OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00213
Who Was Contacted: Ray Doan
Contact Phone: 541-396-4286
Contact Date: 10/21/2021
Contact Method/Location: Field
Details: Background/Problem Identification:

Casey Lyon reached out to Civil West on September 22nd, 2021 and said that the City of Coquille and a small purchasing system of Coquille (Dean Minard), recently exceeded the disinfection by products (DBP) MCL for TTHM’s.

The City of Coquille provides conventionally treated water to 1,963 connections drawn from the Coquille River during the dry season and Rink Creak during the wet season.

Assistance Provided:

A site visit to the water system was made on October 19th, 2021. From the information gathered, the following operational mitigation measures may help to reduce DBP levels at the City of Coquille:

•Eliminate pre-chlorination
•Adjust overall chlorination residual to provide just enough residual to meet CT and maintain the required residual in distribution
•Inject pH control (soda ash) post-clearwell versus pre-clearwell to allow a lower pH in the disinfection segment (clearwell)
•Start a flushing program throughout the distribution system
•Reduce contact time within the reservoir tanks as much as possible while maintaining sufficient storage to provide fire-suppression

Follow-Up Actions Needed:

The circuit rider is available to assist further as needed.

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