NC0024406_Special Order By Consent_20180524

1111, DUKEDuke Energy
410 S.Wilmington Street
ENERGY® Raleigh,NC 27601
May 24, 2018
RECEIVED/DENRIDWR
Bob Sled e MAY 3 0 2018
g
NC Division of Water Resources Water Resources
1617 Mail Service Center Permitting Section
Raleigh,NC 27699-1617
Subject: Submittal of engineering report
SOC application
Belews Creek Steam station
NC0024406
Dear Mr. Sledge,
Attached please find the third party engineering reports referenced in Duke Energy's application
for Special Order by Consent for the subject facility dated May 22, 2018.
If there are any questions about this matter please feel free to contact me at(919) 546-2439 or
shannon.langley a,duke-enerey.com.
Sincerely,
E. Shannon Langley
Principal Environmental Specialist
Enclosures
Cc: Jim Wells - via email
Richard Baker—via email
Matt Hanchey—via email
Joyce Dishmon/Filenet—via email
Toya Ogallo—via email
www.duke-energy.com

ERM NC,Inc.
15720 Brixham Hill Ave.
Suite 120
May 24,2018 Charlotte, NC 28277
[phone]
www.erm.com
.■
10111111
Richard E. Baker Jr. }-!i•
Duke Energy :::`
526 S.Church Street ERM
Charlotte,NC 28202
Subject: Evaluation of Duke Energy Belews Creek Coal
Ash Basin
Dear Mr.Baker:
ERM NC, Inc. (ERM) has prepared this letter report to summarize the evaluation of the Duke
Energy Belews Creek Ash Basin operations and capability to meet National Pollutant Discharge
Elimination System (NPDES) effluent limits at Outfall 003. Based on ERM's review of the
treatment units and operations,ERM has concluded that the system cannot meet projected 2018
NPDES limits even at maximum efficiency of operation. The details of the evaluation are
presented in this letter report.
Background
The Belews Creek Steam Station (BCSS) is a coal-fired steam electric generating facility, with
wastewater discharges governed by NPDES Permit NC0024406. Operations at BCSS are
undergoing modifications to comply with the revised Effluent Limit Guidelines for the Steam
Electric Generating categorical dischargers, Federal Coal Combustion Residual (CCR) rules, as
well as the North Carolina Coal Ash Management Act.
The NPDES permit renewal application (August 2016), Duke Energy Carolinas, LLC (Duke)
outlines the planned changes to coal ash handling operations as shown by the Attachment 2 flow
diagram figures (in permit application) representing current and future water flows. In
particular, a new retention basin will be constructed, while the flow to the current active Ash
Basin will be ceased, and the only flow discharging from the Ash Basin will be from the closure
activities. These activities will include decanting of the surface water and dewatering of the ash.
Seepage from the basin will reduce in proportion to the basin water level,and ultimately cease as
the basin is closed.
Evaluation
The evaluation of the Ash Basin considers four topics,each of which is addressed as follows:
• An evaluation of existing treatment units,operational procedures and recommendations as to how
the efficiencies of these facilities can be maximized. The person in charge of such evaluation must
sign this document.

Evaluation of Belews Creek Coal Ash Basin
5/24/2018
p.2
The Ash Basin is a surface impoundment with a surface area of approximately 350 acres, and a
discharge flow of approximately 9 MGD. The principal use for this treatment unit has been the
storage of coal combustion residuals from the electrical generating plant. The treatment unit is a
gravity settling basin, which operates by allowing for sufficient hydraulic residence time for
suspended solids to settle in the basin, whereas the clarified effluent is discharged via an outlet
tower outfitted with stop log weirs to control the decant water level. The surface loading rate for
the basin is less than 0.001 GPM/ft2,which is a conservative hydraulic loading rate for gravity
settling.
The operation and maintenance of the Ash Basin is described in the BCSS O&M Manual (CCP-
PRG-BLC-OM-001, Rev 003). Operational activities pertinent to this evaluation include weekly
and annual inspections of the basin, monthly reading and review of instrument data, annual
CCTV video inspection of decant pipes and risers, and annual seepage collection video
inspection.
The operational performance of the Ash Basin, and specifically the solids settling, is directly
related to the flow into and out of the basin, and secondarily the water level maintained by the
outlet tower. Day to day fluctuations in flow due to the electrical generating plant operations
and rain events will have minor impact on the variation in water level due to the large surface
area. The stop logs are the primary means of setting and maintaining water level. The weekly
inspection activities will provide visual indication of problems with the outlet structure, for
example, if the water level is significantly below the weir,indicating significant leakage or mis-
aligned stop logs. The total suspended solids (TSS) recorded at Outfall 003 are typically less
than 5 mg/1,as further indication of the efficient performance of the settling operations.
• A certification that these facilities could not be operated in a manner that would achieve compliance
with final permit limits. The person making such determination must sign this certification.
The 2012 NPDES Permit NC0024406 effluent limitations for Outfall 003 are consistent with the
Steam Electric Power Generating Point Source Category Best Practicable Control Technology
(BPT)for ash transport water [40 CFR 423.12(b)(4)]. The projected 2018 NPDES Permit expands
the number of parameters with effluent limitations and differentiates between decanting
operations and the ash pond closure dewatering operations. The effluent parameter limit
comparison between permits is shown in Table 1,below:

