Skip to main content

Chicago River Swim

Sunday, September 22, 2024

Water Quality



Swimming in the Chicago River may sound like a wild idea, but the river has come a long way from its industrial past. Today's water quality results suggest that it's not as crazy as it seems.

Through concentrated efforts, the Chicago River is at its cleanest levels on record. Advocacy groups like Friends of the Chicago River have worked for 50 years to clean up and celebrate the unique resource that is the Chicago River, and the turnaround has been remarkable. The river is constantly moving toward greater biodiversity, and is now home to countless wildlife including more than 80 species of fish.

Additionally, the river's main channel is fed directly from Lake Michigan. Every time the Chicago Harbor Lock opens, more than 250,000 gallons of lake water flow into the Chicago River and head downstream. The event's swim course will be set entirely in the main channel.

The Chicago River is a self-sustaining ecosystem whose health is directly impacted by weather patterns and environmental activity. Water quality readings are typically positive, however there are occasions where conditions are less than ideal. Like any organized open water swim or sanctioned triathlon, the Chicago River Swim will only operate in waters that are deemed safe for human exposure.

The Chicago River Swim will be monitoring water quality statistics throughout the season by using published data from established experts in that field, including the Metropolitan Water Reclamation District (MWRD) and Current's H2NOWChicago waterway monitoring system.

MWRD tests measure microbial pollutants such as e. coli and fecal coliform (FC) -- a reliable analog for bacteria that could be harmful to anyone with direct contact with the water, including swimmers. The H2NOW platform utilizes leading-edge sensing and analytic technologies to measure water quality and communicate them to the public in real-time. In-season data can be viewed at

H2NOW monitors river temperature, turbidity (cloudiness or clarity), specific conductivity (salinity), colored dissolved organic matter (CDOM), and tryptophan-like fluorescence (TLF) with Proteus multiprobes in each branch of the Chicago River. Current also collects river samples on a near-daily basis from each branch of the Chicago River and tests them for harmful bacteria using a specially-designed analyzer. The real-time data, collected and transmitted every 15 minutes, feeds a model that estimates FC numbers at each site and produces a water quality assessment. The FC tests conducted continuously during the recreational season help verify and adjust the model, if necessary, in order to deliver to the public the most accurate assessment possible.

The Chicago River Swim will continue to monitor conditions and ultimately make decisions while using this publicly-accessible data. During the warmer season, data from both MWRD and H2NOW will be shared on this site.

The Chicago River Swim will follow the EPA's 2012 Water Quality Recommendations for e. coli presence in freshwater swimming, set upon a geometric mean of 126 cfu/100mL, and a statistical
threshold value of 410 cfu/100mL. The event will utilize a decision matrix, relative to multiple test results over time, in order to conduct a Go/No-Go decision on the event.


In the event of heavy rains or other environmental issues that might cancel the September 22 event with enough notice, organizers hope to gain approval of a back-up date scheduled for Sunday, October 6 (two weeks later). 

Additional details will be posted on this page as the event draws nearer.

If you continue to use this site, you consent to use all cookies. We use cookies to offer you a better browsing experience. Read how we use cookies and how you can control them by visiting our Privacy Policy.

If you continue to use this site, you consent to use all cookies.