Keeping the water clean is the challenge.
"From State Street and other areas the sewage will run into the lake. We've got paper cups out there, garbage," points out Brett Hulsey of the Sierra Club.
Even though the trash is not theirs, volunteers pick it up.
Barbara Borns explains, "we engage students and other volunteers to go out with garbage bags and simply clean up along the creek."
Past problems prove the efforts are needed.
"A dog died after swimming in Lake Kegonsa last year, so when the beach is closed you really shouldn't swim there," advises Hulsey.
Water is not the only cause for concern, studies show that sand can carry ten times the contaminants. That is why Madison beaches are tested on a weekly basis.
Microbiologist Lyle Kleppe has been taking samples, and testing for bacteria for the last 53 years. His results determine if beaches close.
Holding a sample, Kleppe says, "this one was because there was some algae problem. The supervisor wanted to make sure there was not a bacteria problem there too, but obviously there isn't."
He knows that because the clumps of bacteria do not meet criteria for closure.
"The bacteria have been reasonably good," Kleppe says. "Early on in the year or up until say a couple of weeks ago algae was quite prevalent."
While Kleppe looks out in the lab, grassroots groups keep watch of area waters. If you have concerns about a lake you can let the health department know about it. Beaches are inspected weekly. Currently, all Madison beaches are open for business.