Mayo Monofill General Permit File (26)

NCG120101
December 20, 2013
B. Georgouhas
Duke Energy Progress, Inc. — Mayo Steam Electric Plant Monofill for Coal
Combustion Residue (CCR)
Summary
Thi"sfacility submitted a Notice, of Intent (NOI) to be covered under General Permit NCG120000
(Landfills). The stormwater discharge drains to a Bowes Branch (Class C -Sw), in the Roanoke River
Basin. The stream segment is not listed as'impaired or subject to a Total Maximum Daily Load (TMDQ
This facility is located in Person County, handled by the Raleigh Regional Office.
History
The Mayo Steam Electric Station (separate from the Monofill site) Is permitted under the NPDES
wastewater permit no. NC0038377. In 2009, that permit included stormwater discharges; .however,
NPDES stormwater-requirements, have since been split -out and,will be; permitted separately. Aseparate
NPDESstormwater °permit for the Mayo Steam'Electric Plant has:never been developed because of
unresolved monitoring Issues for coal -fired power plants.
To address a diminishing capacity in Mayo's ash pond and risk,of violating effluent limits in that pond
discharge, the company concluded the wet ash handling system had to be eliminated. The plant began
converting to a dry bottom ash handling system (which was 98 percent complete with that by late
September 2013). In addition, a proprietary bioreactor system to remove Hg, Se, and As from the flue
gas desulphurization (FGD) waste stream (directed to the ash pond) was installed, and new, proposed
effluent limits were put into the discharge permit. However, the system has not performed as expected,
and the plant has not been able to meet effluent limits. In June 2012, a Special Order by Consent (SOC)
Was finalized to address violations of, limits in NCO038377 for ash pond outfa'll 002.
Of the remaining options to comply with the SOC, the company decided to evaporate -all the water-in a
zero liquid discharge (ZLD) system — basically by using a very large evaporator. The evaporator will
reduce water volumes to 5 -10 percent of the initial volume, and what remains will be used to condition
dry ash for transport to the monoflll under construction.
General Permit Application Review
a) The permit application has been signed and sufficiently completed. Yes.
b) The SIC code accurately describes thisfacillty's activities and qualifies for,coverage under
this general permit. Application noted SIC 4911 (Electric Power Generation), but this NOI
is forstormwater discharges from the�monofill'for coal combustion, residue (CCR) that will
be transferred from Mayo Steam Plant's new Zero Liquid Discharge (ZLD),System.
The NCG12 general permit is•applicable to stormwater discharges.associated with landfills
permitted by NC Division of Waste Management under NC G S. 130A -294, and therefore
under consideration for a Certificate of Coverage. Additional monitoring because of the
nature of the material is recommended as a condition of coverage (see special notes).

N CG 120101
December 20, 2013
B. Georgoulias
c) Other permits of interest:
#1 DWM Permit No.73054NDUS -201,2 (Permit to Construct — Phase 1) for Monofill
requires surface water monitoring per the approved Water Quality Monitoring Plan
(WQMP). DWM permit contacts are Larry Frost and Elizabeth Werner. See attached
excerpts from the WQMP and Solid Waste Industrial Landfill Permit.
Obligations require semi - annual monitoring of two upstream points and one downstream
point for numerous metals, BOD, COD, TDS, TOC, pH, conductivity, and temperature.
#2 NPDES Wastewater Permit(J*JJJW7) for Mayo Steam Plant (separate but nearby
location): the draft permit requires fish tissue sampling for mercury, arsenic, selenium and
thallium up- and downstream. A monitoring plan will be submitted by the company and
approved by NCDENR /DWR. The draft has not been finalized because of on -going litigation.
d) Regional Office input requested: 11/27/2013 (RRO contacts D. Parnell of DEMLR and A.
Romanski of DWR).
RO Approval received: 12/18/2013 (see attached e-mail and correspondence from A.
Romanski.) DEMLR concurrence on 12/20/2013 (conference call with D. Parnell and J.
Holley).
e) Will a Post - Construction Permit be required? No, outside of Roxboro in Person County. No
permit unless county has other requirements.
f) Review of data from haul road stormwater discharge data from Mayo Steam Station:
NCO038377 required semi - annual sampling and analysis for several parameters at
stormwater discharge outfall 010 since it became effective on November 1, 2009. However,
only three stormwater DMRs were located in Central Files. Samples were from 9/21/2013;
3/15/2012; and 8/27/2011.
Shannon Langley e- mailed copies of samples from 9/21/2013 (also in CF); 5/6/2013;
2/19/2013; 10/29/2012; 6/11/2012; 3/15/2012 (also in CF); 8/27/2011(also in CF);
5/17/2011; 11/4/2010; and 4/21/2010.
Sample concentrations exceeded benchmarks only once: 5/17/2011 for TSS (152 mg /1), Cu
(9.4 ug /1), and Al (4430 ug /1).
g) Special Notes:
This site will be a fully -lined landfill (approx. 34 acres) for coal combustion residue (CCR)
with potentially very high concentrations in metals. A 1- million gallon capacity leachate
collection system is being installed just west of the landfill and will direct wastewater to the
wastewater treatment system permitted under NC0038377.

