OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00657
Who Was Contacted: Yone Akagi
Contact Phone: 503-823-7648
Contact Date: 10/12/2021
Contacted By: GENTRY, CARRIE (DWP)
Contact Method/Location: Phone
Assistance Type: PLAN REVIEW
Details: Yone Akagi, David Peters, Jude Grounds, Lyda Sykes, Mark

Met with PWB to review their 30% plans for the new filtration treatment on Carpenter Lane. They will be using rapid sand filtration, starting at 6 gpm/sf and going up to 10 gpm/sf within a year as approved based on a pilot study. The WTP capacity will be 135 MGD and will recycle the wash water at a maximum 5% percent of total flow. The clearwell will be 6.6 Million gallons (two cells, 3.3 MG each). The tanks will be buried with a sloped roof, perimeter drains, water-proofing, and leak detection. They will generate sodium hypochlorite on-site from salt, ozonate prior to sedimentation, and increase pH and alkalinity, then decrease pH with carbon dioxide. They plan to provide at least 0.5-log giardia inactivation after filtration through chlorination. At startup, they will only be able to shut off at headworks so are designing several overflow options at the Carpenter lane site. We discussed reporting and that along with final plans due October 31, 2022 they will also need to submit a construction schedule. We will have further conversations about the level of detail needed. We discussed operator certification and getting operators the experience in order to be certified at the appropriate level on Day 1. Also at start up they will need to have piping for both the unfiltered source and the filtered water. We discussed that only filtered water can go into the distribution system starting on Sept 30, 2027.

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