For a few hours yesterday morning, the cafeteria at Key School in Annapolis turned into an assembly line, and the sounds of power drills and chattering students filled the air.

Jovaughn Barnard, 14, wielded a yellow handheld drill as if she'd done it all her life. Her manicured nails clicking against the tool, she rapidly drilled small holes on the lid of a 3-foot-tall plastic barrel.

She and dozens of other ninth-graders at the private school in the Hillsmere Shores community were building rain barrels -- contraptions used by some farmers and gardeners to collect rainwater.

"I'm not a handywoman," said Barnard, who had not used a drill before yesterday. But she and her classmates were working expertly by morning's end.

The work party was organized by environmentalists and homeowners to popularize the use of rain barrels, which can reduce storm runoff. Such runoff has damaged the community's waterfront over the years.

As the students worked inside, local residents lined up outside to receive barrels. For a $30 donation to the South River Federation, one of the event sponsors, each homeowner could take two barrels. Seventy barrels were distributed, and eight people signed up on a waiting list.

Placed under a downspout, each barrel can catch and hold about 60 gallons of rainwater. A wire mesh screen across the top keeps out leaves and mosquitoes. A valve and garden hose near the bottom control how much water is released for gardening or other outdoor uses.

A 1,000-square-foot roof can produce 800 gallons of runoff in the worst storm of an average year, according to the federation.

Because the Hillsmere Shores community was built in the 1950s, before the existence of storm-water management regulations, runoff flows unchecked into the area's waterways, eroding the land and filling creeks with sediment.

In some tributaries, sediment from runoff has reduced the water depth to six inches, compared with six feet 20 years ago, said Robert Emmet, president of the Hillsmere Shores Improvement Association, which co-sponsored the project. As a result, underwater life has become scarcer.

As he worked on a barrel, Jeff Roeser, 15, said he hopes the rain barrel concept catches on.

His family moved to the area two years ago, and he has gotten used to playing with his dog near the water. "When you see everything eroding, it's not so nice," he said.