"What we are talking about is e. coli contamination that is basically sewage overfill into our waters."
Henderson said heavy rains are to blame for the high levels of bacteria. While he doesn't swim in the lake, many people do- as long as they've got the green flag from the Chicago Park District.
" It's good to come in and go waist deep, wade around and play to cool off and come back to the sand and enjoy the sun but probably not to swim in it and be in it for a long period of time," said one person on the beach.
"A couple days out of the year, I don't think will hurt them much. The food is probably worse than the water they're swimming in," said another.
"I grew up in Missouri where you would swim in creeks and lakes that the cows had been in," said a third woman on the beach.
The NRDC says Chicago does a good job of testing, but the EPA standards the city must follow are outdated and are not timely because results take 24 hours. The environmental group is calling for tougher federal standards.
"It's a very valuable asset we have here in Chicago and we should do everything we can to keep it that way," said one Chicagoan.
The NRDC said swimming in contaminated water can lead to gastrointestinal and respiratory problems. The Chicago Park District said there have not been reports of people getting sick from the lake water.
The NRDC report said that one of Chicago's North Side beaches had the highest number of closures in the nation. The park district disputed that report and the NRDC said the group got some numbers wrong.