Like many harbors near cities along the eastern seaboard, the Boston Harbor in Massachusetts has been used for centuries as a receptacle for raw and partially treated sewage from the city of Boston and surrounding towns. In the late 1800s, Boston designed a sewage and stormwater collection system. This sewage system combined millions of gallons of untreated sewage from homes, schools, hospitals, factories, and other buildings with stormwater collected from streets during periods of moderate to heavy rainfall. The combined sewage and stormwater collected in the sewage system was discharged untreated to Boston Harbor on outgoing tides. Sewage from communities surrounding Boston was also piped to Boston's collection system and discharged to Boston Harbor and the major rivers leading to it: the Charles, Mystic, and Neponset Rivers. Many of the sewage pipes, tunnels, and other infrastructure built in the late 1800s and...