OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details
PWS ID: OR41 00821
PWS Name: SILETZ, CITY OF
 
Who Was Contacted and Phone: Allen Middaugh (541) 444-2521
Contact Date: 02/06/2007
Contacted By: POTTS, JOHN (DWP)
Contact Method/Location: Field
 
Assistance Type: CIRCUIT RIDER ASSISTANCE
Reasons: N/A
N/A
 
Details: SUMMARY: Turbidity profilling and CT calculation assistance DETAILS: I conducted a turbidity profile on filter 1. The WTP is a US Filter clarifier package plant with two 175 gpm filters. The filter had run for 1020 minutes, with a maximum filter run typically 1440 minutes. Raw water entering the plant was 0.85 NTU and filtered effluent for 1 was 0.029 NTU at the start of the study. I used the Hach 1720D in line turbidimeter for filter 1 as the monitoring turbidimeter. There was a 30 second delay in the water reaching the unit from the filter effluent line. The initial turbidity reading as 0.029 NTU at the start of the filter to waste cycle. The filter to waste cycle ran for 5 minutes and the turbidity level reached 0.053 NTU at that time. All filtered water after the filter to waste cycle was dumped into the clearwell. The peak turbidity level observed was 0.135 NTU at 9 minutes. I ran the profile for 60 minutes and the turbidity at that time was 0.054 NTU. I prepared a profile graph and mailed it to Allen for his record and reminded him that both filters need turbidity profiles conducted and recorded quarterly. I reviewed the daily CT calculations and discovered that the operators were using the 1.0 log inactivation column when they should be using the 0.5 inactivation column since the WTP is granted a 2.5 log removal credit based on the last sanitary survey. I told them to put a note in the Feb SWTR indicating the change in calculations and what it was based on. I also notified Karen Kelley of my findings ACTION NEEDED: None unless requested

More information for this water system: SDWIS ID 3993
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