VALENCIA (CBS) — Local environmental groups have issued a stunning accusation against Six Flags Magic Mountain, claiming that the popular theme park is polluting the Santa Clara River.

“They have the best rides,” said Chris Murray, who spent a fun day at the park with friends.

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But some environmentalists claim the fun theme park has a dirty secret, polluting the nearby Santa Clara River.

“We were surprised to see, to hear actually, from an employee at the park and several community members, that they thought that there was some pretty serious population coming off Magic Mountain,” said Liz Crosson, the Executive Director of Santa Monica Baykeeper.

“We found really high levels of things like toxic metals. We found a lot of trash, unfortunately, it’s really pretty gross down by the river right next to the facility,” Crosson added.

Wishtoyo Foundation’s Ventura Coastkeeper Program, Santa Monica Baykeeper, and Friends of the Santa Clara River started investigating the theme park last year.

“We had a whistle-blower come to us, who was concerned about the park’s practices, wash-down practices, after operating hours. And we went out to investigate. And we found from Magic Mountain’s own water quality monitoring reports during storm events and our own monitoring events, that the quality of the water being discharged into the river was much worse than we could have imagined,” said Jason Weiner with the Wishtoyo Foundation.

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The group captured photos of trash in the river, which heads out to the Pacific Ocean. Much of the debris scene in the photos has Magic Mountain’s logo on it.

The environmentalists said they are ready to take legal action.

“We’ve issued Magic Mountain a 60-day notice of intent to sue under the Clean Water Act,” Weiner said.

Six Flags released a statement to the L.A. Times, saying that it was “concerned about the environment and feels a responsibility to improve the storm water process.”

It went on to say that the company has spent hundreds of thousands of dollars over the past six years to lower storm water discharge and improve the quality of the discharged water.

The alliance said that it sent Six Flags Magic Mountain a letter last Friday with 20 pages of violations and concerns. They said that they had not yet heard back from the theme park.

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Our calls to reach Magic Mountain representatives were unsuccessful.