OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00317
Who Was Contacted: Greg Benthin
Contact Phone: 503-897-2669 (Email address hidden)
Contact Date: 07/03/2019
Contacted By: BAIRD, GREGG (DWP)
Contact Method/Location: Phone
Assistance Type: OTHER WATER QUALITY - Total Microcystins detection in entry point sample
Reasons: Cyanotoxins
Details: DWS was informed today 7/3 that the City of Gates’ entry point (EP) sample collected Monday 7/1/19 preliminary result is 0.36 ug/L for total microcystins in the finished water which is above the health advisory level for vulnerable populations (note: raw water sample collected the same day was 1.76 ug/L). A confirmation sample must be collected from the EP within 24 hours and begin daily entry point monitoring. Gates has arranged with the DEQ lab to collect a confirmation sample tomorrow 7/4 and drive it up by 10am. Analysis will begin Friday 7/5 with results available Monday 7/8. The requirement to issue an advisory is based on the results of the confirmation sample. The city is not issuing a voluntary advisory at this time and will wait for the results of the confirmation sample. Note: the 7/1 EP sample was collected from a tap just past the point of chlorination but prior to the pipe used for disinfection contact time which is not the correct sampling location. The confirmation sample will be collected from the proper EP location (1st user tap, after adequate disinfection). Steps to optimize treatment plant operation for cyanotoxin removal were discussed and the city will increase the chlorine residual to 2 ppm to increase CTs for disinfection of Microcystins. UPDATE: Fri. 7/5 DEQ lab reported the EP confirmation sample result as non-detect (ND). Since initial EP sample was not confirmed, no advisory is required. Collecting the confirmation sample at the proper location (post disinfection), along with the treatment changes Gates was able to do prior to collecting the confirmation sample (increase chlorine) may have positively impacted this sample result. Gates will continue daily EP monitoring over the weekend and deliver samples from Fri/Sat/Sun/Mon to the lab Mon. 7/8. If two daily EP samples are ND, they can return to weekly EP monitoring.

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