Sewage flowed through some Portland streets after pressure from heavy rains dislodged at least one manhole cover and caused a landslide that broke a sewer pipe on Monday.

An open manhole along Northwest 13th Avenue between Quimby Street and Raleigh Street in the Pearl District sent brown water gushing onto the pavement and forced streets to close until 10 p.m. Monday, said John Brady, a Portland Bureau of Transportation spokesman. Crews have since replaced the manhole cover, and the high water has mostly receded into small pools. 

Workers replaced other manhole covers that came loose in the city, but Brady said he didn’t know how many or where. 

“There was a lot of water in a little amount of time and that just overtaxed the system,” he said. 

In Southwest Portland, a landslide broke a pipe Monday along Southwest Montgomery Drive east of Vista Avenue and led to sewage flowing downhill on at least four streets for several hours. The rate was about 10 to 15 gallons a minute.

The city’s sewer system carries sewage and stormwater runoff in the same pipes. The discharge is typically 20 percent sewage, said Linc Mann, a Portland Bureau of Environmental Services spokesman. It’s possible that there’s at least some risk of E. coli in the water, but the contamination would be very diluted, he said.

Heavy rain also caused the sewer system to overflow into the Willamette River and the Columbia Slough on Monday. People should avoid high rainwater if they can and clean themselves thoroughly if they come into contact with the water, Mann said.

“All flood water is filthy,” Mann said. “It flows across streets and picks up debris and dog waste and anything else there. Water from the sewer only adds to the problem.”

Monday was the third case of sewage overflowing into the Willamette since November and could last three days, Mann said. The city has had no more than four sewage overflows between November and April — which the bureau considers the winter season — since November 2011.

The city won’t be able to calculate how much sewage overflowed into the river this time until after the spill ends, he said.

Torrential downpours continue to hit Portland and the Willamette Valley, with more rain on the forecast for Tuesday evening into Wednesday. Flood warnings have been issued for much of the region through Thursday.

— Everton Bailey Jr.
503-221-8343; @EvertonBailey

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