NC0046728_Response to Notice_20240628

Town of Mooresville
North Carolina
Public Utilities
June 28,2024
Andrew H. Pitner, P.G., Regional Supervisor
Water Quality Regional Operations Section
Mooresville Regional Office
610 East Center Street Avenue
Mooresville NC 28115
Subject: Response to Notice of Violation
Tracking #: NOV-2024-LV-0521
Permit #: NCO046728
System: Rocky River Wastewater Treatment Plant
Dear Mr. Pitner,
This letter is in response to the Notice of Violation issued to the Town of Mooresville on June 18th,
2024. On April 30th, 2024, the Town of Mooresville exceeded their Monthly average permit limit
for BOD 5.Omg/L with a Monthly average result of 6.19mg/L."The Town of Mooresville would
like to ask that the following considerations be taken regarding the BOD violation that occurred
on April 30thh, 2024.
During the month of April (coincidentally the start of our summer limits), we experienced
some unexpected mechanical issues with our dryer which affected our efficiency and caused
higher than normal solids inventory. After assessing the scope of the repair and its effects on
the plant efficiency staff put together a plan to run the dryer at a slower rate while making the
repair. Unfortunately during this time we also experienced high rain events that caused higher
than normal solids entering the plant.
The higher than normal solids inventory caused us to lose treatment efficiency at the end of
the month resulting in a BOD result of 32mg/L on 4/30/23. Operations staff made immediate
adjustments to the plant including increasing the RAS and decreasing the speed of our aerators,
eventually turning some of the aerators off to hold some solids in the basins. These adjustments
are reflective of the BOD result of 6.9mg/L the following day. That one day high number
paired with our summer limits now into effect, ultimately caused us to be over our monthly
average limit for BOD.
As a precaution, the dryer was completely shut down during the month of May, and the wet
cake was transferred to a local landfill to reduce solids inventory at a faster rate.
The Town of Mooresville stives to maintain compliance with our NPDES permit and permit limits.
We consider any violation a serious matter and will continue to make any necessary operational
adjustments and/or system improvements to eliminate future violations form occurring. Thank you
P.O. Box 878 1 Mooresville, NC 28115 1 704-663-7282 1 mooresvillenc.gov

Town of Mooresville
North Carolina
Public Utilities
for taking our response in consideration. If you have any questions or concerns, please contact me
at 704-662-8341.
cere
SinJae,
isvater s stew
Superintendent
CC: Allison Kraft, PE, Town of Mooresville
P.O. Box 878 1 Mooresville, NC 28115 1704-663-7282 1 mooresvillenc.gov