Parasites Force Portland To Switch Water Supply

Portland is no longer using water from the Bull Run reservoir. The decision to switch to groundwater from the Columbia South Shore Well Field was made after the parasite, cryptosporidium, was found for a fifth time this season.

The city said that levels of cryptosporidium were low and that switching water sources was not required.

"The recent detections do not pose an increased health risk," said Water Bureau Administrator Michael Stuhr. "After a series of very low level detections, we are proactively activating our secondary source while we collect more data.

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"The City continues to be in compliance with the treatment variance issued by the Oregon Health Authority."

In addition to providing water to the people of Portland, Bull Run supplies several other areas including Gresham and Sandy.

The discovery over the weekend follows nearly five years of the bureau finding no trace of the parasite, cryptosporidium.

Last week, the water bureau said they do "not believe there is any increased public health risk" but suggested that people with severely weakened immune systems consult with their health care provider about drinking the water.

While many cities treat their water for cryptosporidium, Portland received an exemption from the Oregon Health Authority in 2012. The city had gone ten straight years of not finding any trace of the parasite.

Instead of treating the water, the city normally conducts testing twice a week,

Before bringing Bull Run back online, the city might consider other long-term options including a water treatment plant and a filtration system.

The city says that the Columbia South Shore Well Field is a high-quality water supply which meets or surpasses all federal and state drinking water regulations.

It may take up to two weeks, depending on location, for groundwater to make its way through the distribution system to homes and businesses. The well field is used as a secondary source for the Bull Run Watershed, most often in the summer when the region's demand increases.

The city's water bureau says that they will 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.

Public notification is not required, the city says. They says that they inform the media and sensitive water users, as a practice, when it activates groundwater and when it has significant operational changes.

The bureau will continue to provide public notice as decisions are made.

Photo Portland Water Bureau