NC0003425_Request for Essential Maintenance_20160314

jr•. DUKEvia
-CCP
410 South Wilmington Street
ENERGYMail Code NC15
Raleigh, NC 27601
March 14, 2016
RECEIVED/NCDEQ/DWR
Mr. Jeffrey Poupart, Section Chief
NC Division of Water Resources MAR 1 6 21.'
1617 Mail Service Center Water Quality
Raleigh, NC 27699-1617 Permitting Section
Subject: Request for concurrence of
essential maintenance
Roxboro Steam Electric Plant
Permit Number: NC0003425
Person County
Dear Mr. Poupart,
In accordance with guidance received from you in a meeting on November 18th, 2015, Duke
Energy requests concurrence that temporarily lowering the west ash basin at the subject facility
to install an alternative spillway in the intermediate filter dike is considered "essential
maintenance" under the terms of the subject permit. The engineering plans for the alternate
spillway were submitted to the NC DEQ Dam Safety staff for approval on August 14, 2015.
While there is no immediate threat, the alternate spillway is necessary because an engineering
evaluation suggests the RCP riser structures for the intermediate filter dike do not meet the
criteria for structural stability under seismic conditions. When the alternate spillway is installed,
the existing RCP structure will be properly closed.
In order to install the alternate spillway, the ash basin water level must be temporarily lowered
by approximately two (2) feet. Duke proposes to lower the water level through the use of pumps
with floating intakes. The pumped water will be released through the existing flow path
upstream of internal outfall 002 and final outfall 003. Flows will be sampled and measured at
internal outfall 002 in accordance with the terms of the subject NPDES permit and results will be
reported on the monthly Discharge Monitoring Report. Verbal notification will be provided to the
DEQ DWR regional office at least 48 hours prior to commencement of lowering the water level
for installation of the alternate spillway.
Duke Energy requests written concurrence that this activity constitutes essential maintenance
and that Duke may proceeded upon DEQ Dam Safety's approval of the plans. If you have any
questions regarding this activity, please contact me at [phone] or
[e-mail].
Sincerely,
E. Shannon Langley
Lead Environmental Specialist

Cc. DEQ Regional Office Supervisor
Sergei Chernikov - DWR
Rob Miller—via email
Robert Howard —via email
Jake Muessen — via email
Mike Lazar— via email
Danny Satterwhite — ORC- via email
Shannon Langley— NCRH 15th floor