NCG120101
December 20, 2013
B Georgoulias
Access roads would be handled under the Mayo Steam Station stormwater NPDES permit
[yet undeveloped ] Truck loads are to be covered, and truck wheels will be washed upon
leaving the plant. - 1.
h) Stormwater Permitting Recommendations:
The NCG12 permit already requires monitoring for Chemical Oxygen Demand (COD), Fecal
Coliform, and Total Suspended Solids (TSS). COD will also be sampled up- and downstream
per the Water Quality Monitoring Plan (WQMP) in the Solid Waste, Permit. Several metals
will also be sampled'in- stream as part.of the WQMP, though not necessarily during storm
events.
#1: Recommend sampling all outfalls for following parameters once in the,first sampling
period (between Jan 1 -Jun 30, 2013), and again in the,sampling period before renewal
application (between,Jul 1— Oct,31, 2017) of the permit, without any benchmarks:
Antimony (Sb) [prionty metal]
Lead (Pb)' [priority metal]
Arsenic (As)' [pnonty metal]
Mercury ,(Hg)' [pnornty metal]
Barium (B)'
Molybdenum (Mo)
Beryllium (Be) [prnontymetal]
Nickel (M)',[prionty metal]
Boron (B)'
Selenium (Se)' [prronty metal]
Cadmium (Cd)' [prronty metal]
Silver (Ag)' (pnonty metal]
Chloride'
Sulfate'
Chromium (Cr)' [pnonty metal]
Total Hardness (mg /1)
Copper (Cu)' [pnonty metal]
Thallium (TI)' [pnontymetal]
Fluoride'
Zinc (Zn)' [pnonty "metal]
'These parameters-will be monitored up- and downstream semi- annually as part of the
approved Solid Waste Permit WQ Monitoring Plan.
RATIONALE: The first sample will yield a baseline forstormwaterdischarges when the
° monofill operation ►s;still new, and the last sample will compare discharges after at least
three years of operation. The list includes -the 13 priority pollutant metals (40 CFR, §423,
App. A) and other constituents, (chloride, sufate, etc.), that may be present,in highly
concentrated amounts because of ZLD water used to condition the CCR transported to the
monofill. 'The amount of.dissolved metal is hardness - dependent in many cases and
determines toxicity potential. Results will also help determine whether it is appropriate to
continue coverage under the General Permit at renewal
This list is based on potential ,CCR constituents and recommendations by the Raleigh
Regional Office DWR (A. Romanski, 12/2/2013 e-mail attached). Aluminum (Al) and
manganese (Mn) were omitted because water quality standards do not apply to the
receiving waters (Class C) for the monofill, and they are not priority metals. However, Mn is
referenced in the SOC because effluent limits have posed a problem (NOTE: Mayo Reservoir
is classified as a Water Supply water, WS -V, with a corresponding Mn standard).

