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OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 00799 | ||
| PWS Name: | SEASIDE WATER DEPARTMENT | ||
| Who Was Contacted and Phone: | Ben Davis (503) 738-5112 ext. 214 | ||
| Contact Date: | 09/08/2009 | ||
| Contacted By: | HOFELD, EVAN (REGION 1) | ||
| Contact Method/Location: | Office | ||
| Assistance Type: | OTHER REGULATORY - REGULATORY ASSISTANCE | ||
| Reasons: | SWTR Operations |
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| Details: | SUMMARY: CT Calculations DETAILS: Ben Davis called to discuss calculation and reporting of CT. He said that they would use the peak flow during a 24-hr period to calculate contact time, but since their lowest chlorine residual during that same 24-hr period is just as the plant is turned on after being shut down over night due to a 48 minute sampling delay in their on-line post clearwell analyzer, they would calculate their actual CT using the lowest chlorine during the 24-hr period, excluding the first 48 minutes. I told him that this was reasonable and an acceptable method for calculating CT. He said he would use the highest chlorine residual and pH, and lowest temperature to determine required CT. ACTION NEEDED: Calculate CT daily using data gathered within a consistent 24-hr period (10:30 am - 10:30 am), each day the plant is operating. Use the peak flow within that 24-hr period to calculate contact time and the lowest chlorine residual recorded within that 24-hr period, excluding the first 48 minutes, to calculate CT achieved. Use the highest chlorine residual and pH, and lowest temperature within the 24-hr period to calculate required CT. | ||