The Maiden River, a small tributary of the Mystic River, flows southerly from Malden Square and forms a partial boundary between Medford and Everett. The river was once used for the shipment of coal and other barge traffic prior to construction of the Metropolitan District Commission dam and locks located immediately downstream, at the confluence of the Mystic and Malden rivers. The Malden River is now chiefly used by a small recreational fleet.
The project consists of a 1.5-mile-long channel extending from the junction of the Malden and Mystic rivers to the Medford Street Bridge. Completed in 1921, the channel is six feet deep and 100-150 feet wide.