This move comes after low levels of the parasite cryptosporidium were detected in the Bull Run Watershed.
Officials said the switch to groundwater was not required and was instead done out of an “abundance of caution.”
“The recent detections do not pose an increased health risk. After a series of very low level detections, we are proactively activating our secondary source while we collect more data,” said Water Bureau Administrator Michael Stuhr. “The city continues to be in compliance with the treatment variance issued by the Oregon Health Authority.”
The Columbia South Shore Well Field meets or surpasses all federal and state drinking water regulations, according to the Portland Water Bureau. It’s often used as a secondary water source for the Bull Run Watershed in the summer when the area’s water demand increases.
Officials will continue to sample the Bull Run Watershed for cryptosporidium, and after consulting with public health officials, will decide when to switch water supply back to it.
“Portland is fortunate to have access to the two largest supplies of drinking water in Oregon, which allow the bureau to be prepared to meet the range of conditions that occur in the Portland water system,” the Portland Water Bureau said.
Anyone with questions can call the water line at 503.823.7525.