OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 91964 | ||
| PWS Name: | CAMP YAMHILL | ||
| Who Was Contacted and Phone: | CALEB COLE ( 50) 366-2331 | ||
| Contact Date: | 01/27/2017 | ||
| Contacted By: | CIVIL WEST ENGINEERS, INC (DWP) | ||
| Contact Method/Location: | Field | ||
| Assistance Type: | CIRCUIT RIDER ASSISTANCE | ||
| Reasons: | N/A N/A |
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| Details: | SUMMARY: Tracer Study DETAILS: The circuit rider was contacted by Evan Hofeld of the Oregon Health Authority on 1/27. Mr. Hofeld requested a tracer study be done as the water system was operating using a CT based on an estimated contact time. The system has an unusual disinfection system where chlorine is injected into a recirculation pump that is plumbed into the clearwell. We coordinated with the staff at Camp Yamhill for a visit to further assess the system to help in development of a tracer study methodology. We chose to test the system as is and treated the clearwell/recirculation pump as a continuously mixed tank. The tracer study was done and yielded a contact time of 3.5 minutes. At the time of the test the pH meter was reading 8.0, and the temperature was 47.3°F. The plant typically runs a concentration of 2.3 ppm of sodium hypochlorite. For a 1.0 log giardia inactivation at these parameters the contact time should be a minimum of 36.5 minutes. ACTION NEEDED: It is recommended that an analysis be done to determine alternative means to extend the contact time to achieve acceptable CT.It is also recommended that the control/monitoring meters be calibrated, as a pH of 8.0 for a surface water source similar to the North Yamhill River would be expected to be much less than 8.0. This high pH will require a much longer contact time, so it is critical that an accurate value can be used for design. | ||