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The City of Portland, Oregon

Portland Water Bureau

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Cryptosporidium Detected In Bull Run Drinking Water; Monitoring Continues

Quote - Dr. Paul LewisThe Portland Water Bureau received results today from a water sample collected on Sept. 24 that was positive for Cryptosporidium, a potentially disease-causing microorganism. The sample had one oocyst ofCryptosporidium detected in a 10-liter sample.

At this time, the bureau and public health partners at Multnomah County continue to believe Bull Run water is safe to drink.

To reduce the risk of the public’s exposure to Cryptosporidium, the bureau continues to monitor forCryptosporidium, protect the watershed, notify the public, and work with its health partners to make the best decisions for public health.


The Portland Water Bureau has monitored for Cryptosporidium under conditions of a variance for the treatment ofCryptosporidium issued by its regulators at the Oregon Health Authority (OHA). As a result of the detections earlier this year, the Oregon Health Authority informed the Portland Water Bureau that the variance from treating for Cryptosporidium 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 Cryptosporidium 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.

Learn more about the Cryptosporidium detections earlier this year. You can also view all sampling results posted to the City’s website at

As always, the bureau recommends that people with severely weakened immune systems seek specific advice from their health care providers about drinking water. There is no need for the general public to take additional precautions.

Bull Run Water Remains Safe to Drink

Current evidence from public health data, monitoring results, and watershed investigations, as well as extensive consultation with public health officials, have provided confidence in the continued safety of the Bull Run water.

“We continually monitor for human illness caused by Cryptosporidium but since past detections of Cryptosporidium oocysts in Bull Run water have not been associated with an increase in human disease, I do not expect it to be different this time,” said Multnomah County Health Officer Dr. Paul Lewis.

Next Steps

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

You can refer to Frequently Asked Questions to find answers to questions about Cryptosporidium and treatment.