Maine Public staff

Willis Ryder Arnold / Maine Public

Portland’s East End beach and trail closed Thursday after about a million gallons of partially treated sewage spilled out of a Maine wastewater treatment plant and into Casco bay.

Scott Firman with the Portland Water District says the sewage overflowed when valves that should have been reopened after maintanence were inadvertently left closed.

"When the flows picked up this morning because of the rain, the water had nowhere to go because of those two valves, and that's what resulted in that observed overflow," Firman says.

Firman says the wastewater was far enough along in the treatment process that it was about a half hour from being released into the bay. However, there are still concerns about possible elevated levels of bacteria. The Maine Department of Environmental Protection issued a statement that said staff from the Health Beaches Program took water samples Thursday morning, which are currently being analyzed.

A spokesperson told the AP that it was the first time the plant had experienced an overflow of this kind. In a Facebook post, the Portland Parks, Recreation and Facilities Department called it "a complete washout."