For most of the Charles River’s civic his­tory, bath­houses and beaches crowded its shores. Places like Mag­a­zine Beach in Cam­bridge, Mass., and the Esplanade in Boston offered recre­ation and relief for swim­mers on the hottest days of the year. But in the mid-​​1950s all of that changed. Due in part to an anti­quated runoff system that inte­grated both stormwater and raw san­i­tary sewage, the river had become too pol­luted for swimming.

Swim­mers at Charles Bank beach circa 1940. Photo Cour­tesy of the Boston Public Library, Leslie Jones Collection.

Swim­mers at Charles Bank beach circa 1940. Photo Cour­tesy of the Boston Public Library, Leslie Jones Col­lec­tion.

Efforts to clean up the river com­menced in the 1960s, but only recently have those efforts begun to pay off. According to research by civil and envi­ron­mental engi­neering asso­ciate pro­fessor Ferdi Hell­weger, the river is now swim­mable 70 per­cent of the time. The chal­lenge is knowing which 70 per­cent, said Hell­weger, whose team is devel­oping a com­pu­ta­tional model to fore­cast river water quality.

Such a system would be indis­pens­able if the Charles River Con­ser­vancy gets its way: The envi­ron­mental advo­cacy group hopes to soon restore reg­ular swim­ming to the river. On Sat­urday, Hell­weger par­tic­i­pated in a his­toric step toward real­izing that goal when he joined nearly 150 local res­i­dents, young and old, to plunge in the river’s waters for the first com­mu­nity swim in more than half a century.

Like many of the par­tic­i­pants, Hell­weger was pleas­antly sur­prised by the expe­ri­ence: “It was won­der­fully refreshing, sur­pris­ingly so. When you are on the Esplanade in a heat wave, you don’t realize relief is just a few feet away,” he said.

The event marked the first in a multi-​​year roll-​​out plan that will even­tu­ally pro­vide reg­ular access at mul­tiple sites throughout the summer, said Hell­weger, who has part­nered with the CRC on a number of water-​​quality research investigations.

Civil and envi­ron­mental engi­neering asso­ciate pro­fessor Ferdi Hell­weger was one of more than 100 people to brave the waters of Charles River on Sat­urday in the first com­mu­nity swim in more than 50 years. Photo by Topher Baldwin/​Charles River Conservancy.

Per­haps the biggest chal­lenge to making the Charles a recre­ational hotspot is res­i­dents’ per­cep­tions. Boston’s unof­fi­cial theme song—“Dirty Water” by the Standells—sums it up. “It doesn’t even occur to people to swim in it,” said Hell­weger. “It’s been more than 50 years.”

But with public aware­ness events like this weekend’s, Hell­weger and the CRC hope that will even­tu­ally shift. In 2006 the Stony Brook Sewer Sep­a­ra­tion project mod­ern­ized a vast por­tion of the water run-​​off system.

Since then the sur­rounding com­mu­ni­ties have per­sis­tently worked to iden­tify illegal san­i­tary dis­charges into the storm sewer system, including one that Hellweger’s team helped dis­cover. A whole apart­ment building was dis­charging its san­i­tary sewage into the storm sewer, from where it entered the Muddy River, and then onto the Charles. Together, these efforts have cut pol­lu­tion by 99 per­cent, said Hellweger.

Despite these improve­ments, public per­cep­tion remains dour, unsur­pris­ingly given the river’s cul­tural posi­tion in the city.  “But once you realize it’s amaz­ingly pleasant, people value it as a resource,” said Hell­weger. He plans to swim again next year and every year after that.