Don't swim in the Delaware River around Philly
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Illustration: Lindsey Bailey/Axios
The Delaware River may look tempting during a hot Philly summer, but a new study emphasizes that swimmers are better off heading upstream.
Why it matters: Swimming in contaminated water can cause stomach illnesses, eye infections and skin rashes.
State of play: A report this week from the nonprofit PennEnvironment found potentially unsafe contamination levels along nearly all of Philly's stretch of the Delaware River.
- E. coli levels exceeded federal standards at 37 out of 43 testing locations on at least one day, per the analysis.
- Water quality was far better north of the city, including areas as close as Bucks County as well as farther up into the Poconos.
How it works: PennEnvironment analyzed federal E. coli monitoring data at more than 650 monitoring locations in Pennsylvania rivers, streams and lakes in 2024 and 2025.
What they found: Roughly 55% of sites statewide had potentially unsafe contamination levels on at least one day.
- That included other locations in the Philly region, including sections of French Creek, Brandywine Creek and Red Clay Creek.
Zoom in: Philly's stretch of Delaware River isn't so different from a giant toilet.
- 12.7 billion gallons of untreated sewage and polluted stormwater are estimated to flow into the river annually.
Plus: Other hazards for would-be swimmers: strong currents, deep waters and submerged obstacles.
Yes, but: Philly's Delaware River isn't completely off-limits.
- Certain recreational activities are permitted, like boating and fishing, where bodily contact with the water is unlikely, per the Delaware River Basin Commission.
- However, significant sewage overflows can make the waterway unsafe for any recreation for several days.
☝️ Pro tip: Avoid the Delaware River after heavy rain — whether for kayaking or letting your dog take a dip, PennEnvironmental spokesperson Stephanie Wein tells Axios.
- Heavy rain can overwhelm Philly's sewage system, increasing the likelihood of overflows into the river.
Worth noting: The city's Water Department doesn't recommend swimming in any of the city's creeks or waterways.
What they're saying: Wein says pollution levels in the Delaware River around Philly will remain elevated until the sewage overflows are reduced.
- "Philadelphians shouldn't have to go to the Jersey Shore or Poconos to enjoy swimming. They should be able to do it right here in Philly like other big cities," she said.
Go deeper: See a map of all the sites PennEnvironment tested