Rare tour of Bull Run watershed inspires people who want to know more about Portland's drinking water

Portland's drinking water comes mostly from two reservoirs in the Bull Run watershed near Mount Hood, tapping streams that run through more than 100-square-miles of thick forest. The city also ships Bull Run water to suburbs from Gresham to Beaverton. The gauge measures water levels. Jamie Francis | The Oregonian/OregonLive

Portland's water bureau detected a trace amount of cryptosporidium parasite in a test of drinking water from the Bull Run watershed again Monday.

After four straight years not finding any cryptosporidium during weekly water samplings, the city has now detected the parasite four times this year, raising the specter that the city might have to build an expensive treatment plant.

This week's finding does not raise immediate alarms for human health, officials said. The Portland Water Bureau "does not believe there is any increased public health risk" but recommends that people with weak immune systems consult their doctors about drinking water, bureau officials wrote in a press release.

Four positive tests in five weeks is striking, officials noted. "This is the most cryptosporidium we've detected in more than a decade," said Yone Akagi, the bureau's water quality manager.

Unlike in most other cities, Portland's water bureau does not treat its water for cryptosporidium, a parasite found in animal and human waste. The bureau received an exemption in 2012 from the Oregon Health Authority to forgo treating for the pathogen after the water bureau found no cryptosporidium from 2002 and 2012. Portland opted instead to monitor for the microorganism through regular testing.

Humans are barred from the Bull Run Watershed, making animal scat the most likely source of the parasite, Akagi said.

The state could revoke Portland's exemption if the water bureau finds more than one oocysts--a hard structure found in feces but too small to see--per 13,300 liters of water in one year.

That could force the bureau to build an ultraviolet treatment plant, expected to cost at least $89 million, according to water bureau planning documents. The city could also build a filtration treatment system that would filter out sediment in addition to microorganisms, but that could cost around $300 million, said Edward Campbell, director of resource protection at the water bureau.

Whether or not the bureau will have to build the treatment depends on what future tests reveal.

"The numbers will tell us the tale," Campbell said.

A positive test for cryptosporidium on Jan. 2 required the bureau to increase its testing from two tests per week to at least four times per week. The increased testing will continue at a rate of about 250 liters per week. The bureau plans to sample even more water than required to help make sure the rate of positive tests complies with the conditions under which Portland received its exception, technically termed a variance.

"We're going to have to start thinking about what our treatment options are if we get the variance revoked," Akagi said.

Even if the bureau's tests continue to meet requirements, a tightening regulatory environment could later require Portland to build a treatment plant, bureau director Mike Stuhr said.

"At some point in the future, I expect the city will have to build a treatment plant," Stuhr said.

Commissioner Nick Fish manages the Portland Water Bureau. He said it is "irresponsible" to consider the potential costs of building a treatment plant since the city is currently in compliance with the variance.

"That's not part of any current discussion," Fish said. "It is very unlikely that that is going to happen. Our water is safe."

Note: This story has been updated to reflect the correct spelling of Yone Akagi's name in the second and third references.

--Jessica Floum

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