Winnetka Stormwater Tunnel: What About The Other 99 Percent of Pollution?

Confirmation bias is selectively using facts that support one’s position while ignoring the ones that don’t.  The Winnetka Home Owners Association (WHOA) is using confirmation bias to support its claims that stormwater does not contribute to beach closures in Winnetka.  Unfortunately, they’re cherry picking these facts from NRDC’s Testing the Waters report.

Testing the Waters does report that 1 percent of Illinois’ reported sources of beachwater contamination comes from stormwater. 

However, in the line directly above that statement, Testing the Waters also reports that 99% of beach closures come from unknown contamination sourcesTesting the Waters makes clear that stormwater is by far the most commonly identified cause of beach closings and swimming advisories across the country.

That finding is supported by the Illinois Environmental Protection Agency (IEPA), which analyzed beach impairments in five communities, including Winnetka.  Its analysis found that stormwater likely has a large impact on Winnetka beach segments and that stormwater typically contains bacteria like Escherichia coli (E. Coli).  E. coli indicates that feces, potentially containing pathogens, are present in the water.  Exposure to E. coli bacteria, along with other viruses and parasites in contaminated beachwater, can cause a wide range of diseases, including ear, nose and eye infections, gastroenteritis and respiratory illnesses. 

That’s why IEPA is requiring these communities -- Winnetka, Evanston, Glencoe, Wilmette and Kenilworth --  to limit bacteria loadings to help make their beaches safe for swimming.

It’s also worth noting that one of the best management practices IEPA identifies, as does Testing the Waters, to help manage stormwater is the use of green infrastructure.  Green infrastructure helps stop runoff pollution by capturing rainwater and either storing it for use or letting it filter back into the ground, replenishing vegetation and groundwater supplies. Examples of green infrastructure include green roofs, street trees, increased green space, rain barrels, rain gardens, and permeable pavement.  Green infrastructure also helps reduce the risk of flooding – a major concern in Winnetka and hundreds of other communities – by literally capturing rainwater where it falls and allowing it to slowly percolate back into the ground or slowing its descent to the sewer system.

Strategies that capture rain are important since rain is often a contributing factor to beachwater pollution. Heavy rain can overwhelm sewage systems, forcing raw sewage directly into coastal waters, bypassing treatment plants. And as rainwater washes over land, it picks up pollutants and carries them directly to coastal waters. According to EPA, pollutants found in stormwater include trash, bacteria, motor oil, pet waste, pesticides, fertilizer, animal droppings, and anything else that washes off developed land when it rains.

The health of our communities – and our beaches – are too important to cherry pick facts to support a narrow position.

About the Authors

Karen Hobbs

Senior Policy Analyst, Water program

Join Us