Monthly Average); 72.5 µg/L (Daily Maximum)
Total Selenium — 68.0 µg/L (Monthly Average); 127.5 µg/L (Daily Maximum)
Nitrate/nitrite as N — 0.65 mg/L (Monthly Average); 0.85 mg/L (Daily Maximum)
Although these interim limits higher than the proposed TBELs, they are significantly lower than
the allowable concentrations determined by the Reasonable Potential Analysis (RPA) and
should be protective of the water quality in the receiving stream. The RPA allowable
concentrations are listed below:
Total Arsenic—13,632.3 µg/L (Monthly Average); 91,690.8 µg/L (Daily Maximum)
Total Selenium — 1,363.2 µg/L (Monthly Average); 12,492.0 µg/L (Daily Maximum)
TEMPERATURE VARIANCE REMOVAL-OUTFALL 001
The facility historically had a temperature variance in accordance with CWA Section 316(a). In
order to maintain the variance the facility had to conduct annual biological and chemical
monitoring of the receiving stream to demonstrate that it has a balanced and indigenous
Fact Sheet
NPDES NC0004961 Renewal
Page 5

macroinvertebrate and fish community. The latest BIP (balanced and indigenous population)
report was submitted to DWQ in August of 2009. The ESS has reviewed the report and
concluded that the Mountain Island Lake near Riverbend Station has a balanced and indigenous
macroinvertebrate and fish community.
Since the facility discontinued electricity generation in 2013, it does not wish to request
continuation of the temperature variance. Therefore, Effluent Sheet A. (L) was modified to
reflect temperature requirements without a variance.
CWA SECTION 316(B)
Since the facility discontinued electricity generation in 2013 and does not use cooling water, it
will not be the subject to the Section 316(b) of Clean Water Act.
INSTREAM MONITORING-OUTFALL 002
The facility historically had 7 monitoring station, 2 located upstream and 5 located downstream.
It is recommended that the monitoring will continue.
The permit also required semi-annual upstream and downstream monitoring of the ash pond
discharge. Upstream site (Station B) is approximately 2 miles upstream of the discharge and
downstream location (Station C) is approximately 0.5 miles downstream of the discharge. These
monitoring stations have been established through the BIP monitoring program, which was
required to maintain 316(a) temperature variance. The monitored parameters are: As, Cd, Cr, Cu,
Hg, Pb, Se, Zn, and Total Dissolved Solids (TDS). The majority of the results are below
detection level, the rest of the results are below water quality standards. These results are
consistent with the previous monitoring results.
It is required that the monitoring at the stations B and C will continue until discharges from the
station are ceased. It is also required that the facility uses low level method 1631E for all Hg
analysis.
FISH TISSUE MONITORING-OUTFALL 002
The permit required fish tissue monitoring for As, Se, and Hg near the ash pond discharge once
every 5 years. This frequency is consistent with EPA guidance. Sunfish and bass tissues were
analyzed for these trace elements. The results were below action levels for Se and Hg (10.0 µg/g
— Se, 0.40 µg/g — Hg, NC) and screening value for As (1.20 — µg/g, EPA). These results are
consistent with the previous monitoring results.
TOXICITY TESTING- Outfall 002:
Current Requirement: 24hr Chronic P/F @ 10%
Recommended Requirement: 24hr Chronic P/F @ 2.7% (flow during dewatering)
Monitoring Schedule: January, April, July, October
This facility has passed all chronic toxicity tests during the previous permit cycle, please see
attached. The change is the instream waste concentration was made based on the significant
decrease in the discharge volume.
COMPLIANCE SUMMARY
Notwithstanding the civil lawsuit filed for unauthorized discharges and groundwater
exceedances/violations, based on the monitoring required under the current version of the permit
there were no violations of effluent standards contained in the permit.
Fact Sheet
NPDES NC0004961 Renewal
Page 6

