OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00305
PWS Name: FOREST GROVE, CITY OF
 
Who Was Contacted: Andy Sewall
Contact Phone: 503-747-9827
Contact Date: 11/24/2021
Contacted By: ALFAFARA, NICOLE (DWP)
Contact Method/Location: Phone
 
Assistance Type: INCIDENT RESPONSE
Reasons: Operations
 
Details: System reached out to DWS Staff on 11/23/21 and 11/24/21 to inform them of a recent turbidity event. On 11/23/21 at 10:21 am the system's streaming current monitor was not reading properly leading to temporary poor coagulation for 25 minutes. A maximum CFE reading of 1.1 NTU and maximum IFE of 0.8 NTU was reported (estimated duration: approximately 10 minutes). Six samples were collected in the distribution system on 11/24/21; turbidity ranged from 0.05-0.10 NTU and chlorine residuals ranged from 0.80-0.95 mg/L.
Given the fact the system was still meeting CT, maximum CFE turbidity was 1.1NTU (<1.49 NTU) and the event's short duration of 25 minutes it was deemed no public notice was needed. The system was directed to check back in with their DWS staff contact on Monday (11/29/21) to review turbidity trend over the weekend,. The system was also directed to report the turbidity event in the monthly SWTR report (with the maximum CFE in the column specifically provided for highest continuous data reading) and were informed the highest of the required 4 hour readings would be considered the daily maximum turbidity for compliance purposes.

11/29/21 Update: There were no additional turbidity exceedances since 11/23/21. Reservoir effluent turbidites were down to 0.034 NTU on 11/29/21. Staff are reflecting on the event and discussing what led to this issue, steps to correct it, and what can be done to prevent in the future issues.


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DBPs :: TOC & Alkalinity :: DBP Sample Sites :: FANLs :: MRDL :: Turbidity :: SWTR :: RAA :: LRAA For SDWIS: 3887