HomeMy WebLinkAboutNCS000549_Draft Permit Fact Sheet_20150305Fact Sheet
NPDES Stormwater Permit NCS000549
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DENR/DEMLR
FACT SHEET FOR NPDES STORMWATER PERMIT DEVELOPMENT
NPDES No. NCS000549
Facility Information
Applicant/Facility Name: Duke Energy Carolinas, LLC – Riverbend Steam Station
Applicant Address: P.O. Box 1006, Mail Code EC13K; Charlotte, North Carolina 28201
Facility Address: 175 Steam Plant Road; Mount Holly, North Carolina 28120
Permitted Flow: N/A (Stormwater Discharges Only)
Industrial Activities: Primary SIC Code: 4911 – Electric Services
Permit Status: New NPDES Stormwater Permit
County: Gaston County
Miscellaneous
Receiving Stream: Catawba River
(Mt. Island Lake)
Regional Office: Mooresville
Stream Classification: WS-IV and B State Grid / USGS Quad: F15Sw
303(d) Listed? Hg, statewide Permit Writer: B. Georgoulias
Subbasin: 03-08-33 Date: March 5, 2015
Facility Location: Lat. 35 21’ 40” N Long. 80 58’ 32” W
BACKGROUND
Duke Energy’s Riverbend Steam Station was a coal fired steam electric plant in Gaston County.
Electricity generation was discontinued on April 1, 2013. One stormwater outfall has been
abandoned (SW009), and SW013 will be grouted and abandoned (per info. submitted by company
on December 15, 2014); SW007 and an outfall west of SW007 are scheduled to be removed. During
a site visit in June 2013, Stormwater Permitting Program (SPP) staff determined that SW005 was
not a potential point source discharge regulated under NPDES. Some outfalls were not included in
the original application and are described as “unidentified outfalls” in the draft permit.
In addition to NPDES wastewater discharge permit NC0004961, the facility also holds 0388R20 (air
permit) and NCD024717423 (Hazardous wastes). The facility is subject to federal requirements of
40 CFR §423 – Steam Electric Power Generation. This category is subject to federal NPDES
stormwater discharge permit requirements per 40 CFR §122.26 (b)(14)(vii).
The company originally applied to the Stormwater Permitting Program (SPP) for a separate NPDES
stormwater discharge permit for this facility in May 2011. A draft permit was proposed and sent to
public notice in July 2011. A subsequent revised draft went to the company in March 2012 but was
never re-noticed or finalized. On May 15, 2014, in response to NCDENR actions following the coal
ash spill at Dan River in Eden, NC earlier that year, the company submitted materials to revise
information in the original application. The new proposed draft permit is based on more recent site
activity information, sampling results, and visits by NCDENR staff.
This facility discharges to the Catawba River (Mountain Island Lake), upstream of Lake Wylie.
Mountain Island Lake is not impaired, but dischargers upstream of Lake Wylie are subject to the
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NPDES Stormwater Permit NCS000549
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nutrient management strategy developed for that watershed (Lake Wylie TMDL, 1995). There is
also a statewide total maximum daily load (TMDL) for mercury (Hg), approved in September 2012.
No specific reductions or Hg limits are required from NPDES stormwater permittees at this time.
Duke Energy has developed a decommissioning plan for ash ponds on the site, submitted to the
Division of Water Resources (DWR) at the end of 2014.
The facility historically had a temperature variance for its NPDES wastewater discharge permit. 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 macroinvertebrate and fish
community. The latest BIPA (Balanced and Indigenous Population Assessment) report was
submitted to DWQ (now DWR) in August of 2009. The Environmental Sciences Section (ESS)
reviewed the report and concluded that Mountain Island Lake near Riverbend Station has a
balanced and indigenous macroinvertebrate and fish community.
