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OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 00552 | ||
| PWS Name: | BRIDGE WATER DISTRICT | ||
| Who Was Contacted: | Daniel Horner | ||
| Contact Phone: | 541-290-9661 | ||
| Contact Date: | 01/28/2020 | ||
| Contacted By: | PARRY, BETSY (DWP) | ||
| Contact Method/Location: | Phone | ||
| Assistance Type: | INCIDENT RESPONSE | ||
| Reasons: | SWTR |
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| Details: | I learned today that heavy rains earlier in the month had overwhelmed their new slow sand filters (put online in September 2019). In early January, heavy rains for a couple days led to rising levels of treated water turbidity. When it reached 4.8 NTU, they shut the plant off and ran on stored water for 4-5 days. Raw water turbidity was not measured during this period. While using only stored water, the water coming from the filter continued to rise and peaked at 12 NTU. Days later when they put the filters back online (stored water running out), the turbidity was ~4.0 NTU. The turbidity has decreased since then but even today, some two weeks later, it is just under 2.0 NTU. As designed, their UV reactor shut down automatically when the turbidity got too high. Daniel Horner cleaned the sensor or the tube as needed and got it running again. Their treatment plant designer, Rob Henry of HBH engineering, will email Daniel in trying to figure out what led to this and what to do now. Rob wonders whether this is a rare event, or if it will happen a couple times a year. If it is recurring, Rob might suggest adding a prefilter (an auto-backwashing media filter, roughly $2,000), which worked well for another small rural system with slow sand filtration. Daniel is also thinking of valving off one or two of the spring sources with the dirtiest water in winter, when they have less demand. I suggested he would probably need to visit the springs during a high turbidity event to get the full perspective on that. Another option is adding more storage to outlast these storm events, and that would help them in summer low flows as well. There will be a Tier 2 treatment technique violation for January because >95% of turbidity readings during plant operations will exceed 1.0 NTU. I told Daniel I would get back to him with the public notice template once the January treatment report has been filed. |
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