OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00497
Who Was Contacted and Phone: Bob Klein (503) 435-3103
Contact Date: 12/04/2015
Contacted By: HOFELD, EVAN (DWP)
Contact Method/Location: Office
Reasons: Disinfection Byproducts
Details: SUMMARY: DBP and TOC Reduction Granted DETAILS: I received a request on 11/12/15 from Bob Klein to grant a reduction in DBP sampling from 4 paired (TTHM and HAA5) DBP samples per quarter to 2 paired samples per quarter and TOC monitoring from monthly to quarterly. A paired DBP sample is one in which both HAA5 and TTHM are analyzed. The monthly sampling from October 2014 through September 2015 indicates the highest TOC result was from October 2014 with raw water TOC of 1.97 mg/l and treated water TOC of 0.94 mg/l. The locational running annual average (LRAA) for both total trihalomethanes (TTHM) and haloacetic Acids (HAA5), were also below half the MCL. As a surface water system serving 32,535 people, McMinnville’s TOC and alkalinity sampling schedule was approved for a reduction from monthly to quarterly. The DBP sampling was reduced from 4 paired DBP quarterly samples to two paired samples taken once quarter in the months of October, January, April, and July of each year. Under this new schedule a paired DBP sample must be taken from the 2DBP-01 FAA, Airport - 10 sample site (the site with the highest historical TTHM results) and a second paired DBP sample must be taken from the 2DBP-04 Morgan Ln - 16 site (the highest historical HAA5 site). I sent a letter to the system dated December 4, 2015 to this effect. ACTION NEEDED: System to begin reduced sampling schedule as indicated above, starting with TOC in 4th quarter 2015 and DBP with 1st quarter 2016. To remain on reduced monitoring results must demonstrate LRAA and TOC levels less than or equal to the following limits: 1) TTHM LRAAs of 0.040 mg/L at all locations-- 2) HAA5 LRAA of 0.030 mg/L at all locations-- and 3) Annual average raw and filtered water TOC of 4.0 mg/L. If the DBP requirements are not met, routine monitoring must be resumed in the next quarter after exceeding the above specified LRAA levels.

More information for this water system: SDWIS ID 4686
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