Halfway into 10-year timeline for Bull Run filtration, Portland is still monitoring water

By Alex Hasenstab (OPB)
Jan. 4, 2023 8:23 p.m.

Halfway into its timeline to create a new filtration system for the Bull Run Watershed, the Portland Water Bureau continues to monitor the water, specifically for an organism called cryptosporidium.

The city of Portland has two drinking water reservoirs in the Bull Run watershed.

The city of Portland has two drinking water reservoirs in the Bull Run watershed.

Cassandra Profita / OPB/EarthFix


Jodie Inman, chief engineer with the bureau, said while the Bull Run Watershed has supplied clean water for decades, in 2017 they temporarily halted use of that water out of an abundance of caution, when cryptosporidium was detected.

The small parasite can cause cryptosporidiosis, a serious illness. Symptoms can include diarrhea, vomiting, fever and stomach pain. According to the Centers for Disease Control and Prevention, people with healthy immune systems recover without medical treatment, but people with severely weakened immune systems could get serious or life-threatening illness.

In 2017, The Oregon Health Authority ordered the city of Portland to treat its water for cryptosporidium, by building a new filtration system by 2027


“What the filtration system will do, is it will actually group together what particles we do have in our water, including those disease-causing organisms called cryptosporidium,” Inman said. “And then it will filter them out of our system. And then we’re going to treat it with disinfectant and then serve it to the town.”

The filtration system is expected to cost around $1 billion. It’s currently still in the design phase. In addition to essentially eliminating the risk of cryptosporidium, the filtration system could keep the water free from debris and smoke particles in the case of a wildfire.

Levels of cryptosporidium have been low in the watershed, low enough that the city has continued using it as its main water source.

The Environmental Protection Agency has estimated that a small percentage of the population could experience gastro-intestinal illness from the levels of cryptosporidium in Bull Run, and advises that customers who are immunocompromised should consult with a health care professional about the safety of drinking the tap water.

The bureau is required to release weekly water testing results for the public. Levels of cryptosporidium increase in the winter, but levels remain low enough that customers do not need to take any extra precautions.

“One of the things that tends to happen in the winter is you get more storms and rain, which flush more things down into our reservoirs,” Inman said.

The Bull Run Watershed provides all or part of the drinking water for the Portland Water Bureau and the Burlington, City of Gresham, City of Sandy, City of Tualatin, Green Valley, GNR, Hideaway Hills, Lake Grove, Lorna Domestic Water, Lusted, Palatine Hill, Pleasant Home, Raleigh, Rockwood, Skyview Acres, Tualatin Valley, Two Rivers, Valley View and West Slope water districts.