The city of Salem is warning people to stay out of the Willamette River downstream of Keizer’s River Road Park following an accidental sewer overflow.

The city operates a wet weather treatment facility at the park.

At 11:30 a.m. Tuesday, crews doing routine maintenance accidentally opened a remotely controlled valve on the emergency bypass gate, city spokesman Mike Gotterba said.

About 4,000 gallons of untreated sewage escaped to the river before crews noticed the open valve at 11:59 a.m.

The city has posted warning signs, which will be removed once bacteria levels return to normal. It also reported the spill to the Oregon Department of Environmental Quality.

The spill is relatively minor compared with the 22 million gallons the city released to the river in November 2016 and 57 million gallons it released in early February 2017 and 1.18 million gallons it released in mid-February 2017., 503-399-6779 or follow at