Dorchester Bay is bordered roughly by Columbia Point in Dorchester to the north, Savin Hill and Commercial Point in Dorchester to the west, and Quincy’s Squantum Point and Moon Head to the south. Lying in the middle of Dorchester Bay is Boston’s Thompson Island.

The project consists of a channel extending southwesterly from the main ship channel in Boston Harbor, through Dorchester Bay, and up the Neponset River to the Neponset Highway Bridge (Route 3) in Dorchester. The channel is 18 feet deep and 175 feet wide from the main ship channel to Commercial Point (the channel runs between Columbia Point and Thompson Island). From Commercial Point to the Neponset Highway Bridge, the channel is 15 feet deep and 100 feet wide.

The channel was constructed on the condition that the Commonwealth of Massachusetts dredge and maintain the two-mile portion of the river between the Neponset Highway Bridge and Milton Mills to a depth of six feet at varying channel widths. The state dredged the channel in 1910 and has periodically maintained it.