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OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 00414 | ||
| PWS Name: | JOSEPH, CITY OF | ||
| Who Was Contacted and Phone: | Jim Lewis (541) 432-3832 | ||
| Contact Date: | 08/28/2007 | ||
| Contacted By: | WILSON, BOB (DWP) | ||
| Contact Method/Location: | Field | ||
| Assistance Type: | CIRCUIT RIDER ASSISTANCE | ||
| Reasons: | N/A N/A |
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| Details: | SUMMARY: System needs tracer study DETAILS: I Met with Jim Lewis on August 14, 2007 to conduct a chlorine contact time tracer study. After the chlorine feed was boosted, the system’s Hach DR 700 Chlorine test kit was used to check residual every few minutes at the first user. In this case, the first user was the sample tap in the control room which is immediately off the transmission pipe from the reservoir to the distribution system. At the beginning of the study, chlorine residual at the first user was 0.36 mgl. The reservoir level started at 18.9 feet and dropped to 16.1 feet during the study, and the average flow for the entire study was 1135 gpm. After several hours with the boosted chlorine feed, the residual equalized at 0.58 mgl. The C10 or increase of 10 percent of the boosted level was reached at 275 minutes. An additional 2 minutes can be included for contact time in 113 feet of 16 inch diameter transmission piping before the actual user. This result in a total of 277 minutes of chlorine contact time. ACTION NEEDED: The City of Joseph should immediately begin using 277 minutes for contact time when computing their daily CT value. As an alternative, when the reservoir volume is greater or flow is less that the study, a baffling factor for reservoir efficiency of 45 percent can be used. | ||