WHY THIS FACILITY IS SUBJECT TO A PERMIT
Federal NPDES regulations define stormwater discharge associated with industrial activity in
40 CFR §122.26 (b)(14) as:
“the discharge from any conveyance that is used for collecting and conveying storm water
and that is directly related to manufacturing, processing or raw materials storage areas at
an industrial plant. The term does not include discharges from facilities or activities
excluded from the NPDES program under this part 122. For the categories of industries
identified in this section, the term includes, but is not limited to, storm water [sic]
discharges from industrial plant yards; immediate access roads and rail lines used or
traveled by carriers of raw materials, manufactured products, waste material, or by-
products used or created by the facility; material handling sites; refuse sites; sites used for
the application or disposal of process waste waters (as defined at part 401 of this chapter);
sites used for the storage and maintenance of material handling equipment; sites used for
residual treatment, storage, or disposal; shipping and receiving areas; manufacturing
buildings; storage areas (including tank farms) for raw materials, and intermediate and
final products; and areas where industrial activity has taken place in the past and
significant materials remain and are exposed to storm water. For the purposes of this
paragraph, material handling activities include storage, loading and unloading,
transportation, or conveyance of any raw material, intermediate product, final product, by-
product or waste product. The term excludes areas located on plant lands separate from
the plant's industrial activities, such as office buildings and accompanying parking lots as
long as the drainage from the excluded areas is not mixed with storm water [sic] drained
from the above described areas.”
Although electricity generation at Riverbend has ceased, coal ash and other materials are still
present at the site. Concentrations of copper, zinc, mercury, and selenium from SW001 and SW002
discharges already dropped significantly after the company cleaned out oil trap tanks controlling
these areas (see May 2014 and July 2014 sample results). Coal ash will likely be disturbed and/or
transported as ash pond close-out procedures are carried out. Equipment decommissioning and
deconstruction activities will disturb areas with potential to release contaminants.
PROPOSED MONITORING FOR STORMWATER DISCHARGES
The Division considered potential pollutants from past and present industrial activities (coal-fired
electric generation, plant decommissioning, and future ash removal) and data submitted in both
May 2011 (collected June 2008) and in May 2014 (collected the same month). Sampling included
O&G, COD, Cl, Fl, SO4, Hg, Al, As, Ba, B, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Se, Sb, Tl, Zn, TDS, TSS,
conductivity, and pH. In 2008, Ag, Co, Ti, BOD, ammonia, TN, TP, and phenol were also sampled.
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NPDES Stormwater Permit NCS000549
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Sampling results were submitted with EPA Form 2F as part of the NPDES stormwater permit
application in 2014. Outfalls SW001 and SW002 were resampled in June and July 2014. See
attached information for sampling results. SW001 currently includes a non-stormwater discharge
(likely groundwater), which may be permitted separately under the wastewater permit for this
facility.
Unlike most stormwater permits in its program, the Division is proposing a permit structure with
outfall-specific monitoring for discharges. Parameters are based on potential pollutants in the
drainage area, sampling results, and in some cases, dependent upon future activities (e.g., ash
removal through the drainage area). Below is a table of the proposed monitoring for each outfall at
the Riverbend site. All outfalls ultimately discharge to the Catawba River (Mountain Island
Lake).
Stormwater Discharge Outfall (SDO) Monitoring
SW001, SW002, SW003
Draining powerhouse and switchyard areas
Polychlorinated Biphenyls
(PCBs)
Monitored semi-annually; may be discontinued after the first year
(two samples) if not detected. BASIS: Electrical equipment in
these drainage areas (powerhouse and switchyard areas) may have
contained PCBs, which persist in the environment if ever released.
(An empty Used PCB Mineral Oil Storage Tank elsewhere on the
property stored this material at one time.) If all PCBs have been
removed and past releases cleaned up, these compounds should not
be detected.
Copper Semi-annual monitoring. BASIS: Coal combustion waste (CCW)
constituent; very high concentrations measured in discharge from
SW001 and SW002 in 2008 and 2014 (order of magnitude above
stormwater benchmark value based on acute impacts). Discharge
concentrations were also significantly higher than up and
downstream values in the lake between 2011-2014 (<2 g/l), as
reported in the NPDES WW permit application.
Selenium Semi-annual monitoring. BASIS: Coal combustion waste (CCW)
constituent; concentrations above stormwater benchmark measured
in discharge from SW001 and SW002 in 2008 and 2014.
