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Experts: Risk low that parasite in city reservoir will sicken someone.

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.State and local health authorities want those who drink Bull Run water to believe that it is safe, despite the previously discovered presence of a parasite that has alarmed the U.S. Environmental Protection Agency when found in other supply systems.

At the same time, Dr. Paul Cieslak, the Oregon Health Authority's medical director of communicable diseases, cannot guarantee no one will ever get sick from drinking it.

"While we can never say that with 100 percent certainty, we think the risk is very low," says Dr. Paul Cieslak, the Oregon Health Authority's medical director of communicable diseases.

The parasite is cryptosporidium, which was detected for the first time in six years in a water sample drawn from the city-owned reservoir in the Bull Run Watershed on Jan. 2. It has been found 13 times since then, most recently in a sample drawn March 12.

After the sixth positive finding, the Portland Water Bureau took the reservoir offline and switched the supply system to the groundwater wells along the Columbia River on Feb. 13. It switched back to the reservoir on March 15, even though seven additional samples taken while it was offline tested positive.

Crypto — as it is commonly called — 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 Milwaukie, Wisconsin. That outbreak prompted the EPA to adopt a rule requiring all municipal water systems to treat for crypto. Portland was granted a variance enforced by the Oregon Health Authority because Bull Run water historically has been so clean. It requires the testing that resulted in the crypto detections this year.

Before the variance was issued in March 2012, crypto had only been detected twice in the reservoir — once in August 2002 and once in December 2011.

Although the state health authority has the primary responsibility for enforcing the rule, the federal Environmental Protection Agency is actively monitoring the situation.

"The number and frequency of cryptosporidium detections since the beginning of the year raise questions about whether (the Portland Water Bureau) can satisfy the conditions necessary to maintain its variance from treatment requirements," says EPA Region 10 Public Affairs Director Marianne Holsman.

Cieslak says there are several reasons why no one should be alarmed if crypto continues to be found in the Bull Run reservoir, however. For starters, the strains detected there are not known to harm people.

"The most dangerous ones are transmitted by cattle and people, and they are banned from the watershed," Cieslak says.

In addition, the amount detected, so far, is still very low. The variance states that the health authority shall revoke the variance if, at the end of a monitoring year, the average crypto concentration is greater than 0.075 oocsysts per 1,000 liters. An oocyst is a microscopic structure found in feces. With more than nine months of testing remaining, the amount detected up until now is well below that level.

Dr. Paul Lewis, the tricounty health officer, agrees, noting there has been no increase in reported cases of cryptosporidiosis since the beginning of the year.

"The longer we go without an increase, the more confident we can become that the water does not pose a threat to the general public," Lewis says.

At the same time, Kari Salis, the health authority's technical manager of drinking water services, can't say there is no risk at all. The standard in the variance is not set or accepted by the EPA or the Centers for Disease Control as an absolutely safe level. Even a minuscule exposure to the right strain could potentially harm someone with a very compromised immune system, such as a late-stage AIDS victim.

"A human could get sick from one organism if it is ingested the right way," Salis says.

Because of that, Cieslak and Salis say the health authority is reviewing options if more and more positive results are found as the test year continues. Although they will not disclose details, both say the agency could act sooner rather than later, depending on the circumstances.

Canceling the variance could cost the Portland Water Bureau a lot of money. In 2009, it estimated that a treatment plant that used ultraviolet light would cost $100 million. A filtration plant that could treat additional contaminants was estimated at $385 million. Water rates might have to be raised to pay for either option.

The Oregon Citizens Utility Board, which advises the City Council on rate-related issues, is aware of the situation but unwilling to second-guess the Water Bureau on water quality and public health matters.

"The process the Water Bureau should use to make treatment decisions is to continue their ongoing consultation with those public health and water quality experts and regulators," says Citizens Utility Board liaison Janice Thompson.

The bureau not only provides water to city residents and businesses, but to 19 wholesale customers in the region. Some rely entirely on Portland for water, while others mix it with water from other sources, including rivers and wells. They have five-, 10- and 20-year contracts with the bureau.

One is the Tualatin Valley Water District, which currently buys some of its water from the city. General Manager Mark Knudson says the district board is concerned about the repeated crypto findings and wondering what Portland is going to do if they continue. At the same time, the district is planning to replace the water from the city with treated water from the Willamette River in a few years. It does not want to help Portland build a treatment plant that might not be completed before the switch.

You can find the ongoing test results at

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