PITTSFIELD — An overflowing tank at the city wastewater treatment plant off Holmes Road spilled sludge into the Housatonic River early Tuesday morning.
City leaders believe 1,200 gallons of wastewater left the facility— 500 gallons of which likely reached the river.
Ricardo Morales, the city’s commissioner of public services and utilities, said there is no risk to the city’s drinking water supply from the spill. Aquatic life downstream from around 901 Holmes Road may be impacted over the next 48 hours by depleted oxygen levels that could result from the sludge, he said.
The spill began at about 5:30 a.m. and continued until about 6:45 a.m. City officials followed new state reporting protocols for “sewage pollution” and sent out a CodeRED alert and press release to local media.
New state rules require that municipalities alert the public and state when untreated or partially treated wastewater discharges into public waterways. The rule went into effect this year. Morales said the types of events that qualify for notice are fairly common.
The state tracks these events in a database that as of Tuesday had more than 500 entries since June, two of which occurred Monday in New Bedford and Fall River.
The city’s alert cautioned people to “avoid contact with these water bodies for 48 hours after the discharge or overflow ceases due to increased health risks from bacteria and other pollutants.”
Morales said the leak occurred in one of the safer points in the treatment process. What spilled was “biologically digested sludge.”
When sewage comes into the treatment plant from the city it’s treated and then denser materials are separated from the liquid material. That denser material is “dewatered further,” Morales said, and the resulting material is mixed with new water and bacteria to “further clean it.”
This cleaning happens in blend tanks. One of the blend tanks at the facility overflowed with the treated sludge. Morales said the city is investigating whether the overflow was the result of a computer system or mechanical failure of the pumps attached to the tank, human error or a combination of all three.
“If it had happened in a different part of the system — like raw sewage coming in the plant and it overflowed — that is a much more dire situation for the wildlife in the river,” Morales said. “Outside of the clean water that comes out at the end of the entire system, this is like the best condition of an overflow for the wildlife that could have happened.”
The commissioner said he estimated the sludge would have dissipated by the time it reaches where the Housatonic River nears New Lenox Road, about a mile downriver from the spill.