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DMR note: "RW with <0.5 mg/L of total chlorine distributed over 109 minutes because of divert-to-drain failure. On Sunday June 2, 46,270 gallons of RW with a total chlorine residual of <0.5 mg/L was distributed (via York Pump Station) over 109 minutes. The incident was the result of a faulted PLC card at York Pump Station which did not allow the control system to divert RW when its Cl2 level dropped below 0.5-mg/L. The faulted PLC generated an alarm, which staff noted at the time of the alarm. The Control System indicated that the control valves for the RW system at York PS were operating normally in automatic control. Staff were unaware that the PLC fault caused the loss of control of the RW Distribution Valve until June 3 when the distribution valve failed to divert when it received a divert-to-drain signal. An operator was dispatched to the site and closed the distribution valve locally, and an instrument technician subsequently reset the PLC card which restored control over the distribution valve.
To prevent this event from reoccurring, the alarm description for the PLC fault has been modified to clearly indicate that it applies to the York Pump Station. Additionally, a new alarm has been added that will be generated if there is RW distribution flow when the total residual is <0.5 mg/L." Jankowiak: conducted inspection following this in June. Recommend warning letter for violation. Decision: warning letter. This is a new permit condition that they are adapting to. The effluent was fully disinfected, the chlorine is for maintaining the line. Steps taken to correct/prevent. Send Warning letter.
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