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OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 00124 | ||
| PWS Name: | FISHHAWK LAKE RESERVE AND COMMUNITY | ||
| Who Was Contacted and Phone: | Jim Dahlquist (503) 755-2132 | ||
| Contact Date: | 10/03/2011 | ||
| Contacted By: | NUSRALA, JAMES (REGION 1) | ||
| Contact Method/Location: | Office | ||
| Assistance Type: | WATER QUALITY ALERT RESPONSE | ||
| Reasons: | Disinfection Byproducts N/A |
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| Details: | SUMMARY: Response to TTHM detection > MCL DETAILS: 9/21/11 DBP sample was 0.0845 mg/L TTHM, exceeding the MCL of 0.080 mg/L. First exceedence of the MCL value at system. I explained to Jim that compliance with MCL is based on running annual average of 4 quarters of monitoring for TTHM. Jim indicated that higher DBP levels directly a result of increasing chlorine dose at water plant after May 2011 tracer study indicated less contact time available than was estimated using earlier figures. System had been targetting a 1.0 ppm residual leaving plant since May 2011, up from 0.7- 0.8 ppm. I correlated earlier lower DBP values with lower chlorine residuals in system-chlorine dosages at plant in 2008-2010 roughly have of 2011 values, with 2008-2010 DBP levels about half of 2011 values. Jim and I discussed lowering chlorine dose at plant as CT achieved is roughly double CT required. DWP to see if lowering dose, and take a follow up sample for TTHM and HAA5 and see if lowering dose brings down DBP levels. ACTION NEEDED: Jim to immediately begin lowering the chlorine dose at plant. System will closely monitor usage in system and corresponding chlorine residuals at plant and in system, and take follow up DBP sample during October 2011. DWP to evaluate need for continued quarterly monitoring after October dual sample set for TTHM and HAA5. | ||
| Associated Alerts: | CHEM5071 - 10/03/2011 - TTHM |
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