Clearly, he thought, more than a shovel was needed for such a big task.

But two hours later, the 28-year-old Boeing engineer marveled at how much he and some 280 volunteers accomplished before sitting down to a picnic lunch Saturday: The hill, now cleared of blackberry bushes and other invasive plants, was ready for mulch — the second of a three-part process that, if all goes well, will restore habitat for fish and wildlife and ultimately make Puget Sound a little healthier.

"This is my workout for the day," Hallissy said good-naturedly. "I'm regretting yesterday's (exercise) workout. It made it that much harder!"

An estimated 1,000 people turned out Saturday to pull weeds, lay down mulch and plant native vegetation at 12 sites along the Duwamish, which flows into the Sound. The event's main organizer, People for Puget Sound, billed it as part of "Earth Month," since Earth Day is April 22.

Executive Director Kathy Fletcher noted that People for Puget Sound has been working to restore the Duwamish since 1994, "when it was basically an industrial wasteland."

"Bit by bit, we've been putting it back together again so that now, when you go up and down the Duwamish, you see green vegetation, side channels and streams where fish and birds can thrive, and people enjoying the river — something you hadn't seen for a very long time," Fletcher said.

As she spoke, another volunteer, Richard Strickland, walked by with a shovel and enthusiastically told her, "This is the biggest group I've ever seen doing this." Strickland, an oceanography professor at the University of Washington, was joined by 25 of his students, who received extra credit for participating.

"Extra credit never hurts, and since it's for a good cause, it's nice," said Allison Myers, a UW freshman from Tucson, Ariz., who plans to major in oceanography and environmental studies. "The environment is a huge deal for me. I think that now everyone is becoming more aware."

Serina Shervey and Elizabeth Albrecht, both in the fourth grade at Tukwila Elementary School, pulled weeds under the supervision of Tiffany Ryan, from Seattle Inner City Outings, which encourages children to enjoy the outdoors. The 10-year-old girls seemed to enjoy their work.

"It helps the environment," Albrecht said. "If we don't save it, then some of the polar bears will go extinct."

"No," Shervey corrected. "It's also good for the whole world."

Amy Martinez: 206-464-2923 or amartinez@seattletimes.com