PERMIT LIMITS DEVELOPMENT
• The pH limits (Outfalls 002, 002A, and 010) in the permit are based on the North
Carolina water quality standards (15A NCAC 2B .0200).
• The limits for Oil and Grease and Total Suspended Solids (Outfall 002 and Outfall 002A)
are based on the Best Professional Judgment and are lower than prescribed in the 40 CFR
423.
• The limits for Total Copper and Total Iron (Outfall 002 and Outfall 002A) were
established in accordance with the 40 CFR 423.
• The temperature limits (Outfall 001) are based on the North Carolina water quality
standards (15A NCAC 2B .0200).
• The turbidity limit in the permit (Outfall 002) is based on the North Carolina water
quality standards (15A NCAC 2B .0200).
• The Technology Based Effluent Limits (Outfall 002 and Outfall 010) for Total Arsenic,
Total Mercury, Total Selenium, and Nitrate/nitrate as N are based on the requirements of
40 CFR 125.3(a) , 40 CFR 122.44(a)(1); 125.3(c) and (d).
• The Interim Technology Based Effluent Limits (Outfall 002) for Total Arsenic, Total
Selenium, and Nitrate/nitrate as N are based on the requirements of 40 CFR 125.3(a) , 40
CFR 122.44(a)(1); 125.3(c) and (d).
• The Whole Effluent Toxicity limit (Outfall 002) is based on the requirements of 15A
NCAC 213.0500.
• The Total Aluminum limits (Outfall 002 dewatering) in the permit are based on the
results of the statistical analysis of the interstitial water data.
REQUESTED MODIFICATIONS
With the permit application for renewal, Duke Energy Carolinas, LLC has requested the
following modifications:
Monitoring Frequencies (Outfall 002)
Parameter
Present
Proposed
Flow
Weekly
Monthly
Total Nitrogen
2/year
1/year
Total Phosphorus
2/year
1/year
Total Copper
Quarterly
none
Total Iron
Quarterly
none
These requests could not be granted because the Division needs these data to assure compliance
with the water quality standards and criteria during the upcoming ash pond decanting/dewatering
process.
PROPOSED CHANGES:
• Monitoring requirements for Outfall 001 were adjusted due to the discontinuation of
once -through cooling water discharges.
• The Ash Pond Closure Special Condition was updated (Please see A. (15.)).
• The Seep Outfall 010 (Please see A. (5)) and Seep Pollutant Analysis Special Condition
(Please see A. (17.)) were added to the permit.
• The Appendix A and Appendix B were added to the permit.
• A separate effluent page for the dewatering of the ash ponds (Outfall 002) was added to
the permit (Please see Special Condition A. (3)).
• The Boiler Cleaning Waste Special Condition was eliminated due to the discontinuation
of the power generation.
Fact Sheet
NPDES NC0004961 Renewal
Page 7

• The Section 316(a) of CWA Thermal Variance Special Condition was eliminated due to
the discontinuation of the power generation.
• The Section 316(b) of CWA Special Condition was eliminated due to the discontinuation
of the power generation.
• The turbidity limit was added to the permit to meet the state turbidity standard per 15A
NCAC 2B .0211(3) (k) (Outfall 002).
• The Technology Based Effluent Limits for Total Arsenic, Total Mercury, Total Selenium,
and Nitrate/nitrite as N were added to the permit and are based on the requirements of 40
CFR 125.3(a) , 40 CFR 122.44(a)(1); 40 CFR 125.3(c) and (d) (Outfall 002 and Outfall
010).
• The Interim Technology Based Effluent Limits (Outfall 002) for Total Arsenic, Total
Selenium, and Nitrate/nitrate as N were added to the permit and are based on the
requirements of 40 CFR 125.3(a) , 40 CFR 122.44(a)(1); 125.3(c) and (d).
• Proposed federal regulations require electronic submittal of all discharge monitoring
reports (DMRs) and specify that, if a state does not establish a system to receive such
submittals, then permittees must submit DMRs electronically to the Environmental
Protection Agency (EPA). The Division anticipates that these regulations will be adopted
and is beginning implementation.
The requirement to begin reporting discharge monitoring data electronically using the NC
DWR's Electronic Discharge Monitoring Report (eDMR) internet application has been
added to the permit. (Please see Special Condition A. (18.)).
• The Applicable State Law Special Condition was added to the permit to meet the
requirements of Senate Bill 729 (Coal Ash Management Act, Please see Special
Condition A. (19.)).
• The Outfall 011 (former Stormwater Outfall 1) was added to the permit (Please see A.
(20.)).
PROPOSED SCHEDULE:
Draft Permit to Public Notice: March 6, 2015 (est.)
Permit Scheduled to Issue: July 27, 2015 (est.)
STATE CONTACT:
If you have any questions on any of the above information or on the attached permit, please
contact Sergei Chernikov at [phone] or [e-mail]
Fact Sheet
NPDES NC0004961 Renewal
Page 8