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The City of Portland, Oregon

Portland Water Bureau

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Cryptosporidium Detected in Bull Run Drinking Water

The Portland Water Bureau received results today from a sample collected on Sept. 27 that was positive for Cryptosporidium, a potentially disease-causing microorganism. The detection was from a sample collected from the Bull Run Watershed intake as part of ongoing monitoring for Cryptosporidium. One Cryptosporidium oocyst was detected in the 10-liter sample. This detection follows a detection of a single oocyst from a 10-liter sample collected on Sunday, Sept 24. Eighteen other 10-liter samples collected between Sept 24 and Sept. 27 were all negative for Cryptosporidium

 “Even from a highly protected watershed such as the Bull Run, it is not unusual to detect low levels of Cryptosporidium from wildlife sources. We continuously monitor the rate of human illness caused by Cryptosporidium and will know if there is an increase” said Multnomah County Health Officer Dr. Paul Lewis. “Fortunately, there has never been a documented outbreak of Cryptosporidium linked to Bull Run water.”

Cryptosporidium detections at these low levels are not expected to result in an impact to public health. Public health surveillance during and after a series of low-level detections from January through March of this year did not see an increase in Cryptosporidium related disease. While the general public is not being advised to take additional precautions, as always, the bureau recommends that people with severely weakened immune systems seek specific advice from their health care providers about drinking water.

“Together with our public health partners at Multnomah County, we continue to believe Bull Run water is safe to drink,” said Portland Water Bureau Administrator Michael Stuhr. “We will continue monitoring our water and working with our health partners to make the best decisions for public health in our community.”

Portland Water Bureau has been monitoring for Cryptosporidium under conditions of a variance for the treatment of Cryptosporidium issued by its regulators at the Oregon Health Authority. As a result of the detections earlier this year, the Oregon Health Authority (OHA) informed the Portland Water Bureau that the variance would be revoked no later than Nov. 22, 2017. On Aug. 2, City Council directed the bureau to construct a water filtration plant to meet the treatment requirements. The Portland Water Bureau will submit a schedule for construction of a filtration plant and ongoing measures to continue to protect public health to OHA by Oct. 11.

The bureau will continue to sample the Bull Run for Cryptosporidium; gather information about these detections; and notify the public, its regulators and health officials of any additional detections.

The public and the media are encouraged to view all sampling results posted to the City’s website at

Customers with questions regarding water quality can call the Water Line at  503-823-7525.