NCS000548_Tier I Notification DEMLR Response_20251024

Eplin, Jerry W
From: Eplin, Jerry W
Sent: Friday, October 24, 2025 9:58 AM
To: La Sala, Joseph Scott
Subject: RE: [External] NCS000548 Marshall Steam Tier 1 ISW Notification
The notification has been received. Let us know if you need our assistance.
Rega rd,
Jerry W. Eplin, PE
Regional Engineer
North Carolina Department of Environmental Quality
Division of Energy, Mineral, and Land Resources
610 E. Center Ave. Suite 301
Mooresville, NC 28115
Office: [phone]
jerry.eplina-deg.nc.gov
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From: La Sala,Joseph Scott<[e-mail]>
Sent: Friday, October 24, 2025 9:13 AM
To: Eplin,Jerry W<[e-mail]>
Subject: [External] NCS000548 Marshall Steam Tier 1 ISW Notification
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Mr. Eplin,
Please accept this electronic submittal as official two-week notification for Tier 1 status regarding the
industrial stormwater system serving Marshall Steam Station, per Part D, Condition D-6, Table 9 of
Permit No. NCS000548.
On September 29, 2025, quarterly stormwater samples were collected at Marshall Steam Station and
samples were analyzed in accordance with the facility's permit. Analytical results for this monitoring
event were received by Duke Energy on October 14, 2025. Upon review of the results, outfall SWO08 was
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noted with Total Suspended Solids (TSS) concentration exceeding the permit benchmark of 100
milligrams per liter(mg/L; or at 140 mg/L). This is the first benchmark exceedance at SWO08 since
November 2018 and qualifies this outfall into Tier I status.
A Tier 1 stormwater system inspection was completed at the outfall on October 15, 2025. Good
housekeeping measures that have been in place since 2018 include quarterly inspections and cleaning
of paved surfaces around the outfall inlet. However, it was determined from the tier inspection that
heavy traffic along paved areas upstream of the SWO08 during recent outage work was likely the result to
the elevated TSS measured at this outfall.
The December 2018 tier notification for to the agency for this outfall last reported that the facility had
plans to begin a substantial repaving effort in early 2019 that would result in redirecting stormwater in
many areas around the main power block to the facility's wastewater treatment system. As anticipated,
the paving efforts, completed in 2021, resulted in a reduction of vehicle tracking from unpaved areas
around the south and east of the main power block, and is likely attributable to the significant reduction
in TSS reported for SWO08 over subsequent years.
Similar plans to further pave along the eastern driveway of the plant are now underway and include
paving the area of SWO08 which will result in permanent abandonment of the outfall and redirecting of
stormwater flow. This work is to be completed by end of November 2025. As the NCS000548 permit
renewal application was recently submitted to the agency(submitted 9/30/25; received 10/1/25), the
abandonment and closure of outfall SWO08 may require that the permit be modified during the draft
review process. Closure of the outfall will be documented as the corrective action to the tier report
which will be retained in the facility SWPPP.
Please do not hesitate to contact me if you have any questions about this electronic notification report.
Thanks,
Scott
t7 Scott La Sally P�
Lead EHS Consultant I Marshall Steam Station
Office 828.478.7820 1 Mobile [phone]
8320 East NC HWY 150
Terrell, NC 28682
joseph.lasalaa_duke-energy.com
�DUKE
' ENERGY.
Society grows great when old men plant trees whose shade they know they shall never sit in.
Ancient Greek Proverb
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