OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details
PWS ID: OR41 00548
PWS Name: CLARKS BRANCH WATER ASSOC
 
Who Was Contacted and Phone: Mary Gouin (541) 863-7221
Contact Date: 06/11/2013
Contacted By: CREMENT, BRADLEY (DWP)
Contact Method/Location: Field
 
Assistance Type: CIRCUIT RIDER ASSISTANCE
Reasons: N/A
N/A
 
Details: SUMMARY: Enhance Contact Time DETAILS: Clarks Branch Water Association (CBWA) owns & operates a community WS serving 140 people through 80 connections. Water supplied by S Fork of the Umpqua River where it is pumped to an ECI package plant. Treatment includes flocculation, sedimentation, single mixed media filter, disinfection & a 3,000 gallon clearwell. In addition to the clearwell, there are four (4) horizontal steel storage tanks located outside treatment plant provide storage & additional contact time. A previous contact study was performed (in 2006) by the circuit rider who found a contact time of 36-minutes at the peak production rate of 60 gpm. Given this was significantly lower than the 200-minutes of contact time that was historically used-- CBWA again contacted the circuit rider to request another tracer study. Met with operators on-site to evaluate a new CT study taking advantage of their pre-chlorination segment (which was ignored in the first study). During the visit, I agreed with the methodology of the first test, & made the operators aware there was no reason to re-test except to add in the pre-chlorination segment. However, they had no ability to test the residual of the pre-chlor segment before it was boosted by the post-chlor in the clearwell. We determined location of a sample point for the operators to start monitoring to establish a pre-chlor residual level. After testing was performed for a few weeks, the operators discovered there was a zero residual level on their pre-chlor segment. They tried boosting the pre-chlor dosage to get a residual, but the chlorine demand on the raw water was much higher than they were comfortable adding. ACTION NEEDED: None, they have decided to keep pre-chlor levels low and investigate modifying their tank configuration to increase contact time. Once tanks are reconfigured a new test will need to be performed.