LOS ANGELES (CBS) — Labor Day may have come and gone, but leftover trash and waste in one of the Southland’s biggest parks has left local campsites filthy and could even be contaminating your drinking water.

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As much as 30,000 pounds of refuse was found in just one canyon of the Angeles National Forest in the wake of the holiday weekend, according to park officials.

KCAL 9’s Kara Finnstrom reports a small group of U.S. Forest Service workers and volunteers are still trying to make a dent in the amount of Labor Day litter.

Nathan Judy of the U.S. Forest Service said the concern is not just with trash this that ends up alongside roads and in campsites — it’s also the trash that ends up clogging up the San Gabriel River.

“Approximately 35 percent of L.A.’s drinking water comes from this river,” said Judy. “To pollute it up here where it begins is a travesty.”

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While the city’s drinking water is filtered below, volunteer river watchers also monitor bacteria levels to assess just how much damage has been done.

“The trash content, the feces content that’s in here is high,” said Judy.

So Judy — who knows his small brigade is not enough to tackle this growing problem alone — is educating and recruiting younger park visitors in the hopes they can make a difference.

But after the mess from last weekend, Judy is just trying to keep the faith.

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“It’s heartbreaking when you pick it up and it comes back the next weekend,” he said.