NCS000580_Mayo DRAFT Permit Fact Sheet_20160831

DENR/DEMLR
FACT SHEET FOR NPDES STORMWATER PERMIT DEVELOPMENT
NPDES No. NCS000580
Facility Information
Applicant/Facility Name:
Duke Energy Progress, Inc./ Mayo Electric Generating Plant
Applicant Address:
410 South Wilmington Street, Raleigh, NC 27601
Facility Address:
10660 Boston Road, Roxboro, NC 27574
Permitted Flow:
N/A Stormwater Discharges Only)
Industrial Activities:
Primary SIC Code: 4911- Electric Services
Permit Status:
New NPDES Stormwater Permit
County:
Person County
Miscellaneous
Receiving Stream:
Mayo Creek
Regional Office:
Asheville
Stream Classification:
WS-V
State Grid / USGS Quad:
303 d Listed?
H , statewide
Permit Writer:
Mike Randall
Subbasin:
22-58-15- 0.5
Date:
August 23, 2016
Facility Location: Lat. 36° 31' 17" N Long. 78' 53' 39" W
BACKGROUND
The Mayo Electric Generating Plant (Mayo) is a dual boiler coal fired electric generating plant with a
net generating capacity of 745 megawatts.
Four areas of coal handling include the coal car unloading.area, transfer boom, conveyor belt
system and coal pile.
Coal Car Unloading Area
Coal cars are positioned over a below grade open transfer it. +The unloading area is equipped
with a dust suppression system that is used to minimize the generation of dust during coal car
unloading. Water spray nozzles are positioned such that as coal cars are unloaded into the
transfer pit, the spray suppresses dust. Various conditions such as wind, rain, and the condition
of coal dictate the need for dust suppression. Stormwater drainage from the area flows (via the
ash pond) to NPDES wastewater discharge point, 002.
Transfer Boom
The transfer boom is another area where there is a potential to create dust. In order to
minimize dust the boom is raised or lowered. Stormwater drainage from the area flows (via the
ash pond) to NPDES wastewater discharge point, 002.
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Conveyor Belt
The conveyor belt system is covered to reduce dust. Efforts are in place to ensure the conveyor
belts remain covered. Stormwater drainage from the area flows (via the ash pond) to NPDES
wastewater discharge point, 002.
Coal Pile
The coal pile is known as a "live pile." This is because of the way the coal is fed or reclaimed to
the unit or boilers. Coal is pulled from the bottom of the pile and therefore reduces dust.
Stormwater that comes into contact with the coal pile is routed to (via the ash pond) to NPDES
wastewater discharge point, 002. Stormwater drainage from the area flows (via the ash pond)
to NPDES wastewater discharge point, 002.
In the spring of 2009 the FGD system went into service. The FGD system requires individual
storage piles limestone and gypsum. These storage piles are located west of the powerhouse block
near railroad tracks. Stormwater from this area and Stormwater that comes in contact with the coal
pile is routed (via the ash pond) to NPDES wastewater discharge point, 002. Limestone and
gypsum are transported to and from the storage piles via haul trucks. Gypsum haul trucks are
required to be rinsed to remove residual prior to leaving the plan area. The truck rinse activity is
conducted inside a containment that processes the used water through an oil water separator that
is routed (via the ash pond) to NPDES wastewater discharge point, 002. During transportation, the
haul trucks are required to be covered.
In 2010, a hydrated lime injection system was added for flue gas conditioning. The system consists
of a silo, truck unloading and injection equipment. The truck unloading area includes secondary
containment. Hydrated lime is delivered by closed tankers.
In 2011, magnesium hydroxide and calcium carbonate systems were added to reduce coal
combustion boiler slag impact. The truck unloading area consist s of a secondary containment
system with a sump that allows released chemicals to be collected and pumped into the storage
tank. After evaluation rain water is released outside the containment via sheet runoff.
FACILITY STORMWATER DRAINAGE
Outfall 004 t)cl
Outfall 004 is located on the northeast side of the facility drid drains to the reservoir through catch
basins and the stormwater sewer conveyance system. The drainage area for outfall 004 is primarily
the loading dock and outside storage area. Materials stored in the area include empty lubricant
drums, structural steel, pipes and large equipment. There is- a concrete unloading area and the rest
is comprised of loose gravel. There is a small shed for hazardous waste, chemicals and oils. A
portion of the outside storage area is dedicated for construction project laydown area. The
concrete truck washout area is controlled to ensure no free flowing liquids leave the area or comes
into contact with stormwater runoff..-> �
Outfall 005 �
Outfall 005 is located on the ndrtTieast de of the facility and is the end point of the plant's primary
stormwater sewer system. Drainage area includes area around the boilers and turbine buildings,
precipitators, and the roofs of the machine shops, administration building, warehouse, parking lot,
and water supply treatment, ash storage silo, hydrated lime silo, and transformers. Also, is a
grassed area used as a marshalling area for construction activities and maintenance projects, and
for a future Unit 2. The area is primarily gravel and grass. Potential pollutants for outfall 005
include coal, coal ash, and sediment. Mobil equipment is also a potential source of pollutants.
