When the EPA took charge of efforts to cleanup the Charles in 1995, the situation was dire. They issued the river a D grade, declaring it safe to swim in a mere 19% of the time. Much has changed since then. Through the coordinated efforts of government agencies and non-profit organizations like the Charles River Watershed Association, the Charles has undergone an improbable transformation. In 2004, the river received a B+ rating and has stayed in that range ever since. Though its reputation remains—it’s tempting to blame the Standells, who immortalized the river in a not-so-positive light with their 1966 hit “Dirty Water”—the Charles is actually one of the cleanest urban rivers in the United States these days. Last summer the river had its first officially sanctioned public swim in over 50 years.
So what’s keeping the Charles from breaking into A territory? Sewage, among other things. In a sense, the Charles River may be the oldest sewer system in the United States. In the early days of Boston, the Charles flowed freely into the ocean. Residents took advantage of this by dumping waste directly into the river, where it ultimately washed out to sea.
This tradition continued well into the 20th century even after dams restricted the river’s flow. Many sewage lines were routed directly to the stormwater drains that empty into the Charles, a system known as combined sewer overflows (CSOs). Although this practice is now illegal, many of old lines remain, and being underground they are difficult to detect and locate, and costly to replace. Totally eliminating CSOs is well beyond the resources of the Massachusetts Water Resource Authority, so a certain amount of raw sewage is likely to be a feature of the Charles for the foreseeable future.
The Massachusetts Oyster Project is one of the more unique projects aimed at mitigating this problem. Once abundant in Boston Harbor and the Charles, oysters are adept aquatic filters. The thought is that by reestablishing self-sustaining oyster beds at strategic points along the river bed, a good chunk of the pollution from raw sewage and other sources could be captured and neutralized. The project’s founders estimate that it would take roughly 225 square feet of oyster beds to do the trick. Presumably, they wouldn’t be harvested for human consumption afterwards.