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The City of Portland, Oregon

Portland Water Bureau

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Information on Cryptosporidium

Bull Run LakeWe're moving! Find our updated Cryptosporidium information on our new website.


Drinking water treatment for Cryptosporidium, a potentially disease-causing microorganism, is regulated by the Long-Term 2 Enhanced Surface Water Treatment Rule (LT2). This rule requires systems that use an unfiltered surface water source, such as the Portland Water Bureau’s Bull Run, to treat for Cryptosporidium. LT2 also contained requirements for all systems to cover, treat or replace uncovered finished drinking water reservoirs to address possible contamination from Cryptosporidium, Giardia, and viruses.

In March 2012, based on the results of a year-long intensive sampling for Cryptosporidium and the limited sources and low occurrence of Cryptosporidium in the Bull Run Watershed, the Oregon Health Authority (OHA) issued the Portland Water Bureau a variance from the requirements to treat for Cryptosporidium.

In May 2017, the Portland Water Bureau was informed by OHA that the variance was being revoked as a result of a series of low-level detections of Cryptosporidium in January through March of 2017. The number of Cryptosporidium oocysts detected showed that the Portland Water Bureau was no longer able to demonstrate an equivalent level of Cryptosporidium from untreated Bull Run water that would be expected with treatment.

As a result, the Portland Water does not currently treat for Cryptosporidium, but is required to do so under the drinking water regulations. Portland is working to install filtration by 2027 under a compliance schedule with Oregon Health Authority. In the meantime, Portland Water Bureau is implementing interim measures such as watershed protection and additional monitoring to protect public health. Consultation with public health officials has concluded that at this time, customers do not need to take any additional precautions.

Exposure to Cryptosporidium can cause cryptosporidiosis, a serious illness. Symptoms can include diarrhea, vomiting, fever, and stomach pain. People with healthy immune systems recover without medical treatment. According to the Centers for Disease Control and Prevention (CDC), people with severely weakened immune systems are at risk for more serious disease. Symptoms may be more severe and could lead to serious life-threatening illness. Examples of people with weakened immune systems include those with AIDS, those with inherited diseases that affect the immune system, and cancer and transplant patients who are taking certain immunosuppressive drugs.

The Environmental Protection Agency has estimated that a small percentage of the population could experience gastrointestinal illness from Cryptosporidium and advises that customers who are immunocompromised and receive their drinking water from the Bull Run Watershed consult with their health care professional about the safety of drinking the tap water. The Portland Water Bureau and Burlington, City of Gresham, City of Sandy, City of Tualatin, Green Valley, GNR, Hideaway Hills, Lake Grove, Lorna Portland Water, Lusted, Palatine Hill, Pleasant Home, Raleigh, Rockwood, Skyview Acres, Tualatin Valley, Two Rivers, Valley View and West Slope Water Districts receive all or part of their drinking water supply from Bull Run. To learn if your drinking water comes from Bull Run, please contact your local drinking water provider.


Treatment Variance for Cryptosporidium

Portland developed a comprehensive treatment variance request based on the results of a year-long water quality sampling and study of Bull Run water.

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