A sewage treatment plant in North Andover, Massachusetts, spilled 8 million gallons of waste into the Merrimack River Monday after power went out during a heavy storm.
For 13 hours, power was out at the Greater Lawrence Sanitary District.
According to Newburyport Mayor Donna Holaday, in that time, the sewage overflowed into the Merrimack River in what the Environmental Protection Agency calls an "unexpected release."
The EPA and the Massachusetts Department of Environmental Protection are investigating.
"This is a major health threat that needs to be looked into, but we need to look at the causes," said Rusty Russell, executive director of the Merrimack River Watershed Council.
Exposure to sewage can cause diarrhea, vomiting and stomach pain, according to the Centers for Disease Control and Prevention.
There is no drinking water intakes from the river below the area of the spill. Therefore, no impacts to drinking water are expected.
In a letter written by the Sanitary District's Executive Director Cheri Cousins to its board of commissioners, Cousins said they lost power early Monday morning as a result of a wind and rain storm.
The facility gets their power from two separate power sources, so they have backup power if one source goes down. In this case, both were out.
"I think every sanitary district in the country should have a backup generator," Haverhill Mayor James Fiorentini said. "There's always going to be power outages. One-hundred-year storms seem to happen every two-three years now and that's what happens."
An on-site generator started automatically at the Treatment Facility, according to Cousins, but only gave a "preliminary treatment" to the sewage before it went into the river.
The facility is set to add two generators in the next year that would eliminate its need for power from the grid.
Russell said the river will naturally wash the sewage out to the ocean, but it could take days.
"The standard learning is it that it takes up to 72 hours," said Russell. "It can happen faster in a fast moving river, but this river has a lot of territory to cover."