Mercury Semi-annual monitoring with Method 1631E. BASIS: Coal
combustion waste (CCW) constituent; 60 ng/l concentration
recorded from SW001 in 2014 (above the quantitation level (QL) of
EPA Method 245.1, much less sensitive than low level method
1631E). Other results for these outfalls were reported <50 ng/l. The
low-level Hg method provides the lowest minimum level of EPA
approved analytical methods for this parameter and will be able to
quantify levels below 50 ng/l (sufficiently sensitive test procedure,
consistent with recent modifications to federal rule 40 CFR §122.44).
Zinc Semi-annual monitoring. BASIS: Coal combustion waste (CCW)
constituent; very high concentrations measured in discharge from
SW001 and SW002 in 2008 and 2014 (order of magnitude above
stormwater benchmark value based on acute threshold). Discharge
concentrations were also significantly higher than up and
downstream values in the lake between 2011-2014 (<2 g/l), as
reported in the NPDES WW permit application.
Total Suspended Solids (TSS) Semi-annual monitoring. BASIS: Potential pollutant from drainage
area and BMP effectiveness indicator. SW001 and SW002 had
highest values of all SDOs on site in 2014 sampling.
Non-polar Oil & Grease (Method
1664 SGT-HEM)
Semi-annual monitoring. BASIS: Potential pollutant from
lubricants; Method 1664 SGT-HEM targets petroleum-based O&G.
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Stormwater Discharge Outfall (SDO) Monitoring
pH Semi-annual monitoring. BASIS: Pollutant indicator and important
to interpreting toxicity potential of metals.
SW004
Draining Horseshoe Bend Beach Road access road area
Total Suspended Solids (TSS) Semi-annual monitoring (quarterly if coal or ash transport). BASIS:
Potential pollutant from drainage area and BMP effectiveness
indicator. This outfall will be impacted by Phase I of the Coal Ash
Excavation Plan (hauling ash from Ash Stack).
Priority Pollutant Metals Ag, As,
Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se,
Tl, and Zn.
Quarterly monitoring only if coal or coal ash transported through
this drainage area. BASIS: Coal combustion waste (CCW)
constituents; includes metals incorporated into the coal ash monofill
constructed for the company’s Mayo Steam Electric Plant (another
site). Monitoring is quarterly because this outfall will be impacted
by Phase I of the Coal Ash Excavation Plan.
Boron Quarterly monitoring only if coal or coal ash transported through
this drainage area. BASIS: Coal combustion waste (CCW)
constituent / coal tracer. Monitoring is quarterly because this outfall
will be impacted by Phase I of the Coal Ash Excavation Plan.
pH Quarterly monitoring only if coal or coal ash transported through
this drainage area. BASIS: Pollutant indicator and important to
interpreting toxicity potential of metals. Monitoring is quarterly
because this outfall will be impacted by Phase I of the Coal Ash
Excavation Plan.
SW005 (near entrance of Horseshoe Bend Beach Road)
Not a point source discharge of stormwater, as observed by SPP staff during June 20, 2014 site visit.
SW003A, the previously unidentified outfall between SW003 and SW006*
*Additional Information about this outfall was requested from the applicant on June 26, 2014. Proposed
parameters may be modified based on details provided.
Total Suspended Solids (TSS) Semi-annual monitoring. BASIS: Potential pollutant from drainage
area and BMP effectiveness indicator.
Non-polar Oil & Grease (1664
SGT-HEM)
Semi-annual monitoring. BASIS: Potential pollutant from
lubricants; Method 1664 SGT-HEM targets petroleum-based O&G.
Priority Pollutant Metals Ag, As,
Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se,
Tl, and Zn.
Semi-annual monitoring. BASIS: Coal combustion waste (CCW)
constituents; includes metals incorporated into the coal ash monofill
constructed for the company’s Mayo Steam Electric Plant.
Boron Semi-annual monitoring. BASIS: Coal combustion waste (CCW)
constituent / coal tracer.
pH Semi-annual monitoring. BASIS: Pollutant indicator and important
to interpreting toxicity potential of metals.
