LEWISTON – During the hours in the basement of her Bates College dorm, cleaning mounds of flimsy, sour-smelling yogurt lids, Catherine Elliott hoped her effort would pay off.

“I got pretty wrinkly fingertips,” said Elliott, an 18-year-old freshman. After four or five hours of washing the tin caps, she’d spend more hours in her room, bending them into tent shapes and stacking them to dry.

In the end, each lid she collected – 4,679 in all – would represent more than $20 for children.

Elliott won the grand prize in a contest run by New Hampshire-based yogurt maker Stonyfield Farm and KaBOOM!, a nonprofit organization that helps fund play spaces for children.

The prize will give $50,000 for play spaces at the Auburn-Lewiston Clubhouse of the Boys & Girls Clubs of Southern Maine. Another $50,000 will go to a school in Maryland, chosen by Elliott and leaders at the Boys & Girls Clubs.

It all started with breakfast.

One morning in November, Elliott noticed the contest on the lid of her yogurt. Then, she noticed the stacks of yogurt in the dining hall fridge. All were from Stonyfield. All had the identical “Enter to Win” blue caps.

“It seemed like too good an opportunity to pass up,” Elliott said.

To the former Girl Scout from Edina, Minn., it became another cause.

“I’m a fairly ambitious person,” she said. “I grew up with a sense of responsibility to the community.”

Her parents, both lawyers, trained her to give even as a little girl. When she was 8 years old, they encouraged her to donate a portion of her allowance to a cause.

“They’d give me 25 cents a week,” she said. “One week a month, I had to give it to charity.”

As a Girl Scout, she won her gold award for organizing a bike rodeo. And just weeks into her tenure at Bates, she volunteered at the Trinity Jubilee Center in downtown Lewiston and at a low-income housing complex a few miles from the college.

Elliott was already busy when she discovered the yogurt contest, but she made time to meet with Christine Schwartz, the director of dining services at the school.

“It kind of humbled me,” Schwartz said. “I didn’t think of it, and I work here.”

Time seemed tight, though.

The two met in early November and there were a few weeks of school before the winter break began. The contest was scheduled to end Dec. 31.

“I thought, ‘We don’t really have a chance,'” Schwartz said. But she met with her staff and created a system for collecting the lids. When students finished their meals, they dropped lids into a collection box. Dining hall workers collected more lids from the students’ used trays.

The spent lids were bagged for Elliott to clean and package.

Elliott had little idea how many she might collect. She was still packaging the lids when her semester ended in December.

The lids went with her to Minnesota for Christmas. She mailed them to Stonyfield from Edina.

And she tried to keep her hopes in check.

It was early February before the yogurt company finally announced the winner. Elliott sat with Andie Hannon, who manages the Boys & Girls Club’s Auburn-Lewiston Clubhouse, in a conference call with Stonyfield.

The call, billed as an interview, became the surprise notice.

When it ended, grown-ups and kids alike cheered.

The Auburn charity plans to redo its gym floor, buy new equipment and clean up a nearby park with the money, Hannon said.

Elliott became the ideal winner, said Chantal Druchniak, spokeswoman for Stonyfield.

In all, about 100 entries were submitted for the nationwide contest. Of all those who entered, Elliott was the only one who didn’t have a connection to the kids she was trying to help.

“She just saw the lids and wanted to chip in,” Druchniak said. “That’s exactly what we wanted.”