The city of Portland's Bureau of Environmental Services warned residents today that sewage may have leaked into the Willamette River during the ice storm that caused widespread power outages.

BES has 99 pumping stations that in normal times send sewage to the Columbia Boulevard Wastewater Treatment Plant. But due to a loss of electricity as trees crashed into power lines across the city, at least four of those pumping stations went offline.

In past decades, the city commonly allowed sewage to flow into the Willamette after heavy rains, but the "Big Pipe Project," completed in 2011, saw the expenditure of $1.4 billion to eliminate 94% of the spills into the river and 99% of the spills into the Columbia Slough. That infrastructure, however, is still dependent on electricity, and until bureau staff can get to the pumping stations, it will be unclear whether sewage flowed to the river.

"Environmental Services is unable to confirm if sewage is being released from these pump stations to the Willamette River," BES said in a statement. "Out of an abundance of caution, the public is advised to avoid the river for the next 48 hours in case a sewage release is occurring."