SW006
Drains station yard areas and main fuel oil storage tank area
Polychlorinated Biphenyls
(PCBs)
Monitored semi-annually; may be discontinued after the first year
(two samples) if not detected. BASIS: Electrical equipment in this
drainage area may have contained PCBs, which persist in the
environment if ever released. (An empty Used PCB Mineral Oil
Storage Tank elsewhere on the property stored this material at one
time.) If all PCBs have been removed and past releases cleaned up,
these compounds should not be detected.
Total Suspended Solids (TSS) Semi-annual monitoring. BASIS: Potential pollutant from drainage
area and BMP effectiveness indicator.
Non-polar Oil & Grease (1664
SGT-HEM)
Semi-annual monitoring. BASIS: Potential pollutant from
lubricants; Method 1664 SGT-HEM targets petroleum-based O&G.
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Stormwater Discharge Outfall (SDO) Monitoring
pH Semi-annual monitoring. BASIS: Pollutant indicator.
SW007 and SW007A, the previously unidentified outfall west of SW007*
*Additional Information about this outfall was requested from the applicant on June 26, 2014. Both of these
outfalls are scheduled to be removed by the applicant and may not be included in the final permit.
Total Suspended Solids (TSS) Semi-annual monitoring. BASIS: Potential pollutant from drainage
area and BMP effectiveness indicator.
Priority Pollutant Metals Ag, As,
Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se,
Tl, and Zn.
Semi-annual monitoring only if coal or coal ash transported through
this drainage area. BASIS: Coal combustion waste (CCW)
constituents; includes metals incorporated into the coal ash monofill
constructed for the company’s Mayo Steam Electric Plant.
Boron Semi-annual monitoring only if coal or coal ash transported through
this drainage area. BASIS: Coal combustion waste (CCW)
constituent / coal tracer.
pH Semi-annual monitoring only if coal or coal ash transported through
this drainage area. BASIS: Pollutant indicator and important to
interpreting toxicity potential of metals.
SW008
Draining all areas that drain to the cinder pit
Monitoring only required if discharges occur from storm events less than
the 25-year, 24-hour storm (5.7”)
Total Suspended Solids (TSS) Semi-annual monitoring (if applicable). BASIS: Potential pollutant
from drainage area and BMP effectiveness indicator.
Priority Pollutant Metals Ag, As,
Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se,
Tl, and Zn.
Semi-annual monitoring (if applicable). BASIS: Coal combustion
waste (CCW) constituents; includes metals incorporated into the coal
ash monofill constructed for the company’s Mayo Steam Electric
Plant.
Boron Semi-annual monitoring (if applicable). BASIS: Coal combustion
waste (CCW) constituent / coal tracer.
pH Semi-annual monitoring (if applicable). BASIS: Pollutant indicator
and important to interpreting toxicity potential of metals.
SW010, SW011, SW012
Draining areas from the Lark Maintenance Facility
Copper Semi-annual monitoring. BASIS: Potential pollutant from
maintenance facility; 2014 sampling results showed high Cu values
from SW010 and SW011.
Zinc Semi-annual monitoring. BASIS: Potential pollutant from
maintenance facility; 2014 sampling results showed high Zn values
from all three of these outfalls.
Total Suspended Solids (TSS) Semi-annual monitoring. BASIS: Potential pollutant from
maintenance facility and BMP effectiveness indicator.
Non-polar Oil & Grease (1664
SGT-HEM)
Semi-annual monitoring. BASIS: Potential pollutant from
lubricants; Method 1664 SGT-HEM targets petroleum-based O&G.
pH Semi-annual monitoring. BASIS: Pollutant indicator and important
to interpreting toxicity potential of metals; low pH (5.37) recorded
from SW012 in May 2014 sample.
SW014 and other previously unidentified outfalls SW014A, SW014B, etc.
from PVC pipes in Septic Tank Drainage Area*
*Additional Information about this outfall was requested from the applicant on June 26, 2014. Proposed
parameters may be modified based on details provided.
SW014 only No analytical monitoring proposed. BASIS: Limited potential for
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Stormwater Discharge Outfall (SDO) Monitoring
exposure. Septic tank overflow sealed and system receives minimal
flow from so few employees on site. Also a small drainage area
(<900 sq. feet) and no other industrial activities.
