The sound of chain saws ripped through the morning air as Casper firefighters began sawing down Russian Olive trees along the North Platte River Wednesday morning, marking the beginning of the Platte River Revival.

Part of the several-year movement to clean up the North Platte River is to remove most of the prickly, water-sucking trees from the river banks and give native breeds a chance to grow.

Russian Olive trees were recently declared a noxious weed by the USDA and are a non-native, invasive species that breaks down the natural ecosystem, said Revival coordinator Jolene Martinez.

Casper Fire Department Engineer Jim Barton said the work will help the other trees thrive.

"They are doing this in other areas of the country too," he said. "I know in the Grand Canyon they are cutting out the Russian Olives because they use so much water."

After the trunk falls, an herbicide called Garlon4 is applied within 15 minutes, killing the stump and roots.

"If we don't kill the root system they will be back next year and bigger than this in several years," Casper Fire Chief Mark Harshman said, pointing to a large tree by the river. "The stump seals over pretty quick after we cut the tree and so someone needs to follow behind to spray."

Casper firefighter Jim Maddox stopped briefly to fill his chainsaw with gas and said after six years on a hot-shot crew fighting wildland fires, each tree is still a challenge to cut.

"Every tree is different, because they grow differently, the wind changes and they lean in different ways," he said, placing his foam plugs back in his ears before beginning again.

Some of the larger trees were allowed to remain standing but were pruned to provide shade access underneath and protect people from the spines and branches.

This was the first of many tree removals, spanning from the Whitewater Park to Brian Stock Trail.

The trees were cut into roughly four-foot sections, and stacked on the banks of the river. During the Platte River Revival cleanup day on Sept. 22, volunteers will remove the piles of branches.