Beaches stay closed for third day in a row amid bacteria concerns

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All Evanston beaches remained closed to swimming again on Wednesday, the third consecutive day of shutdowns after a historic rainstorm hit the Chicago region on Sunday.

While the sand portion of each beach was open, poor water quality caused by elevated levels of E. coli and other bacteria resulted in the swim ban. That bacteria entered the lake when the Metropolitan Water Reclamation District (MWRD) had to open the Wilmette and downtown Chicago “control structures” or “locks” to alleviate flooding on Sunday, which allowed a combination of excess sewage and storm water to flow into Lake Michigan.

Evanston saw more than seven inches of rain that day, July 2, while other parts of the region got nearly nine inches.

“There is no system able to handle that much water in just a few hours,” the MWRD said in a storm aftermath update on Wednesday, July 5.

Chicagoland has an underground combined sewer system, rather than a separated one, which means all storm water and sewage go to the same tunnels, reservoirs and treatment facilities. As a result, when overflows force the locks open because of major storms, sewage gets into the lake near Evanston, because the Wilmette lock is located just north of us, next to the Baháʼí Temple.

Perhaps most importantly, the MWRD can only reverse the flow of excess water toward the lake when the Chicago River level becomes higher than Lake Michigan.

“If we were to open the lock and gates too early, Lake Michigan would have a tsunami effect, overtaking the river and flooding everything in its path in downtown Chicago and along the waterways, totally decimating the riverwalk and municipalities downstream, on the South side and on the North side,” the organization said in Wednesday’s press release. “The destruction that would be caused by opening the gates and lock too early is unimaginable.”

The other alternative would be for the MWRD to leave the locks untouched, which would cause diluted sewage water to force its way out of underground tunnels through manholes on streets all around the region. As a result, opening the locks and letting some sewage into the lake offers the least dangerous of all evils in these storm situations.

In the past, beaches in Evanston, Chicago and other lakefront cities have had to close more frequently because of this phenomenon. But, starting in 1975, the MWRD began construction of the Tunnel and Reservoir Plan (TARP), often simply called “Deep Tunnel.”

Over the past 50 years, TARP has become one of the largest civil engineering projects in the world, digging more than 100 miles of underground tunnels thus far with a combined sewage capacity of 2.4 billion gallons. The project is still underway today, with the ultimate final capacity expected to reach 17.5 billion gallons. But even with that massively expanded capacity, “it will still be possible for the system to fill during extreme storms,” according to MWRD’s information page on TARP.

“To combat this [sewage overflow], we have partnerships with municipalities and other organizations throughout the county to fully or partially fund green infrastructure and other stormwater projects to improve resilience within that community,” MWRD said Wednesday. “The 34 Space to Grow green infrastructure projects that convert asphalt into permeable surfaces at local schools is just one example of a partnership improving communities one neighborhood at a time.”

More details about the Chicago Area Waterway System are available here, as are the full list of times the locks have been opened since 1985 here.

MWRD also offers both virtual and in-person water reclamation plant tours. Register online here.

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Duncan Agnew covers Evanston public schools, affordable housing, City Hall and more for the RoundTable. He also writes long-form investigations, features and the morning email newsletter three times a... More by Duncan Agnew