Total Suspended Solids (TSS) Semi-annual monitoring at PVC pipe outfall(s) only. BASIS:
Potential pollutant from drainage area and BMP effectiveness
indicator; no information provided about what this outfall drains.
Non-polar Oil & Grease (1664
SGT-HEM)
Semi-annual monitoring at PVC pipe outfall(s) only. BASIS:
Potential pollutant from lubricants; no information provided about
what this outfall drains.
pH Semi-annual monitoring at PVC pipe outfall(s) only. BASIS:
Pollutant indicator; no information provided about what this outfall
drains.
SPECIAL PROVISION FOR SW008 (CLOSED DRY ASH STACK AND CINDER PIT)
The company’s application indicated that SW008 (drainage from the ash stack into the cinder pit)
rarely discharges. The heavily vegetated cinder pit area basically functions as a large dry detention
pond, and water levels rarely build up to the CMP riser pipe that leads to the discharge outlet pipe.
The draft permit proposes monitoring for this outfall only if a discharge results from a storm event
less than the 25-year, 24-hour storm (approximately 5.7” inches in this area of NC, based on NOAA
Precipitation Frequency Estimates). In the industrial stormwater permitting program, NCDEMLR
considers holding ponds that do not discharge in response to smaller storms as equivalent to a non-
discharging system (on the basis that more conservative design specifications for engineered non-
discharge systems use that same design storm criterion). The proposed permit condition is
consistent with that interpretation.
STORMWATER BENCHMARKS AND TIERED RESPONSE
Rather than limits, North Carolina NPDES Stormwater permits contain benchmark concentrations.
Stormwater benchmarks are numerical action levels for stormwater monitoring. Benchmarks are
not effluent limits, and benchmark exceedances are not permit violations. Benchmarks
provide facilities a tool for assessing the significance of pollutants in stormwater discharges and the
effectiveness of best management practices (BMPs). Benchmark concentrations are intended as
guidelines for the facility’s development and implementation of the Stormwater Pollution
Prevention Plan (SPPP).
Benchmark exceedances require the permittee to increase monitoring, increase management
actions, increase record keeping, and/or install stormwater BMPs in a tiered program. The permit
establishes a tiered approach to specify actions the permittee must take in response to analytical
results above benchmark concentrations (Part II, Section B., following Table 10). The tiered
structure of the permit provides the permittee and NCDEMLR wide flexibility to address issues that
may arise with one or more parameters and/or outfalls.
Metals benchmarks are calculated to mimic acute water quality standards and with the guidance of
NC’s Division of Water Resources (DWR). NC DWR follows established federal procedures for
calculating acute standards when developing the benchmarks. Just like the acute standards, metals
benchmarks normally reflect one half of the calculated Final Acute Value (the “½ FAV”). In most
cases, translation into total recoverable values is based on an assumed hardness of 25 mg/l and a
total suspended solids (TSS) concentration of 10 mg/l. Acute standards protect aquatic life from
negative impacts of short-term exposure to higher levels of chemicals where the discharge enters a
waterbody. The Stormwater Permitting Program applies this approach because of the ephemeral
nature of rainfall events.
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The Division may evaluate results to determine if a smaller suite of parameters for some outfalls is
adequate to characterize potential pollution or BMP effectiveness. For example, one or more metals
or other parameters may serve as an adequate tracer for the presence of ash pollution during
disturbance or ash removal in specific drainage areas at this site. For parameters that do not have a
stormwater benchmark, the Division may develop a benchmark value if appropriate toxicity data
become available or if rising trends in concentrations suggest a persistent source.
A summary of the benchmarks in the draft permit, and their basis, is below:
Parameter Benchmark Basis
Antimony (Sb), mg/L (Total) 0.09 Acute Aquatic Criterion, ½ FAV
Arsenic (As), mg/L (Total) 0.34 Acute Aquatic Criterion, ½ FAV
Beryllium (Be), mg/L (Total) 0.065 Acute Aquatic Criterion, ½ FAV
Cadmium (Cd), mg/L (Total) 0.003 Acute Aquatic Criterion, ½ FAV
Chromium (Cr), mg/L (Total) 0.9
½ FAV, based on (Cr III + Cr VI) acute thresholds
and assumption that industrial activities here are
not a source of hexavalent chromium.
