OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00055
Who Was Contacted and Phone: Gary McLauchlin (503) 325-3524
Contact Date: 01/26/2010
Contacted By: HOFELD, EVAN (REGION 1)
Contact Method/Location: Office
Reasons: Disinfection Byproducts
Details: SUMMARY: DBP Alert DETAILS: Gary called regarding a recent individal result that exceeded the HAA5 MCL. The running annual average was less than the MCL. I told him that they would have to repeat the public notice if the running annual average went over the MCL. He wondered why the result would still be high, even with one of the two open reservoirs covered. I e-mailed Gary the following information: When the MCL for HAA5 was first exceeded, Rob Henry (HBH), conducted an evaluation in 2005 and identified the open reservoirs as a likely contributor. Since LT2 required that the reservoirs be covered anyway, this was a logical first step. If the DBP levels continue to be high after the reservoirs are covered, it may be because, either TOC levels are naturally increasing or another possibility is that due to the declining media levels in the slow sand filters, TOC removal has been diminished (removal of TOC is expected to be between 5-25% for standard slow sand filtration). I attached a summary of a study conducted in New England for evaluating DBP precursor removal processes in slow sand filtration found on-line at: http://www.unh.edu/erg/wttac/non-aligned_treatment.htm. ACTION NEEDED: Re-sand slow sand beds as needed, continue with covering the remaining reservoir, and monitor DBP levels to be alerted if the RAA MCL is exceeded and issue public notice as needed.
Associated Alerts: CHEM3908 - 01/19/2010 - TOTAL HALOACETIC ACIDS (HAA5)

More information for this water system: SDWIS ID 3873
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