OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00893
Who Was Contacted and Phone: Tim Lyda (503) 812-8802
Contact Date: 09/19/2011
Contacted By: KALISH, FRED (REGION 1)
Contact Method/Location: Office
Reasons: Operations
Details: SUMMARY: Malfunction of Filter #1 Effluent Control Valve DETAILS: Tim called this morning to report an apparent malfunction of the effluent control value of Filter #1. On Saturday night (2100) this past weekend, the operators received autodial alert of CFE turbidity (>0.3). Within 45 minutes the WTP was turned off. In reviewing the SCADA data it was discovered that the effluent control valve had failed to throttle down after an initial 5 minutes of FTW. The reason for this failure is unknown at this time. The result was that the effluent valve allow more flow out of the filter than entering the filter (650 gpm), resulting in the water level in the filter dropping below the bed and resulting in stirring up the filter bed and releasing high turbidity, inadequately filtered water from the filter. The IFE readings by the SCADA is limited to a max of 0.5 NTU. The CFE at this time over a ten minute period peaked at 20 NTU (its upper limit) for a short time and returned to below 0.3 NTU before 10 minutes had passed. The WTP had autoshutoff set at 0.3 NTU for greater than 10 min - this was never reached. It concluded that for something less that 10 min, a flow of 1300 gpm (max) at an undetermined spike of NTU (>20 NTU) entered the 1.1 MG Reservoir (= disinfection contact tank). A tracer study conducted in 2005 showed a 115 minute contact time - so it is concluded that none of the contaminated water left the 1.1 MG Reservoir - it has been "off-line" since Saturday. Since the reservoir may contain unfiltered water with possible contaminants (e.g., cryptosporidium) the water will be wasted from the reservoir and the reservoir thoroughly cleaned and rinsed before being returned to service. IN the interim, the City will use its groundwater wells and storage from its 1.9 MG reservoir. The WTP will not be operated during this period. ACTION NEEDED: Wait to hear from Tim.

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