NC0025453_NOD-2024-LV-0148_Response-to-Notice_20240925 (2)

September 25, 2024

Vanessa E. Manuel
Assistant Regional Supervisor
Water Quality Regional Operations Section
Raleigh Regional Office
Division of Water Resources, NCDEQ

Re: Notice of Deficiency, Tracking Number: NOD-2024-LV-0148, Permit # NC0025453, Sam’s Branch WRF, Johnston County
Ms. Manuel,
The Town of Clayton offers the following information regarding the NOD for the Low Dissolved Oxygen value of 5.7mg/L during the week of July 5th, 2024. The NOD was dated September 16th,
2024, and was received by the Town on September 19, 2024. On Friday July 5th, the Operator in the lab at the time calibrated the HACH HQ40d meter in the morning as usual for Dissolved
Oxygen regarding daily effluent compliance. When collecting the effluent grab sample, the Operator recorded a Dissolved Oxygen result of 5.68mg/L and failed to report it to Senior
Water Reclamation Staff as well as failed to collect another effluent grab sample for retesting. The Low Dissolved Oxygen value was discovered by the Lab Supervisor at the plant on
July 25th and Michael Hall from DEQ was notified due to Non-Compliance for that month. Manuel Vanessa and Tonja Springer from DEQ were contacted via email regarding this incident. When
looking through the calibrations of the DO meter for that day, it was discovered that at 22.1 degrees Celsius, the meter did not calibrate to the appropriate Dissolved Oxygen. According
to the Luminescence DO (LDO) Calibration Sheet, at 22.1 degrees Celsius with an Atmospheric Pressure of 753 mmHg, the meter should’ve calibrated to a DO approximately between 8.66mg/L
and 8.74mg/L. It was found that for that day, the DO meter only calibrated to 8.04mg/L; resulting in a lower effluent result that was non-compliant. The Town believes if the DO meter
had calibrated to the appropriate DO the effluent result would’ve been much higher and in compliance. The Town would also like to point out that the plant had recorded effluent DO results
of 7.58mg/L, 7.29mg/L, and 7.85mg/L respectively that same week prior to the day of the incident. For the DO in the effluent to drop off that significantly we believe is sufficient
proof that there was an issue with the calibration of the meter for that day. After discussions with the Lab Supervisor and the Laboratory Branch of DEQ it was deemed that the cap on
the probe of the DO meter had become dirty and that is why the initial calibration was thrown off. This cap has since then been replaced. The Town has also since implemented training
of staff with daily checks and protocols of the DO meter calibration to ensure the recorded effluent DO result would be accurate and compliant with our NPDES permit. If you have any
questions please feel free to contact me at [e-mail] or at (919)-594-0417.
Sincerely,  

David White  
Water Reclamation Superintendent  
Town of Clayton, NC
PO Box 879
919-594-0417
[e-mail]