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In 2004 SCR installation included anhydrous ammonia storage tanks and a truck unloading area.
Secondary containment is provided for the storage tanks and unloading area. Secondary
containment is routed to the ash pond to NPDES wastewater discharge point 002.
During the 2009 FGD Scrubber installation an additional transformer was added. The transformer
was installed with secondary containment routed to the existing oil water drainage and separation
system. The renovations also included the dry flyash collection system with load out and wheel
wash system.
In 2010, hydrated lime injection system was added for flue gas conditioning. The system includes a
silo, truck unloading equipment, and injection equipment. Secondary containment is provided for
the truck unloading area. Closed tanker trucks deliver hydrated lime.
Cooling tower Area - Outfall 006 a, b, c, d, and e.
Out fall 006 is located at the eastern end of the site and drains the area around the cooling towers,
including the roof of the chemical feed buildings and associated roads and parking areas. In the
cooling tower area there are five separate outfalls, Outfall 006 a, b, c, d, and e. Stormwater runoff is
collected in catch basins and conveyed to swales before collecting in a reservoir. The cooling tower
has a basin for recirculating cooling water and therefore does not directly contribute wo
stormwater runoff. Potential pollutants include sediment and mist from the cooling water tower.
Mobil equipment is also a potential source of pollutants.
Drainage are from Railroad Area - Outfall 007 a and b - removed in February 2001.
Main Plant Entrance Road - Outfall 010
The first 100 yards of the main plant entrance road, starting at the Boston Road and main plant
road intersection and traveling toward the plant, drains to the ash pond. The remaining drainage
are drains to Mayo Lake. The central drainage point for the road is located at a low point south of
the entrance to the picnic area entrance. The main plant entrance road was added to the
Stormwater Pollution Prevention Plan (SWPPP) due to limestone and gypsum truck traffic in the
spring of 2009. Potential pollutants could be coal ash, limestone, gypsum, petroleum, and hydrated
lime. Limestone delivery trucks are covered. Gypsum trpcks leaving with oduce ate washed and
rinsed before leaving the plant area.
41:
In 2009, Daily inspections of the plant entrance was establiie .
In 2010, the installation of the hydrated lime injection systentr flue gas conditioning resulted in
increased truck traffic. r'
In 2011, coal conditioning system 4LinVLIWrove coal combustion. The material is
delivered via closed tanker trucks.
BEST MANAGEMENT PRACTICESICMPSI
Specific containment and diverMkn mead[res include:
• Segregation of the work area
• Covering or enclosing the work area
• Diking the work area
• Diversion of stormwater runoff
• Dust Control
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Structural BMPs included:
• 2004 SCR installation including secondary containment for anhydrous ammonia storage
tanks and unloading area.
• 2009 FGD Scrubber, secondary containment for transformer and double walled mobile
equipment fuel tank, FGD drainage recycle system, covered dump trucks for flyash delivery,
truck wheel wash system with discharge to wastewater discharge point 002.
• 2010 closed tanker and secondary containment for hydrated lime.
• 2011 closed tanker and secondary containment for coal conditioning system (magnesium
hydroxide and calcium carbonate), secondary containment for truck unloading and product
tanks.
• Secondary containment for all above ground stationary oil storage tanks.
Periodic vacuuming of storm drain catch basins are conducted in high risk areas.
WHY THIS FACILITY IS SUBIECT 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 receivin areas; manufacturing
buildings; storage areas (including tank farms) for raw mate iaaIs, 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."
}
PROPOSED MONITORING FOR STORMWATER DISCHA�ES
&001
The Division considered potential polluta fro past and present industrial activities (coal-fired
electric generation, plant decommissioning, and future ash removal) and data submitted in the
application submitted October 13, 2014. Sampling for outfall 010 included 0&G, COD, TSS, Total
Nitrogen, Total Phosphorus, pH, Antimony, Arsenic, Barium, Beryllium, Boron, Cadmium, Chlorides,
Chromium, Cobalt, Copper, Fluoride, Iron, Lead, and Manganese, Mercury, Molybdenum, Nickel,
Selenium, Silver, Thallium, Vanadium, and Zinc, Aluminum, Color, Herbicides, Magnesium, Nitrate,
and TKN.
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
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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 site. All outfalls ultimately discharge to Mayo Reservoir.
Stormwater Discharge Outfall (SDO) Monitoring
Outfall 004, 005, Outfall 006 (a, b, c, d, and e) and Outfall 010
Total Suspended Solids (TSS)
Semi-annual monitoring (quarterly if coal or ash transport). BASIS:
Potential pollutant from drainage area and BMP effectiveness
indicator.