Copper (Cu), mg/L (Total) 0.010 Acute Aquatic Criterion, ½ FAV
Lead (Pb), mg/L (Total) 0.075 Acute Aquatic Criterion, ½ FAV
Mercury (Hg), ng/L (Total) N/A
Monitoring only, CCW/Coal Constituent. Hg
influenced by regional transport and wet
deposition. Values above 12 ng/L (NC WQ
standard) should be noted on the DMR but do not
trigger Tier Responses.
Nickel (Ni), mg/L (Total) 0.335 Acute Aquatic Criterion, ½ FAV
Polychlorinated biphenyl
compounds (PCBs), g/L Detected NC Water Quality Standards vs. present Arochlors
quantitation levels (higher than standard)
Selenium (Se), mg/L (Total) 0.056 ½ FAV, NC-specific, based on 1986 Study on Se
impacts in North Carolina
Silver (Ag), mg/L (Total) 0.0003
Acute Aquatic Criterion, ½ FAV. (The Division
notes this value is below the practical quantitation
level (PQL) of 1 g/L of EPA Method 200.8)
Boron (B), mg/L N/A Monitoring only, CCW/Coal Constituent. Narrative
National Recommended Water Quality Criterion.
Thallium (Tl), mg/L (Total) N/A Monitoring Only, CCW/Coal constituent. National
Recommended Human Health Criterion.
Zinc (Zn), mg/L (Total) 0.126 Acute Aquatic Criterion, ½ FAV
Total Suspended Solids (TSS),
mg/L 100 National Urban Runoff Program (NURP) Study,
1983
Non‐Polar Oil & Grease, EPA
Method 1664 (SGT-HEM),
mg/L 15
Review of other state’s daily maximum benchmark
concentration for this more targeted O&G; NC WQ
Standard that does not allow oil sheen in waters.
pH 6-9 NC Water Quality Standard (Range)
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STORMWATER POLLUTION PREVENTION PLAN
The proposed permit conditions reflect the Environmental Protection Agency’s (EPA) and North
Carolina’s pollution prevention approach to stormwater permitting. The Division’s maintains that
implementation of Best Management Practices (BMPs) and traditional stormwater management
practices that control the source of pollutants meets the definition of Best Available Technology
(BAT) and Best Conventional Pollutant Control Technology (BCT). The permit conditions are not
numeric effluent limitations but are designed to be flexible requirements for implementing site-
specific plans to minimize and control pollutants in stormwater discharges associated with the
industrial activity. Title 40 Code of Federal Regulations (CFR) §122.44(k)(2) authorizes the use of
BMPs in lieu of numeric effluent limitations in NPDES permits when the agency finds
numeric effluent limitations to be infeasible. The agency may also impose BMP requirements
which are "reasonably necessary" to carry out the purposes of the Act under the authority of 40
CFR 122.44(k)(3). The conditions proposed in this draft permit are included under the authority of
both of these regulatory provisions. In essence, the pollution prevention and BMP requirements
operate as limitations on effluent discharges that reflect the application of BAT/BCT.
The permit proposes some language specific to coal fired power plants (and in particular, to those
plants being decommissioned). Determining specific BMPs that are appropriate for the site and
activities are the permittee’s responsibility, and the permit strives not to limit what BMPs can be
used. The permittee should also refer to the BMPs described in both EPA’s Multi-Sector Permit
(MSGP) and Industrial Stormwater Fact Sheet for Steam Electric Power Generating Facilities (Sector
O) for guidance on pollution prevention measures.
It is important to note that the majority of stormwater at this facility is ultimately routed into the
waste treatment system (ash pond), and those discharges are regulated by the NPDES wastewater
permit.
MERCURY MONITORING REQUIREMENTS
The proposed permit requires mercury to be measured in stormwater samples by EPA Method
1631E, which can detect levels as low as 0.5 ng/l. This requirement is consistent with recent
federal rule-making that requires NPDES permittees to monitor discharges with sufficiently
sensitive test procedures approved under 40 CFR §136. Modifications to 40 CFR §122.44(i) require
a method that has a minimum level (ML) at or below the effluent limit (not applicable here), or the
lowest minimum level (ML) of EPA approved analytical methods for the measured parameter.
