NC0006033_Correspondence_20211221

Strickland, Bev
From: Barker, Doug <[e-mail]>
Sent: Tuesday, December 21, 2021 1:27 PM
To: Tuvia, Ori A
Cc: Scheringer, Stephanie B; Shellenbarger, David
Subject: [External] Eagle Road Sodium Hypochlorite Feed Disruption
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Ori,
This email is to follow up from our conversation the morning of 12/20/2021 concerning the interruption of the sodium
hypochlorite feed at Eagle Road WWTP (NPDES NC0006033).
The Eagle Road WWTP is not required to be staffed 24/7. On each weekend day, Two Rivers Utilities has a wastewater
operator visit the facility and verify proper operation. On Sunday 12/19/2021 at approximately 8:00 a.m. the operator
completing one of these verification checks discovered that no sodium hypochlorite was discharging into the chlorine
contact chamber. I was serving as operator on call for the week, so he promptly notified me. We began to diagnose the
problem via telephone while I drove to the facility. Upon my arrival, I re -checked the chemical feed valve positions,
which were all correct. We observed that the chemical tank level had not dropped for several hours, so we transferred
additional sodium hypochlorite to the feed tank. At that time, I suspected that potentially the tank level sensor had
failed and the tank may have been empty. We also back -flushed the pump. Upon flushing the pump, a clog of material
was discharged. The sodium hypochlorite feed was restarted at 8:32 a.m. A DPD test of the chlorine contact basin at
approximately 9:00 a.m. indicated chlorine was present.
In an effort to determine the impact of this incident, fecal coliform sampling was promptly performed that morning 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 10:06 a.m. and the test result was 126
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 10:21 a.m. and the test result was 440
cfu/100m1.
• A second downstream sample was taken further downstream at the Armstrong Road Bridge. The sample was
collected at 10:36 a.m. and the test result was 27 cfu/100m1.
When we initially spoke on 12/20/2021, a faulty tank level indicator was thought to possibly be part of the issue. Upon
investigation, including a site visit by the City's SCADA integrator, the level indicator is fully operational and that was not
the source of the problem. As noted above, a clog of residual material was clogging the chemical feed pump and this
appears to be the cause of the pumping failure.
Based on examining SCADA records of when the recorded sodium hypochlorite tank level ceased decreasing, the sodium
hypochlorite feed was not operating properly from approximately 4:00 p.m. on Saturday 12/18/2021 until 8:32 a.m. on
Sunday 12/19/2021. From an evaluation of the flow data for this period of time approximately 471,240 gallons were
discharged without full disinfection.
Thanks,
Douglas Barker
Two Rivers Utilities
Wastewater Resources
Treatment Plant Supervisor
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