State and local government agencies often hire the teams to improve public parks, trails and wetlands.

On weekends, several 10-person crews gather at a central camp for hiking, rafting and other outdoor recreation.

In Joryville Park, Enos and others spent the day building a footbridge -- from scratch.

They built the concrete forms, poured the foundation and cut the treated beams with chainsaws.

Tom Prang, the crew leader, told a few teens stabilizing the base of the bridge to switch with two who were bolting planks of wood together.

Each crew has five girls and five boys.

'Ladies, it's time to do some shoveling,' he said. 'Gentlemen, I've got some washers here.'

At 2:30, the sweaty teens had put in almost a full day of work. They wake at dawn and get to shoveling, raking, cutting and chopping.

One exhausted Sprague High School student, Erin Brennan, paused from gathering cut branches to get water.

'My feet hurt,' she said.

Last summer, Enos cut blackberry bushes, built trails and restored wetlands. She enjoyed a long backcountry trip to build hiking trails.

'It's really worth it when you get up there,' Enos said, 'because the places you hike to are the most beautiful places.'