NC0031879_NOV2023LV0274_Response_20230504

May 4, 2023
Mr. Daniel Boss, Assistant Regional Supervisor
Water Quality Regional Operations Section, NCDWR, NCDEQ
Asheville Regional Office
2090 U.S. Hwy 70
Swannanoa, NC 28778
Subject: Notice of Violation
Tracking #: NOV-2023-LV-0274
Permit NO. NC0031879
Corpening Creek WWTP
McDowell County
Dear Mr. Boss,
I am writing in response to your letter dated April 24, 2023, and received by the City of Marion
on April 28, 2023, the subject of which was a Notice of Violation and Intent to Assess Civil
Penalty for a violation of the monthly limit for Ammonia Nitrogen (NH3-N), which occurred
during the month of February 2023. The monthly limit for NH3-N is 3.3 mg/l. The value
reported for the monthly average for February was 4.75 mg/l. The exceedance of the monthly
average limit occurred due to the failure of two surface aerators in the aeration basin. The
aerators were repaired as quickly as possible after their failure, but because the dissolved oxygen
in the aeration basin was low for approximately 12 days, the nitrification rate was reduced and
the N113-N concentration increased. The nitrification rate improved as soon as the repaired
aerators were installed and by February 28 h, the NH3-N concentration was down to 0.8 mg/l.
Corrective actions taken for the failed aerators and increased NH3-N concentration included
making repairs to the inoperable aerators as quickly as possible. In addition, WWTP staff have
implemented a plan to keep up to two repaired aerators on hand and ready to be installed, should
an aerator or aerators fail. As soon as an aerator fails, the plan is to install a repaired aerator and
begin repairs on the failed aerator immediately. Factors that could affect staff s ability to always
have a repaired aerator on hand include the availability of parts and the number of aerators that
fail at one time.
The City respectfully requests that a civil penalty not be assessed for the violation. As described
above, two aerators failed at the same time and WWTP personnel repaired both aerators as
quickly as possible. In addition, they implemented a plan to try to keep the same problem from
occurring in the future by maintaining more redundancy in aerators. If you have any questions
or require additional information, please contact me at 828-652-4224 or WWTP Superintendent
Tim Horton at 828-652-8843. Thank you in advance for your time and consideration.
P.O. Drawer 700 • Marion, North Carolina 28752

Sincerely,
r
J. Brant Sikes
Public Works Director
cc: Bob Boyette, City Manager
Tim Horton, WWTP Superintendent
Lauren Armeni, Environmental Specialist II, ARO