Based on results, Method 1631E will be required to quantify levels in these discharges. NC DEMLR
understands that this method is more costly and requires a more intensive sampling protocol than
most other parameters, and that fish tissue sampling will be provided during the permit cycle.
Therefore, no benchmark applies that would trigger tiered response actions. Proposed permit
provisions also allow the permittee to use field blank and/or method blank concentrations to adjust
reported mercury levels as long as documented is submitted with the Data Monitoring Report
(DMR).
FLEXIBILITY IN TIER RESPONSES
Tier Two actions (upon two consecutive benchmark exceedances at an outfall) proposed in this
draft permit differs slightly from the Program’s standard template and includes step 6. That step
provides an opportunity for the permittee to propose an alternative monitoring plan for
approval by the Region:
5. Alternatively, in lieu of steps 2 and 3, the permittee may, after two consecutive exceedances,
exercise the option of contacting the DEMLR Regional Engineer as provided below in Tier
Three. The Regional Engineer may direct the response actions on the part of the permittee
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as provided in Tier Three, including reduced or additional sampling parameters or
frequency.
6. If pursuing the alternative above after two consecutive exceedances, the permittee may
propose an alternative monitoring plan for approval by the Regional Engineer.
The permit therefore allows the permittee to petition the Regional Office for monitoring changes
sooner than Tier Three (upon any four benchmark exceedances) and gives guidance on one option
to take. For example, the permitttee may request that mercury only be monitored semi-annually
under the tiers, or that only parameters over the benchmark be monitored more frequently. In this
way, changes to the monitoring scheme for any outfall could be handled outside of a permit
modification.
OTHER PROPOSED REQUIREMENTS
It is standard for Stormwater Pollution Prevention Plan (SPPP) requirements to include an
annual certification that stormwater outfalls have been evaluated for the presence of non-
stormwater discharges, and if any are identified, how those discharges are permitted or
otherwise authorized. The draft permit requires this facility to submit the first
certification to DEMLR no later than 90 days after the effective date of the permit
(Part II, Section A.).
Requirement to submit a request for permit modification if the facility identifies or creates
any new outfalls, removes outfalls, or alters any drainage area that changes potential
pollutants. This site may trigger this requirement during demolition or ash removal
activities.
Standard text that allows a permittee to forgo collecting samples outside of regular
operating hours was omitted in Part II because this power plant is not currently operating.
The Division expects the permittee to apply best professional judgment and consider the
safety of its personnel in fulfilling sampling obligations under the permit.
Proposed federal regulations will require electronic submittal of all discharge monitoring
reports (DMRs). 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. Permit provisions addressing this impending requirement is included in
Part III, Section B. (General Conditions), 3.e.
Quarterly Qualitative/Visual Monitoring to assure regular observation of outfalls
throughout year.
INSTREAM MONITORING
The facility historically had several monitoring stations located upstream and downstream.
Instream sampling has been for balanced and indigenous populations assessment (BIPA) in
Mountain Island Lake near Riverbend Steam Station and for wastewater permit in-stream
monitoring requirements. Upstream sampling for the wastewater permit is approximately 2-
miles upstream of the ash pond discharge (station 278.0), and downstream sampling (station
277.5) is approximately 0.5-miles downstream of that discharge. Monitored parameters between
years 2011-14 were As, Cd, Cr, Cu, Pb, Se, Zn (all by EPA Method 200.8), Hg (EPA Method 245.1),
and Total Dissolved Solids (TDS, SM2540C). All constituents were below water quality standards
for the six sampling events at each location. Refer to the document titled “Riverbend In-Stream
Monitoring Plan 2011-Present” for a summary of results. Division of Water Resources’ NPDES
wastewater permitting staff has recommend that Duke Energy continues up- and downstream
monitoring until wastewater discharges cease. That sampling is not necessarily performed during
rain events.
Additional instream sampling in April 2014 for a broader list of metals and other parameters also
did not show any results above water quality standards. Methods for metals analyses were the
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same as noted above. In-stream monitoring is not proposed in this draft NPDES stormwater
permit.
