By Peak Johnson

Last Monday, Portland’s water bureau located the cryptosporidium parasite in a test of drinking water from the Bull Run watershed. After not finding any traces of the parasite for four years during weekly water samplings, Portland has now detected trace signs of the parasite eight times this year.

"This is the most cryptosporidium we've detected in more than a decade," Yone Akagi, the bureau's water quality manager, told The Oregonian.

This outcome, according to The Oregonian , has led the city to consider building an expensive treatment plant. Officials have said that there is no reason for alarm and that the water bureau "does not believe there is any increased public health risk" but suggests that people with weak immune systems consult their doctors about drinking water, according to a press release.

Portland's water bureau does not treat its water for cryptosporidium, a parasite found in animal and human waste.

The bureau received an exemption in 2012 from the Oregon Health Authority to forgo treating for the pathogen after the water bureau found no cryptosporidium from 2002 and 2012. Portland opted instead to monitor for the microorganism through regular testing.

Akagi added that “humans are barred from the Bull Run Watershed, making animal scat the most likely source of the parasite.”

If the water bureau locates “more than one oocysts — a hard structure found in feces but too small to see — per 13,300 liters of water in one year,” then the state could revoke Portland’s exemption.

According to The Oregonian, the outbreak of cryptosporidiosis “could force the bureau to build an ultraviolet treatment plant, expected to cost at least $89 million, according to water bureau planning documents.” The city could also build a filtration treatment system that would filter out sediment in addition to microorganisms, but that could cost around $300 million.

Whether or not the bureau will have to build the treatment depends on what future tests reveal.

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