Evaluation of Belews Creek Coal Ash Basin
5/24/2018
I).3
Table 1-NPDES Permit NC0024406 Effluent Limits-Outfall 003
Projected 2018 Limits
2012 Current
Limits Decanting Dewatering
Mon. Daily
Parameter Units Avg Max Mon.Avg Daily Max Mon. Avg Daily Max
Oil and
Grease mg/1 15 20 15.0 20.0 15.0 20.0
Total
Suspend
Solids mg/1 30 50 30.0 50.0 30.0 50.0
Total Iron mg/1 1.0 1.0 1.0 1.0 1.0
Total Copper mg/1 1.0 0.00788 0.01047 0.00788 0.01047
Sulfates mg/1 1502.4 1502.4 250.0 250.0 250.0 250.0
Chronic
Toxicity P/F @ 19% P/F @ 90% P/F @ 90%
pH s.u. 6-9 6-9 6-9
Chlorides RILQ 250.0 250.0
Total
Aluminum mg/1 111 6.5 6.5
Total
Cadmium mg/1 0.00324
Total
Selenium mg/1 0.0560 0.0050 0.0560
Total Lead mg/1 0. 0.07548 111694 0.07548
Total
Thallium mg/1 0 0.0020 0.0020 0.0020
Turbidity NTU 50 50
Ammonia mg/1 1.0 5.0 1.0 5.0
Total Arsenic mg/1 0.010 0.
Total
Molybdenum mg/1 0.160 011
Fluoride mg/1 1.8 Tri
Chromium
Ill mg/1 0.1177
Chromium
IV mg/1
Total Zinc mg/1
Total Nickel mg/1
Total Barium mg/1
Total
Antimony mg/1 111111
Note:Yellow=reduced limits;Red=additional parameters with limits
The projected 2018 NPDES permit reduces effluent limitations for total copper and sulfate,
increases the chronic toxicity percentage, and adds effluent limitations for (17) additional
parameters. Of these additional parameters,the majority(13)are for metals.

Evaluation of Belews Creek Coal Ash Basin
5/24/2018
p.4
As previously discussed, the Ash Basin was designed for and operates simply to remove
suspended solids by gravity settling. Surface impoundments, such as the Ash Basin, are
ineffective at removing dissolved solids,including metals in dissolved form. As noted in EPA's
Technical Development Document for the Effluent Limitations Guidelines and Standards for the
Steam Electric Power Generating Point Source Category(EPA-821-R-15-007,p.157):
"Surface impoundments can reduce the amount of TSS in the wastewater discharge provided
there is sufficient residence time. In addition to TSS, surface impoundments can also reduce
specific pollutants in the particulate form to varying degrees in the wastewater discharge.
However, surface impoundments are not designed to reduce the amount of dissolved
metals in the wastewater."[emphasis added]
The gravity settling operation of the Ash Basin has no ability to actively remove the dissolved
fractions of copper and the additional metals listed in the draft NPDES permit,and similarly for
chlorides and ammonia.
• The effluent limits that the facility could be expected to meet if operated at their maximum efficiency
during the term of the requested SOC(be sure to consider interim construction phases).
Duke Energy expects to be able to meet the following limits during the term of the requested
Special Order by Consent (SOC) for Belews Creek Steam Station. Upstream and downstream
monitoring of the Dan River and monitoring of Belews Lake upstream and downstream of the
power plant are expected to meet the 15A NCAC 02B Water Quality Standards for Surface Waters
(2B Standards). Instream monitoring of the Unnamed Tributary (UT) evaluating the potential
impacts from S-10 and S-11 seeps are expected to meet the limits shown in the table below:
pH 5-10
Cadmium 2 ug/1
Chlorides 700 mg/1
Mercury 0.1 ug/1
Hardness 800 mg/1
TDS 1500 mg/1
Duke Energy expects the discharge from Outfall 003 could meet the "phased interim"limits that
were in the April 16, 2018 draft NPDES permit A.(3) EFFLUENT LIMITATIONS AND
MONITORING REQUIREMENTS (Outfall 003 - normal operations/decanting) and A.(4).
EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS (Outfall 003 -
dewatering) The numeric limits proposed in the April 16,2018 draft were developed based on
the dilution of the Dan River as the receiving water (current 003 outfall location in 2012 NPDES
permit)compared to the 2018 location of Outfall 003 at the UT to the Dan River and zero dilution.
The April 16,2018 draft allowed a 4.5 year compliance schedule to meet the more restrictive limits
that are the same as the April 30,2018 NPDES permit draft.
Considering the decanting and future dewatering activities, these interim actions levels should
be achievable.

Evaluation of Belews Creek Coal Ash Basin
5/24/2018
p.5
• Any other actions taken to correct problems prior to requesting the SOC.
The station has attempted to operate the ash basin as efficiently as possible, and has completed
construction of the dry flyash system,which diverts a substantial portion of the material from the
Ash Basin,and reduces pollutant loading.
Conclusion
Based on my review of the available design and operating data for the BCSS Ash Basin,I have
determined that this treatment unit cannot be operated in a manner that would achieve
compliance with the final NPDES permit limits.
?/71_,2 ,1</).
Peter A. Flaherty,PE (NC#032922)