The Historic River Town of Philadelphia — And the Urgent Need for Swimmable Waters

Jerry Kauffman, University of Delaware 
Lucia Osborne, American Littoral Society
Andy Kricun, Environmental Consultant

As Philadelphia celebrates America's 250th birthday in the midst of a blistering 100‑degree heat wave, it is worth remembering that this city is one of the world’s great historic river towns. The Delaware and Schuylkill Rivers—and the creeks that feed them—have shaped Philadelphia’s identity for millennia. Today, they remain a billion‑dollar natural asset, offering recreation, cooling, ecological richness, and drinking water to millions. Yet these waters are still burdened by one of the most persistent and solvable pollution challenges of the 21st century: raw sewage discharges, known as combined sewer overflows (CSOs), contaminating our waterways as many as 195 days out of the year. If Philadelphia is to honor its river heritage and protect its residents during increasingly dangerous heat waves, it must commit to making its rivers and creeks truly clean. ​

Long before William Penn arrived in 1682, the Lenape called the Delaware River Lenape‑hoking and treated its valley as a shared life source to be protected for future generations. Penn himself marveled at the abundance of oysters and sturgeon, and by the mid‑18th century Benjamin Franklin was petitioning the Pennsylvania Assembly to curb pollution from tanneries and slaughterhouses fouling the river. Franklin later helped form one of the first city committees to study water pollution, and in 1790 he willed funds to improve Philadelphia’s drinking water system after epidemics linked to contaminated water. By 1801, Philadelphia had established the nation’s first municipal water system, and by the 1850s it preserved Fairmount Park—still one of the largest urban park systems in the country—to safeguard its watershed.

This legacy underscores a simple truth: Philadelphia has always been a river city, and its rivers have always been central to public health, prosperity, and civic identity.

Today, as temperatures soar, many Philadelphians won’t be able to escape to the beaches of the Jersey Shore or the lakes of the Poconos, nor will they have access to many of the City’s pay-to-play pools. Instead, they’ll seek relief along more than 80 miles of waterways: the Delaware, the Schuylkill, and the Poquessing, Pennypack, Frankford/Tacony, Wissahickon, and Darby/Cobbs creeks. These waterways are an oasis in extreme heat, a refuge for residents, and a vital part of the city’s climate resilience.

But these waters are not as clean or safe as they should be. The city’s 19th‑century engineers designed a single combined sewer system that carries both stormwater and sewage in the same pipes. At the time, this was a major improvement from open sewage trenches in the streets, and they could not foresee the population growth, urbanization, and climate‑driven rainfall that would overwhelm the system. Today, when heavy rain hits, the pipes overflow—sending untreated sewage into rivers and creeks. These CSOs cause bacteria levels to spike far above safe swimming thresholds, making the water unsafe for recreation, paddling, fishing, and cooling off. In most cases, it takes three days for the bacteria to return to normal levels. In addition, this same CSO overflow events often result in raw sewage backing up into basements of Philadelphians.

And here is the most striking—and troubling—fact: many of Philadelphia’s smaller creeks are already designated for swimming under Pennsylvania’s water quality standards. Legally, they are supposed to meet “primary contact recreation” criteria. In practice, they routinely fail. Monitoring shows that after storms, bacteria levels in creeks like Cobbs, Tacony, and Pennypack soar well above safe limits. The law says these waters should be swimmable; the City’s inadequate infrastructure ensures they are not.

This gap between legal designation and lived reality is unacceptable—especially for communities that rely on local creeks for recreation and relief from extreme heat. Clean water access is not just an environmental priority; it is a public health necessity.

The remedies are well known. Other historic U.S. cities—Boston, Baltimore, Chicago—have invested heavily in CSO control, modernizing sewer systems and reducing bacteria pollution to meet federal and state standards. Philadelphia must follow suit. Our research estimates that fixing the CSO problem would cost hundreds of millions of dollars, funded through a combination of federal, state, and local sources. Spread across years and across the city’s population, the investment is affordable—and the benefits are enormous. Swimmable water quality would generate billions of dollars in economic, recreational, ecological, and public health value, exceeding costs by at least five to one. Chicago’s reversal and cleanup of its river system shows what is possible: today, people swim in a river once considered hopelessly polluted.

Philadelphia has made progress before. The 1948 Schuylkill cleanup ordered by President Truman, the 1961 Delaware River Basin Compact signed by President Kennedy and four governors, and the 1972 and 1977 Clean Water Act amendments all transformed the region’s waters. As a result, American shad now swim past the Ben Franklin Bridge and spawn hundreds of miles upstream. The next step is clear: invest in CSO abatement to meet the Clean Water Act’s fishable and swimmable goals and protect the public health of our residents.

​Philadelphia is a world‑class city built between two beautiful rivers. We see this in the crowds on the Art Museum steps during the World Cup, in the rebirth of Penn’s Landing, in the Delaware River Trail stretching to the Tacony‑Palmyra Bridge, and in the Schuylkill River Trail reaching Bartram’s Garden. As we experience more extreme heat, the rivers are central to the city’s future. ​