Groton - The town Public Works Department said Thursday that thousands of small, plastic items escaped from a sewage-treatment facility during flooding last week and have washed up on beaches from Eastern Point through Mumford Cove and Groton Long Point.

"We thought everything was kept in the plant, and it's all over the plant, in other tanks and pipes and on-site," Gary Schneider, head of Groton's Department of Public Works. "But it got loose, probably because of the volume of rain we had. It got into the wet wells, which we pump out of, and got into the Thames River and Fort Hill brook, which feeds into Mumford Cove and Long Island Sound."

The black pieces, which are about one inch in diameter, do not pose an environmental or health threat and can be treated as regular beach litter, being thrown away with other trash, Schneider said. The items were used inside Groton's wastewater-treatment plant on Gary Court, providing the microscopic organisms that clean sewer water with more surface area to live.

"The bugs can live on these things, so there's more treatment in less space," Schneider said.

The plastic pieces are typically held in the plant by screens, but the heavy rains last week forced an enormous amount of water through the facility - about 10 million gallons each day. The screen was knocked out of place by the resultant flooding, setting the plastic pieces free.

Residents who encounter the black pieces can call Public Works at (860) 446-4083, where staff will direct workers to clean up the site, Schneider said. Groton officials informed the state Department of Environmental Protection and the Coast Guard of the incident.

m.collette@theday.com