A potentially deadly parasite was found in a sample of water taken from the Bull Run reservoir on Monday, the same day the Portland Water Bureau took it offline.
Although bureau officials say the level of Cryptosporidium was very low, it is the seventh time that the parasite was found in 29 samples taken from the reservoir this year.
Portland's groundwater wells along the Columbia River are now supplying water to the system that serves residents and businesses in the city, and cities and water districts outside Portland that buy water from the bureau.
"The health and safety of our customers is our top priority" bureau Administrator Michael Stuhr said in a press release announcing the latest finding on Feb. 15. "We will continue to work with our partners at Multnomah County Health Department and Oregon Health Authority while monitoring our drinking water source."
The wells will supply water for the foreseeable future while the bureau continues sampling the reservoir under a variance approved by the Oregon Health Authority. There is no deadline for switching back to Bull Run water.
"Our process for making that decision is to continue to sample the Bull Run for cryptosporidium and gather information about these detections. With additional information, and in consultation with public health officials, the bureau will decide when to re-activate the Bull Run supply," says bureau spokeswoman Jaymee Cuti.
Crypto – as it is commonly called — can cause cryptosporidiosis, a respiratory and gastrointestinal illness. It can affect anyone, but is especially dangerous to immunodeficient people. An outbreak killed 104 people and sickened thousands of others in 1993 in Milwaukie, Wisconsin.
The outbreak prompted the U.S Environmental Protection Agency to adopt a rule requiring cities with open water sources like Portland to treat for crypto. The OHA granted Portland a variance because Bull Water has been so historically clean.
But the variance requires the bureau to monitor for crypto and report it fundings. The OHA has the authority to cancel the variance and order the bureau to build a plant to treat for crypto, which could cost $100 million or more. It would be financed by water customers, inlcuding those outside of Portland.
For a previous story on the issue, visit tinyurl.com/z5ngul6.