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OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 00657 | ||
| PWS Name: | PORTLAND WATER BUREAU | ||
| Who Was Contacted and Phone: | Chris Wanner (503) 823-9999 | ||
| Contact Date: | 08/31/2010 | ||
| Contacted By: | SALIS, KARI (DWP) | ||
| Contact Method/Location: | Office | ||
| Assistance Type: | OTHER REGULATORY - REGULATORY ASSISTANCE | ||
| Reasons: | Coliform Operations |
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| Details: | SUMMARY: frequency of TC+ DETAILS: Chris Wanner, Mike Sheets, and Yone Akagi asked to meet with Dave Leland, Chris Hughes, and Kari Salis to discuss the frequency of total coliform detections. They switched to the Colilert method in October 2007, and have since seen many more TC+, since this method is more sensitive to TC+. Sampling from open reservoir outlets represents about 22% of their samples overall, but accounts for 70% of TC+. They have seen a correlation between Temperature and TC+, so are worried for late summer / fall. Increasing the chloramine residual has not been shown to help. They are hoping to take Res 3 and 6 off-line sooner than the approved schedule, if operational problems can be solved. They are not worried about exceeding the TC MCL, but they are concerned about how to know what represents a public health issue or not. The rule is such that an EC+ and a TC+ follow up, or two EC+ requires a boil notice. In some cases there may be two unconfirmed positives that are unrelated. If PWB can demonstrate this with reasonable certainty, DWP can look at these situations on a case-by-case basis. We also talked about repeat sampling near the reservoirs, and how an "upstream" repeat location is not very meaningful, so DWP recommends their 2 repeat locations be taken downstream, in addition to the same site. Their sampling plan is being re-written to reflect this. Also, if they wish to have non-potable water in Res 3 and 6, an air gap would be needed. ACTION NEEDED: none | ||