LOUISVILLE, Ky. (WDRB) -- A WDRB Investigation finds dangerous levels of disgusting Ecoli in a popular swimming area. In this special assignment report, Sterling Riggs reveals what’s in the water at Cherokee Park.

For decades, people have flocked to Big Rock to beat the summer heat.

"It's just a spot that, if you are from Louisville, everybody knows about," said Louisville resident Bruce Dale.

"It's a good, mellow swimming hole," said Chris Durham from Detroit, Michigan.

The water in Beargrass Creek may look inviting, but the naked eye can't see the harmful E.coli lurking below. This popular spot is one of Louisville's most-polluted swimming areas.

It is not safe to swim in the water if the E.coli level is more than 400 CFU's per 100 milliliters, according to state standards.

Here's what WDRB found during three months of testing:

In August, the water was more than six times the acceptable standard at 2,419.

In September, the number dropped drastically to only 8, which is acceptable.

But in October, the number shot back up to 2,419.

It's important to note that E.coli levels drastically increased after heavy rain. They were acceptable during times of little to no rain.

David Wicks is a local environmentalist who has been monitoring local waterways for nearly 40 years.

"There’s a problem at this spot called Big Rock. It's almost an attractive nuisance," said Wicks.

He was part of a group that did an extensive study of the water at Big Rock from 1999 to 2008.

"I think there was one sample out of the ten years that it was safe for swimming. I would not swim here! The land that surrounds the creek is what determines the water quality," said Wicks.

Think about it like this. Cherokee Park is a big bowl and the creek is at the bottom of the bowl. Dog Hill is at the top of the bowl and when it rains, items on the ground wash into the water. Seneca Golf Course is also at the top of the bowl.  When it rains, fertilizer washes down into the creek.

Louisville's sewer system also contributes to elevated E.coli levels in Beargrass Creek. The city operates a combined sewer system which handles both storm water and sanitary waste. During storms, treatment facilities overflow and contaminated water ends up in local creeks.

Metropolitan Sewer District officials know there's a problem.

"Truly overflows will not be eliminated. That's a common misconception because we will always have a greater storm than we are designing these solutions for," said MSD Planning Manager Stephanie Laughlin.

To help lessen the problem, MSD signed the Consent Decree with the Environmental Protection Agency in 2005. It’s a legally-binding document to control overflows and build new infrastructure to control water capacity. But, the project won't be finished until 2024.

Will the Beargrass Creek water ever be safe enough to swim in year-round?

"There's a lot of work to do and I think that we are going to have to continue to push and work. I don't know if it's going to be in our lifetimes," said MSD Program Manager Wesley Syndor.

If you have a question about whether a local waterway is contaminated, look for posted signs.  There's one near Big Rock, warning people that swimming after heavy rain can be hazardous.

We found visitors either don't pay attention to the sign or don't care the water could be contaminated.

"I saw a little sign about the rain, but I didn't pay much attention to it," said Chris Durham.

We asked if one swimmer if had ever given any thought to what's in the water? "No. I've swam in other things that are a lot worse,” said Cody Burgess.

Another swimmer put it this way: "If I die at Big Rock or get sick playing in the water, so be it," said Bruce Dale.

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