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UPDATE: Mayor and commissions make no decision after being briefed on different ways to treat potentially deadly parasite in Bull Run water

PORTLAND TRIBUNE FILE PHOTO - The Bull Run reservoir holds the drinking water supply for Portland and several suburbs. Bull Run water is considered relatively pristine, but has been found repeatedly this year to contain cryptosporidium, a potentially harmful parasite.
The City Council made no decision Tuesday morning after being asked by the Portland Water Bureau officials to consider spending between $105 million and $500 million to treat a potentially deadly parasite in the Bull Run Watershed.

Mayor Ted Wheeler and the other members of the council were concerned about the affect on water ratepayers who will pay for either option.

An Aug. 2 council hearing has been tentatively scheduled for the decision, which must be made by Aug. 11.

The June 27 work session was scheduled after the Oregon Health Authority announced it will revoke the city's variance from federal rules requiring treatment for cryptosporidium on Sept. 22. Portland owns and operates the only large municipal water system in the country that does not currently treat for the parasite.

Bureau officials will testify that the city could build a plant that treats crypto — as it is commonly called — with ultraviolet light for $105 million. Such a plant would not treat or filter any other contaminant out of water in the Bull Run reservoir, the city's primary source of water that also is sold to suburban customers.

A filtration plant could be built for between $300 million and $500 million. In addition to removing crypto from the water, such a plant also could filter out contaminants that might be prohibited by the federal government in the future. Although none are currently under discussion, regulations have changed many times in previous years.

The vast majority of U.S. cities built filtration plants to comply with earlier EPA requirements that also meet the crypto rules.

Such a plant also could filter sediments out of the reservoir, such as dirt and mud that enter the reservoir because of landslides triggered by an earthquake. It also could filter ash deposited by a catastrophic wildfire in the watershed. Such a fire is overdue. They are thought to occur every 350 years, but the last one happened 524 years ago in 1493.

The City Council fought complying with the rule adopted by the U.S. Environmental Protection Agency for many years, because Bull Run water historically has been so clean. It is currently only treated with chlorine and ammonia. The OHA granted a variance in March 2012, provided the city regularly test for crypto and report its findings. None was found after that — until earlier this year, after heavy winter storms may have washed it into the reservoir.

Once the city realized it could no long comply with the variance, it notified the health authority, which enforces the variance for the EPA. The health authority announced the revocation on May 11. It has given the city until Aug. 11 to submit a plan with measurable mileposts for complying with the rule by treating Bull Run water for crypto.

Planning for a UV plant is much further along than planning for a filtration plant. When the council decided to pursue the variance, it also directed the bureau to draw up plans for a UV plant. They are so complete construction could be finished in five years. Planning for a filtration plant would have to start from scratch and construction could take 10 to 12 years, the Water Bureau says.

There are no estimates yet on the impact of either project on potential water rate increases.

Crypto is transmitted through animal feces. It can cause cryptosporidiosis, a respiratory and gastrointestinal illness, which killed 104 people and sickened thousands of others in 1993 in Milwaukee, Wisconsin. That outbreak prompted the EPA to adopt its treatment rule.

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