NC0025542_NOV-2022-LV-0231 Response_20220414

FECEIVED/NCDEOIDWR
North Carolina
Life. Well Crafted.
Public Utilities
April 14, 2022
W. Corey Basinger
Water Quality Regional Operations Supervisor
Mooresville Regional Office
610 East Center Ave., Suite 301
Mooresville, NC 28115
APR 2 5 2022
City of Hickory
WQROS PO Box 398
MOORESVILLE REGIONAL OFFICE Hickory, NC 28603
Phone: [phone]
Email: krhyneRhickorync.gov
RE: Notice of Violation & Intent to Assess Civil Penalty
Tracking Number: NOV-2022-LV-0231
Hickory -Catawba WWTP (NPDES Permit No. NC0025542)
Dear Mr. Basinger:
The purpose of this correspondence is to provide additional information to the referenced notice of violation (NOV-2022-
LV-0231) for your consideration in evaluating and assessing possible enforcement actions against the City of Hickory.
After discussion with the plant ORC, and assessing process controls, the following was determined:
The Catawba WWTP experienced heavy rain, very cold temperatures and a VFD drive failure on the mechanical aerator
during the month of February. The cold weather, current plant flow and the size of the oxidation ditch create a very low
Food to Mass Ratio and very long Mean Cell Residence Time which makes maintaining the biomass needed for
nitrification very challenging. A slight temperature, flow, or influent loading variation can cause a disruption in the
nitrification process. When this occurs, it makes it extremely difficult to meet the Nitrogen, Ammonia Total (as N) —
Concentration (C0610).
Remedial actions to correct this problem have been on -going. A supplemental carbon food source is being added to help
with the low F/M conditions and soda ash is being added to increase the alkalinity. The aerators are being cycled to aid
denitrification. Unfortunately, weather conditions are beyond our control and cold weather and heavy rainfall can inhibit
the nitrification process. During the winter months, the temperature in the plant will drop below 13 degrees Celsius, which
can inhibit the nitrification process and cause the effluent violations.
We believe the City of Hickory acts proactively to achieve compliance. Historically, NH3 has only been a challenge during
the winter months. As permitted, the plant can discharge up to 25 lbs. per day of NH3 at 1.5 MGD. At current flow of
0.080 MGD, the plant is discharging only 1.3 lbs. per day. We ask that this be considered as we feel that this NH3
discharge will not impair or disrupt the receiving stream.
The City of Hickory takes all violations seriously and works diligently in promoting and protecting the environment, health
and natural resources. The City hopes you will consider the above factors when evaluating possible enforcement actions.
Should you have additional questions or desire additional information, please do not hesitate contacting me at (828)322-
5075.
Sincerely
/Keith D. Rhyne
WWTP Superintendent
oi/C
PC: M. Shawn Pennell, Public Utilities Director
Andrew Foy, Utilities Environmental Manager
Josh Archambault, Hickory Catawba WWTP