FISH TISSUE MONITORING
Wastewater permit NC0004961 required fish tissue monitoring for As, Se, and Hg near the ash
pond discharge once every five years. Sunfish and bass tissue were analyzed. The results were
below action levels for Se and Hg (NCDHHS) and screening value for As (NCDENR). The proposed
stormwater permit requires the permittee to submit a copy of future monitoring results to the
DEMLR Stormwater Permitting Program (Central Office) within 30 days of receiving results and
indicate the location of sampling in relation to stormwater discharge outfalls. DEMLR is requiring
the fish tissue analysis results be submitted separately because the proposed NC0004961 permit does
not require submittal to DWR until application for permit renewal.
PROPOSED SCHEDULE FOR PERMIT ISSUANCE:
Draft Permit to Public Notice: March 2015 (est.)
Permit Scheduled to Issue: June 2015 (est.)
STATE CONTACT:
If you have any questions about any of the above information or the attached permit, please contact
Bethany Georgoulias at (919) 807-6372 or bethany.georgoulias@ncdenr.gov.
Fact Sheet
NPDES Stormwater Permit NCS000549
Page 11
STORMWATER SAMPLING RESULTS FROM RIVERBEND (MAY 2014):
Fact Sheet
NPDES Stormwater Permit NCS000549
Page 12
STORMWATER SAMPLING RESULTS FROM RIVERBEND (JUNE-JULY 2014):
Fact Sheet
NPDES Stormwater Permit NCS000549
Page 13
STORMWATER SAMPLING RESULTS FROM RIVERBEND (JUNE 2008, FROM ORIGINAL APPLICATION SUBMITTAL):
Parameter Current
Benchmark
Outfall SW001
(mg/l)
Outfall SW002
(mg/l)
Outfall SW003 (mg/l)
(*composite)
Oil and Grease 30 (15, non-polar) ND ND, 27.6
ND
Aluminum 0.75 mg/l 0.915 1.58 0.753, 0.897*, 0.366
Arsenic 0.34 mg/l 0.0054 ND 0.005, ND*, ND
Barium N/A 0.0339 0.0517 0.115, 0.0222*, 0.0226
Boron N/A 0.0795 0.0915 0.072, ND*, ND
Cadmium 0.003 mg/l 0.0013 0.0012 ND
Chromium 0.9 (Cr III) mg/l,
0.016 (Cr VI) mg/l
ND ND ND
Cobalt N/A ND ND ND
Copper 0.010 mg/l 0.0684 0.0333 0.0533, 0.0182*, 0.0153
Iron N/A 2.0 5.79 21.2, 0.999*, 0.447
Magnesium 32 mg/l 1.7 3.52 9.57, 0.934*, 1.210
Manganese N/A 0.0754 0.117 1.38, 0.0792*, 0.0417
Nickel 0.335 mg/l 0.007 ND 0.0068, ND*, ND
Selenium 0.056 mg/l 0.062 0.0562 ND
Silver 0. 3 g/l ND ND ND
Titanium N/A 0.0256 0.0813 0.0299, 0.0403*, 0.0132
Zinc 0.126 mg/l 0.863 0.486 2.29, 0.758*, 0.748
Mercury 12 ng/l ND (<0.00020) ND (<0.00020) ND (<0.00020)
Apparent Color N/A ND ND, 180
ND, 40.0
TSS 100 mg/l 29.3 13.1, 67.7 151, 13.1
BOD 30 mg/l 13.0 5.2 72.9, 54.9*
Nitrogen,
Ammonia
30 mg/l 1.7 0.90, 0.90 0.80, 0.25*, 0.90
Nitrogen, Total
Kjeldahl 20 mg/l 2.4 7.7, 1.5*, 1.3
Nitrogen NO2 +
NO3 10 mg/l 1.5 1.0, 1.0 1.2, 0.78*, 1.0
Phosphorus 2 mg/l 0.53 0.12 1.6, 0.16*, 0.20
Phenol 4.5 mg/l (Trout) ND 0.45
Chloride 860 mg/l ND, 5.8 ND
COD 120 mg/l ND 49.0 233, 58.0*, 104
Sulfate 500 mg/l 17.3, 20.7 17.3, 10.3