OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00279
Who Was Contacted: Dave Stone
Contact Phone: 503-630-8270 (Email address hidden)
Contact Date: 03/04/2020
Contacted By: NUSRALA, JAMES (DWP)
Contact Method/Location: Phone
Reasons: SWTR
Details: System did not meet disinfection CTs February 19, 20 and 21. System was filling a distribution reservoir that had been offline with a higher demand flow through the two clearwells. As a result CT required was around 56 to 58 for a 1.76 mg/L chlorine residual, pH of 7.3, and temp of 6.7 degrees C. CT achieved for the high flow with 29 minutes of contact time from new tracer study was around 51 at this chlorine residual. As a result, City will issue a tier 2 public notice with the March water bills to all customers. Dave forwarded a draft copy of notice for DWS review. In the future, City will increase chlorine residual to near 2.0 mg/L with higher flows in cold temperature conditions to ensure CTs are met. City also looking at replacing clearwells with more baffled contact reservoirs, with hopefully greater contact time through a new tracer study. Disinfection requirements met since Feb 21, with lower flows and residuals around 1.65 mg/L.
Action required: City to issue public notice in March with Copy to DWS. DWS to review March CT report before requesting a return of violation to compliance.
4/9/20: Dave emailed over a copy of the public notice that was approved and sent out with March bills to all users, on 3/20. Also, I have reviewed March's CT report. CTs were calculated appropriately and CTs met at all times. Chlorine residuals up around 1.6 mg/L for the whole month.

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