The Portland Water Bureau is recommending the City Council approve the construction of a "granular media" filtration plant on property it already owns east of Oxbow Park to fight contaminents in Bull Run water.
During a Tuesday morning work session, bureau officials stuck by earlier cost estimates for such a plant of between $350 million and $500 million. They will also the council to approve the contracting process next week, but do not need a decision on the type or location of the plant until early 2019.
The council authortized the bureau to pursue contruction of such a plant after cryptosporidium, a potentially deadly parasite, was repeated found in the reservoir in the Bull Run Watersed, the primary source of Portland's water.
During the work session, the council was told that most large municipal water agencies filter their water with mixes of sand and gravel known as granular media. Only a few use membrane or "slow sand" methods, which the officials said were not as satisfactory.
After considering several locations for the plant, the bureau is recommending a 95-acre parcel known as Carpenter Lane. The plant would only need around 35 acres, leaving room for solar panels to help power it, the council was told.
The council will not consider testimony on the type and location of the proposed plant next week, but will schedule a public hearing on those questions before making a final decision. Although water rates will need to be increased to pay for the plant, how much will not be known until then.
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