Evanston beaches to use new bacteria testing system this summer

Audrey Cheng

As Evanston’s beach season officially begins Saturday, city health officials are looking for a better way to predict high levels of bacteria in order to shut down disease-prone beaches before swimmers hit the water.

Currently, the Evanston Health Department collects 100 milliliter water samples every summer morning from city beaches to test for bacterial levels. The samples sit in an incubator for 18 hours, and officials read the E. coli level the next morning. If the number of bacteria exceeds 235 parts per 100 mililiters of water, the beach is then closed.

This year, the city will enter the data from previous summers into software designed by the U.S. Environmental Protection Agency and U.S. Geological Survey, said Carl Caneva, the city’s health division manager. The software will list a number of factors and create probability equations to determine beach closures to individual beaches. In addition, the city launched a text and email notification system Wednesday to alert residents of beach closures, according to a news release.

“We’re going to continue to do the bacteria sampling, but what we’re doing this summer is test out equations to see which ones predict the closure of a beach the best,” Caneva said.

He said the goal is to implement the new model next year to predict beach closures early on, so that residents will learn of high levels of bacteria prior to entering the water rather than waiting hours to learn of the risk. Officials have to test out several models this summer to find the most accurate one, Caneva added.

Bob Bechstein, president of the Evanston Windsurfing Association, said the city needs to improve its testing method.

“We need a kit that a lifeguard can use like a pregnancy test,” Bechstein said. “You put it on a stick and you test it and immediately you see results.” Medill Prof. Eric Ferkenhoff, who has previously produced stories on bacteria levels, said he also wishes the testing was immediate. Ferkenhoff said he found residents that were not finding out about bacteria in the lake “until after the fact.”

“You swam on dangerous days and you didn’t swim on undangerous ones,” Ferkenhoff said. “So I’m glad technology is finally catching up. It’s been a long time.”

Caneva said he hopes the new program will be successful this summer.

“If you have a beach that closes for one week (because of high bacterial levels), then you can get a pretty decent model out of it,” Caneva said. “None of our beaches have done that, so we’re just not sure. We’ll just see what this summer brings.”

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