Portlanders will pay more for their water after the City Council on Wednesday chose the most expensive option for a new treatment plant needed to meet state and federal rules.

Homeowners are expected to pay an average of $10.38 more per month over the next 16 years for the filtration treatment plant approved unanimously by the council. The total cost is forecast at $350 million to $500 million. Construction is expected to take at least a decade.

State health officials previously exempted the city from a federal requirement to treat its water for the parasite cryptosporidium. But the exemption ended after the city detected high amounts of the organism in the Bull Run watershed this winter. The reservoir near Mount Hood supplies most of Portland's drinking water, historically with almost no treatment.

The city considered building a facility that would use ultraviolet light to kill parasites. That would have cost $105 million and kept rate increases smaller in the short run.

But UV treatment doesn't protect water against other pollutants such as lead. And the Portland Water Bureau predicted two factors could require more cleaning of Bull Run water in coming decades. First, regulations could tighten. Second, climate change could create landslides that dump mud into Bull Run, fires that drop ash on the watershed, as well as algae blooms.

Finally, water bureau officials said a UV plant would need to be updated or replaced in 25 years.

Those factors could force the city to build a filtration plant eventually, after already having spent money on the UV plant.

A water bureau risk analysis presented to the council Wednesday brought a consensus among the council and stakeholders who testified that filtration would be the more responsible long-term approach for public health, city budgeting and mitigating future risks.

The water bureau attached probabilities to all those risks, and the city's chief financial officer said the results suggested filtration "may be the most cost effective option."

Mayor Ted Wheeler agreed.

"We've settled on the most challenging solution, but it's also the most responsible solution," Wheeler said.

But some members of the public testified in opposition. Public testimony largely opposed the city treating the Bull Run water at all. Some criticized the Environmental Protection Agency rule concerning cryptosporidium as out of date. They noted that animal-borne strains of the parasite are not harmful to humans, and critics have said it's unlikely the Bull Run contamination was human-caused.

Others said the city was moving too fast.

"Our chief concern is decisions with long-term impacts on the people of Portland are being made in a rush based on fear," said Theodora Tsongas, a former environmental epidemiologist with the Oregon Health Division.

The Portland Business Alliance also spoke against the plan, asking the city to build an ultraviolet plant for now and replace it with a filtration system later. That would save ratepayers money in the near term.

In 2006, federal rules required cities with unfiltered water systems to treat for cryptosporidium, but the Oregon Health Authority permitted Portland an exemption so long as its water bureau regularly tested for cryptosporidium and found none.

The water bureau exceeded parasite limits set by the state variance after it found excessive amounts of the cryptosporidium parasite from January to March. It found a total of 19 of the parasite's microscopic structures called oocysts in 14 tests, which meant it surpassed the state's limit of finding one oocyst per 13,300 liters of water in one year.

The council originally planned to pursue a combination of treatment options in order to quickly comply with state rules and limit near-term rate increases.

"I came to this conversation with an open mind," Water Commissioner Nick Fish said. "We need to think 100 years and not 20 years forward."

Commissioners voted on a treatment option, despite requests from members of the public who asked that the council plead for more time from the Oregon Health Authority to consider the long-term health and financial impacts of their decision.

The Oregon Citizens' Utility Board and the Portland Utility Board, local ratepayer advocacy groups, also expressed "grave" concern over the rushed timeline-- although they also said they would support filtration if the council was unable to win a delay.

The Portland Utility Board had proposed a delay until the end of the year.

"The city should not be rushed into a decision and should attempt to minimize both uncertainty and risk," Portland Utility Board co-chair Colleen Johnson said.

The state health authority originally gave the city an August 11 deadline to come up with a plan when it told the water bureau in a May 19 letter that it would revoke the city's exemption from federally-mandated water treatment.

The state agency on Tuesday granted the city a 60-day extension for when water bureau officials had to submit a plan to comply.

One rationale for building an ultraviolet treatment plant was speed. It would have taken only five years, whereas a filtration system will take 10 to 12 years to build.

But Multnomah County Public Health Officer Paul Lewis said the city can afford to take its time. He noted that the county saw fewer cases of cryptosporidium-related illnesses than average this year, which suggested the immediate risk to public health is limited.

"We shouldn't rush to do UV, which is really just a one-trick pony," Lewis said.

Council members said they were persuaded by the water bureau's forecast of the risks that the city faces if it doesn't build a filtration plant that can treat a wide variety of pollutants.

"I'm at the point where filtration makes the most sense to me because it actually will solve problems that are very likely to come in the future," Commissioner Chloe Eudaly said.

Eudaly did not support filtration initially, she said. As a native Portlander, she said she "doesn't relish the thought of the taste or quality of our water changing."

She agreed with some members of the public who said cryptosporidium isn't necessarily a health problem. But she said exposing the city to daily $1,000 fines and future injunctions by failing to comply with the federal rule would be irresponsible.

Eudaly expressed serious concern for low-income ratepayers, but Fish assured her and the public that the water bureau would do everything it could to mitigate costs for them. Fish took to Commissioner Amanda Fritz's suggestion to look for projects that could be delayed to help ease cost increases.

"You have my complete commitment," Fish told Eudaly.

Fritz supported the treatment decision only after Fish assured her the water bureau would engage robustly with both utility boards and the public as they put together their treatment plan for the state.

In his closing remarks, Wheeler acknowledged a tension in the room felt by opponents and proponents of treatment.

"There is a sadness that goes along with this decision," Wheeler said. "We're leaving part of our hard-fought past behind. It is the right decision, it is the responsible decision, and it is the best decision for this community."

Note: This story has been updated to more accurately reflect the Oregon Citizens' Utility Board's position and the city's compliance with state requirements. The ratepayer group criticized the city for rushing a treatment decision but did not advocate an extended timeline. The city exceeded parasite limits set by the state health authority, but did not fall out of compliance with a state exemption.

--Jessica Floum

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