NC0031879_NOVNOI2021LV0408_RESP_20210608

CITY OF MARION
OFFICE OF
P. O. Drawer 700 THE PUBLIC WORKS DIRECTOR
Marion, North Carolina 28752
June 7, 2021
Mr. Daniel Boss, Assistant Regional Supervisor
Water Quality Regional Operations Section, NCDEQ
Asheville Regional Office
2090 U.S. Hwy 70
Swannanoa, NC 28778
Subject: Notice of Violation
Tracking #: NOV-2021-LV-0408
Permit NO. NCO031879
Corpening Creek WWTP
McDowell County
Dear Mr. Boss,
I am writing in response to your letter dated May 27, 2021 and received by the City of Marion on
June 3, 2021, requesting, within 10 business days of the receipt of the letter, an explanation of a
violation that occurred at the Corpening Creek WWTP during the month of April, 2021. The
violation, exceeding the weekly average limit for effluent TSS during the week of March 28"
(which ended on April 3`°), was caused by high flow passing through the plant while only one
secondary clarifier was in use. The WWTP recorded 5.1 inches of rainfall from 3/25/21 —
4/1/21, with the vast majority of the rain falling on 3/26/21 (3.3") and 4/i/21 (1.211). The total
effluent flow for 3/26/21 was 3.14 MG. With only one secondary clarifier in use, the plant was
hydraulically overloaded, which caused an effluent TSS concentration of 269 mg/l on March
30"'. The TSS concentration was down to 9.1 mg/1 on the following day, March 3 is', but the
high concentration from March 30a` was enough to cause the weekly average TSS concentration
to exceed the weekly limit of 45 mg/l.
As for corrective actions, WWTP personnel operated the plant in accordance with the standard
operating procedure for high flow to the best of their ability, considering only one secondary
clarifier was in service. As soon as the flow became low enough, personnel cleaned out the
contact chambers. All solids from the contact chambers were returned to the influent wet well
during the cleaning procedure. Those were the only measures staff could take to limit the
amount of solids washing out and to lower the TSS concentration in the effluent expeditiously.
As you are aware, only one secondary clarifier is being used because the other secondary
clarifier (secondary clarifier #1) is out of service awaiting a drive unit replacement. A new drive
unit was ordered in mid -March, 2021, but will not be shipped until approximately mid -July. The

City has contracted with Kemp Construction to install the new drive unit as soon as possible after
it is received.
The City respectfully requests that a civil penalty not be assessed for the violation because
personnel did everything possible to retain solids in the plant during the hydraulic overload, but
could not retain them due to Secondary Clarifier #1 being out of service. The City is working
expeditiously to return Secondary Clarifier #1 to service, but the new drive had to be built and
cannot be installed until it is received. If you have any questions or require additional
information, please contact me at 828-652-4224 or W WTP Superintendent Tim Horton at 828-
652-8843. Thank you in advance for your time and consideration.
Sincerely,
J. Brant Sikes
Public Works Director
cc: Bob Boyette, City Manager
Tim Horton, WWTP Superintendent