Priority Pollutant Metals Ag, As,
Quarterly monitoring only if coal or coal ash transported through
Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se,
this drainage area. BASIS: Coal combustion waste (CCW)
Tl, and Zn.
constituents; includes metals incorporated into the coal ash
monofill constructed for the company's Mayo Steam Electric Plant.
Boron
Quarterly monitoring only if coal or coal ash transported through
this drainage area. BASIS: Coal combustion waste (CCW)
constituent coal tracer.
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.
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 cpsponse to analytical
results above benchmark concentrations (Part II, Section B., following Tab 10). The tiered
structure of the permit provides the permittee and NCDEML wide flexibility to address issues that
may arise with one or more parameters and/or outfalls.
Metals benchmarks are calculated to mimic acute water qualitytandards 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 "1/z FAV" ). In most
cases, translation into total recoverable values is based on an assumed hardness of 25 mg/1 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 Perihitting Program applies this approach because of the ephemeral
nature of rainfall events. i
r
The Division may evaluate results W-Cfetermine 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
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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 , m L Total
0.09
Acute Aquatic Criterion, 1/2 FAV
Arsenic (As), m L Total
0.34
Acute Aquatic Criterion, 1/2 FAV
Beryllium (Be), m L Total
0.065
Acute Aquatic Criterion, 1/2 FAV
Cadmium Cd , m L Total
0.003
Acute Aquatic Criterion, 1/2 FAV
1/z FAV, based on (Cr III + Cr VI) acute thresholds
Chromium (Cr), mg/L (Total)
0.9
and assumption that industrial activities here are
not a source of hexavalent chromium.
Copper (Cu), m L Total
0.010
Acute Aquatic Criterion, Y2 FAV
Lead (Pb), m L Total
0.075
Acute Aquatic Criterion, Y2 FAV
Monitoring only, CCW/Coal Constituent. Hg
influenced by regional transport and wet
Mercury (Hg), ng/L (Total)
N/A
deposition. Values above 12 ng/L (NC WQ
standard) should be noted on the DMR but do not
trigger Tier Responses.
Nickel (Ni), m L Total
0.335
Acute Aquatic Criterion, 1/2 FAV
Polychlorinated biphenyl
Detected
NC Water Quality Standards vs. present Arochlors
compounds (PCBs), µg/L
quantitation levels (higher than standard)
1/2 FAV, NC -specific, based on 1986 Study on Se
Selenium (Se), mg/L (Total)
0.056
impacts in North Carolina
Acute Aquatic Criterion, 1/z FAV. (The Division
Silver (Ag), mg/L (Total)
0.0003
notes this value is below the practical quantitation
level (PQL) of 1 µg/L of EPA Method 200.8)
Monitoring only, CCW/Coal Constituent. Narrative
Boron (B), mg/L
N/A
National Recommended Water Quality Criterion.
Monitoring Only, CCW/Coal constituent. National
Thallium (TI), mg/L (Total)
N/A
Recommended Human Health Criterion.
Zinc Zn , m L Total
0.126
Acute Aquatic iterion, 1/2 FAV
Total Suspended Solids (TSS),
National Urban Run Af Program (NURP) Study,
mg/L
100
1983
Non -Polar Oil & Grease, EPA
Review of other state's daily maximum benchmark
Method 1664 (SGT-HEM),
15
concentration for this more targeted 0&G; NC WQ
mg/L
Standard that does not allow oil sheen in waters.
pH
6-9
j NC Water Quality Standard (Range)
WF
F
STORMWATER POLLUTION PREVENTIO
The proposed permit conditions ect 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
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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
0) 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 exddedafites'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 anflaalt rn ive monitoring plan for
approval by the Region:
Alternatively, in lieu of steps 2 and 3, the permittee may,- fter 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 as provided in Tier Three, including reduced or additional
sampling parameters or frequency.
If pursuing the alternative a ove aftertio consecutive exceedances, the permittee may
propose an alternative m W
lilan 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.
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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 Il, 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.
SECTION D ELECTRONIC REPORTING OF MONITORING REPORTS [G.S. 143-215.1(b)]
Federal regulations require electronic submittal of all discharge monitoring reports (DMRs) and
program reports and specify that, if a state does not establish a system to receive such submittals,
then permittees must submit monitoring data and reports electronically to the Environmental
Protection Agency (EPA). The final NPDES Electronic Reporting Rule was adopted and became
effective on December 21, 2015. 1&
PROPOSED SCHEDULE FOR PERMIT ISSUANCE:
Draft Permit to Public Notice: [Date]
Permit Scheduled to Issue: [Date]
STATE CONTACT: At Ar r--
If you have any questions about any of the above information or the attached permit, please contact
Mike Randall at [phone] orr [e-mail].
W
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