N CG 120101
December 20, 2013
B Georgouhas
These metals.and other compounds are also associated with air pollution, control technology
(APC) waste streams like flue gas desulphurization systems. Molybdenum (Mo) does not
have an NC WQ standard, but there is a stormwater benchmark for Mo based on acute
toxicity data. Along with As, Ba, B, Cd, Cr, Hg, Sb, Se, and TI,, the fate of Mo in APC residues
has been studied as part of on -going research by U.S. EPA's National Risk Management
Research Laboratory (Environ. Sci. Technol. 2010, 44, "Evaluating the Fate of Metals in Air
Pollution Control Residues from Coal -Fired Power Plants'_').
For reference, the following stormwater benchmarks are associated with these parameters:
Parameter
Benchmark °�a
a peter' _
Benchmar
Antimony (Sb)
0.09 mg /I
Lead (Pb)
0.075 mg /I
Arsenic (As)
0.34 ,,mg /I
Mercury (Hg)
12 ng /1
`Bariurn,(B)
N/A (WSstd only,, Nat'l
Human, Health Criterion)
Molybdenum,(Mo)
510 mg/.l (no WQ std or
Nat'l criterion, but
some states have a std)
Beryllium (Be)
0.065 mg /,I
Nickel (Ni)_ _
0.335 mg /I
Boron (B)
N/A (Narrative Nat'f WQ
criterion, 1986)
Selenium (Se)-
0.056 mg /I
Cadmium (Cd)
0 003 mg /I
Silver (Ag)
0.003 mg /I
Chloride
860 mg /I
Sulfate
500 mg /I
Chromium (Cr)
0.9 mg /I
Total Hard__ness,(mg /1)
N/A
Copper (Cu)
0.010 mg /I
Thallium (TI)
N/A (Nat'l Human
Health Criterion)
Fluoride
6 mg /I
Zinc (Zh)
0.126 mg /I
#2: Also recommend supplementing each semi - annual sampling event with analyses for
conductivity, pH, arsenic, selenium, and, boron.
RATIONALE: Conductivity is an, indicator parameter of inorganic contaminants, and regular
mdnitoring'through the permit cycle will establish values characteristic of the stormwater
from thi's site. The pH`is also an indicator parameter,and important for interpretingloxicity
of-total recoverable'metal concentrations. Both are also rapid and simple parameters to
measure'in the field, and offer an opportunity for prompt attention if,an issue'arises. Both
arsenic and selenium are constituents in CCR, and Sevaistewater limit, violations are
addressed by the SOC (per wastewater limit violations recorded in BIMS for DMRs submitted
in 2011 -12). There are NC Water Quality standards for both metals. Boron-is ,a tracer for
the presence of coal; regular monitoring will establish �a characteristic level in the discharge
and help the company identify excursions above normal ambient levels. Combining
measurement of these three elements with conductivity measurements may also establish
trend relationships for a more simple monitoring approach in the future.

• NCG120101
December 20, 2013
B Georgouhas
Stormwater concentrations over the following benchmarks should be noted on DMRs but
not trigger Tier Responses:
Based on a review of the haul road stormwaterAzita from the Mayo Steam plant, we do not
anticipate these benchmarks to pose a problem unless there is,a contamination issue in
need of attention. Data for these additional parameters should be submitted to Central
Office with the DMRs for this permit.
Phone and Meeting logs
9/11/2013: Meeting with T,oya Ogallo, Shannon Langley, and Steve Cahoon of'Duke energy Progress to
discuss project prior to, NOI submittal.
Questions
There were only three SDMRs in Central Files; has there been semi- annual stormwater sampling of SDO
010 at Mayo Steam Plant? Yes Shannon Langley e- mailed copies of the reports on 11/15/2013.
Where will fish tissue sampling for Mayo Steam Plant take place? Mayo Reservoir? Most likely.
Monitoring plan that requires fish tissue monitoring "near,the Ash Pond discharge "'.will besubmitted to
DWR for approval after wbstewater,permlt finalized, and locations will be defined in the plan Proposed'
NP,DES WW permit language suggests As, Se, TI, and Hg will be tested.