NC0006033_Correspondence_20220831

Strickland, Bev
From: Barker, Doug <[e-mail]>
Sent: Tuesday, August 30, 2022 10:42 AM
To: Tuvia, Ori A
Cc: Martinez, Rene; Shellenbarger, David; Scheringer, Stephanie B
Subject: [External] Eagle Road Power Issue Causing Sodium Hypochlorite Feed Disruption
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Ori,
This email is to follow up from our conversation the morning of 8/26/2022 concerning the power issue that caused an
interruption of the sodium hypochlorite feed at Eagle Road WWTP (NPDES NC0006033).
On Friday 8/26/22 at approximately 7:00 a.m. plant staff arrived on site to discover there was no power to the facility.
The Operator immediately went to check the emergency generators and found that both the main incoming power and
emergency generator breakers were in the open position. The Operator started the emergency generators by hand but
could not get the breakers to close. After further investigation, it was discovered that there was a ground fault trip on
the main incoming breaker which would not allow the emergency generator breaker to close.
At 7:25 a.m. staff was able to reset the ground fault trip and get the power restored to the plant. I arrived on site at 7:25
a.m. and started checking the plant processes and discovered that no sodium hypochlorite was discharging into the
chlorine contact chamber. I went to the chemical feed room and found the sodium hypochlorite feed pump off. I
started the pump in hand and reestablished chemical feed to the contact chamber. A DPD test of the chlorine contact
basin at approximately 7:50 a.m. indicated chlorine was present.
In an effort to determine the impact of this incident and per your request, fecal coliform sampling was promptly
performed at one upstream and two downstream locations from Eagle Road WWTP's discharge.
• The upstream sample was taken at Eagle Road WWTP's regular upstream monitoring location from the
Cramerton Bridge on North Main Street. The sample was collected at 11:42 a.m. and the test result was 132
cfu/100m1.
• The first downstream sample was taken at Eagle Road WWTP's regular downstream monitoring location from
the bridge at Armstrong Ford Road. The sample was collected at 12:07 p.m. and the test result was 210
cfu/100m1.
• A second downstream sample was taken further downstream at the Armstrong Road Bridge. The sample was
collected at 12:33 p.m. and the test result was 9 cfu/100m1.
On the morning of 8/26/22, both the generator maintenance and SCADA integrator vendors were called for emergency
site visits to check the generators and SCADA systems to ensure proper operation. Both emergency generators were
confirmed to be operating properly. It was discovered that the CPU for the main SCADA PLC was corrupted and had to
be replaced and reprogrammed.
Based on an examination of the Effluent Flow Chart recorder, the power loss occurred at 2:00 a.m. and was restored at
7:25 a.m. Therefore, it is estimated the sodium hypochlorite feed was not operating properly from approximately 2:00
a.m. until 7:50 a.m. From an evaluation of typical flow data for this period of time approximately 100,000 gallons were
discharged without full disinfection.
Please advise if additional information is needed.
Thanks,
Douglas Barker
Two Rivers Utilities
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Wastewater Resources
Treatment Plant Supervisor
704-214-9146
704-825-6593
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