Bainbridge Island officials reported a major sewer spill in Eagle Harbor Saturday as a result of a break in the Highway 305 south sewer force main.

Public beaches have been closed to wading, swimming or shellfish harvesting as a precautionary measure, city officials said.

The break occurred near 1220 Donald Place, officials said. Sewer plant staff received an alert early Saturday morning for an unrelated incident and noticed remarkably low flows at the plant.

Public works employees investigated and found that sewage was not reaching the plant, indicating a likely force main break. Crews confirmed the force main break around 3:30 p.m. Aug. 31.

City personnel planned to fix the line late Saturday at around 9:30 p.m., during low tide.

Bainbridge officials did not have an estimate of the volume of sewage spilled into Eagle Harbor.

The break occurred in a 40-year-old cast iron pipe. City officials said the pipe had a previous break and the city has a replacement project under design for construction in 2014.