NCS000548_Tier I Notification_20250409

Eplin, Jerry W
From: La Sala, Joseph Scott <[e-mail]>
Sent: Wednesday, April 9, 2025 10:32 AM
To: Eplin, Jerry W
Cc: Safrit, Don
Subject: [External] Marshall Steam Station - Notice of ISW Tier Status - Permit NCS000548
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Dear Mr. Eplin,
Please accept this electronic submittal as the written two-week notification as required by Part D,
Condition D-5, Table 8, regarding the industrial stormwater system serving the Marshall Steam Station.
On March 16, 2025, stormwater samples were collected at the referenced facility and analyzed in
accordance with NCS000548. Analytical results for this monitoring event were received by Duke Energy
on April 1, 2025. It was observed in the corresponding report that the benchmark for low level Mercury
was exceeded at stormwater outfalls SWO02 and SWO03 for the March 16' monitoring event. The
benchmark for Mercury is 12 nanograms per liter(ng/L) and the result for both outfalls SWO02 and
SWO03 is reported at 14 ng/L. This exceedance marks the first to be reported since February 2024 for
SWO02 and March 2024 for SWO03 and qualifies these outfalls into Tier I status. Pursuant to Part D,
Condition D-5 of the referenced permit, Duke Energy will document these exceedances and our
response/actions within our SWPPP and continue quarterly monitoring of the outfalls.
A subsequent stormwater system inspection has been completed at the outfall on April 8, 2025, and
associated BMPs in place appear to be maintained and in good working order. A plan to exchange the
activated carbon metal filter dikes located upgradient of SWO03 is underway. Scheduled quarterly
inspections and cleaning of the stormwater system is also being maintained at the site and outfall.
Please do not hesitate to contact me if you have any questions regarding this notification submittal.
Thanks,
Scott
scatt La &AA 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.
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