NC0055786_Response to Notice_20231025

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LEXINGTON
NORTH CAROLINA
WATER RESOURCES
QUALITY FIRST
October 25th, 2023
Response to Notice of Violation with Intent to Assess Civil Penalty
Tracking Number: NOV-2023-LV-0780
Permit # NCO055786
Lexington Regional WWTP
To: Jennifer Graznak
Dear Jennifer,
The City of Lexington humbly requests consideration of this letter as further action is
considered. In the Month of August 2023, both BOD and Nh3N monthly and weekly limits were
exceeded.
The root problem took several weeks to determine and correct. Staff worked diligently to
determine the problem but with the Ammonia and BOD levels being so inconsistent it was
difficult to pinpoint where in the process the problem was. By late August the Aeration Train A
was finally determined to be where the high levels of BOD and Nh3N were originating from.
Staff immediately coordinated with Terra Nova Inc to come and pump out and wash the basin
once we got it drained. At the same time we also ordered 600 replacement aeration diffusers.
On Friday, September 1st 2023 staff began draining the basin to prepare for Terra Nova. Once
the basin was drained the magnitude of the problem was obvious. Staff found that several of the
original diffusers had broken off, fouled with grit and debris, and the air header pipes were
packed full of solids. It took Terra Nova 5 days to finish the wash out. With the help of the
Public Works Department, staff removed all of the old diffusers, rodded and jetted out the air
header pipes and replaced with new diffusers.
It should be noted that within hours of taking Train A offline and draining it, Nh3N levels
immediately returned to normal levels. The repairs to the Aeration System were finally
completed late August and since September the Plant is maintaining compliance and running
very well.
As you consider the need to assess Civil Penalties and the amounts, the City of Lexington
humbly requests consideration of the following facts and costs that we have incurred to correct
the situation in emergency fashion.
• Lexington requested Technical Assistance and Gary Hudson and Jesse Barnes visited on
August 4th. This was productive and Gary made some helpful insights.
• Because the lab results for Nh3N and BOD were fluctuating from day to day, it was
extremely difficult to pinpoint the problem.
• Once Train A was determined to be the problem, the basin was immediately drained.
• Lexington entered into an Emergency contract with Terra Nova for $63,950 to
Water Resources - Public Works - Engineering
28 West Center Street- Lexington, NC 27292 - 336.248-3930
WWW.LEXINGTONNC.GOV

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LEXINGTON
NORTH CAROLINA
WATER RESOURCES
QUALITY F I RST
immediately mobilize. A copy of the PO for this work is attached for reference.
• Lexington spent $20,927 to replace all 600 air diffusers in the basin. Receipt for the
diffusers attached for reference.
• Lexington staff worked around the clock to get the problem corrected.
As a result of the problems discovered in Aeration Train A, staff is currently ordering parts and
lining up equipment to address Aeration Train B as soon as possible. This will be costs of nearly
$85,000 that is not budgeted this year and will require a budget transfer. Lexington takes permit
compliance seriously and we are taking this action to avoid another exceedance event.
Sincerely,
Tom Ainson, Water Resources Director
Water Resources - Public Works - Engineering
28 West Center Street- Lexington, NC 27292 - 336.248-3930
WWW.LEXINGTONNC.GOV