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Galen Rupp grew up in Oregon, so when he sees rain falling the way it did on the first day of Olympic trials, he sees an opportunity, not a roadblock.

No wonder, then, that with rain pounding the track, Rupp was at his best. Running the 10,000 meters in a downpour Friday, Rupp still set a trials record, finishing in 27 minutes, 25.33 seconds.

Next, he'll be off to another place where they know a little about rainy days — London — for a trip to his second Olympics.

"I wasn't worried about it at all," said Rupp, who often has to wear a mask when he runs to keep his allergies from acting up. "I'm from Oregon. I love running in this weather. It's good for my allergies. I was excited to see it was really raining."

His was the most impressive performance on opening day in rainy Eugene, save possibly for the effort decathlete Ashton Eaton put in. With Bruce Jenner watching from the stands, Eaton made it through the first five events on pace to break a 20-year-old American record held by Dan O'Brien.

Later, in the women's 10K, Amy Hastings won in 31 minutes, 58.36 seconds to get the Olympic spot denied her when she finished fourth by 1:11 at the marathon trials earlier this year in Houston.

"Coming across the finish line today, it was night and day different," Hastings said. "It was heartbreaking in Houston. I can't even believe it right now."

While the long-distance runners and decathletes were grinding, the sprinters used Day 1 to warm up — not a bad idea considering the wet chill that gripped Hayward Field all day long, leaving puddles on the track and turning parts of the infield mushy.

Sanya Richards-Ross, LaShawn Merritt, Allyson Felix and Carmelita Jeter all made it through their opening heats with minimal problems.

"Other than it messing up my hair, it's OK," Richards-Ross said after running her first 400-meter qualifier in 51.69 seconds.

Merritt, the defending Olympic champion at 400 meters, took to the rain-slickened track, sidestepped a runner who slipped and fell in the lane next to him and finished in 45.36 seconds, the best time in the men's heats.

"I saw him and I had to do a little step more toward the inside of my lane, where I should've been in the first place," Merritt said.

Jeremy Wariner, the 2004 Olympic champion, also advanced to the semifinals, though his race wasn't quite such a breeze. He finished third in his heat in a time of 45.84.

"Just clearing the cobwebs out," Wariner said. "I worked my turn pretty well. I saved a lot for the homestretch."

David Neville, the 2008 Olympic bronze medalist, finished last in his heat and won't go to London unless he is chosen for the relay team.

The 400 runners have semifinals Saturday, with finals scheduled for Sunday.

In the women's 100, Felix and Jeter each won their heats easily.

"It was OK. Just wanted to make it safely to the next round," said Felix, who is using the 100 to stay sharp for her main event, the 200. "I feel like tomorrow will be better. Always good to get that first one out of the way."

In the women's 100 hurdles, Dawn Harper, the defending Olympic champion, won her heat in 12.79 seconds — a victory she earned even though she didn't have the ideal, track-grabbing spikes in her shoes.

"I actually change spikes" when it rains, she said. "Usually, the pointier ones grab the track. It was on my mind out there because I had the older ones in."

Lolo Jones also qualified but not by much. She finished third in her heat for the last automatic qualifying spot after running 13.01. Her race was delayed when Shericka Ward false started.

"I felt really good, but it was a bad race," Jones said. "After the false start, I just relaxed a little bit too much."

Meet organizers scrubbed women's pole vault preliminaries, meaning all 29 athletes, including 2008 Olympic silver medalist Jenn Suhr, will move to finals Sunday.

In the decathlon, Eaton was ahead of a world-record pace for two events. His shot put throw of 46 feet, 7 3/4 inches slowed him down, but he still ended the day with 4,728 points — 322 ahead of Trey Hardee and 17 ahead of the pace O'Brien was on when he set the American record in 1992.

"This is the culmination of a lot of hard work my team has put in," Eaton said.

Eaton, an Oregon native, also closed the day by running in the pouring rain, finishing the 400 meters in 46.70 seconds. He looked very much at home.

As did Rupp, who will be joined on the 10K team by Matt Tegenkamp (27:33.94) and Dathan Ritzenhein (27:36.09).

After many months filled with injuries and the heartbreak of missing the marathon team by 8 seconds, Ritzenhein needed to beat the 'A' standard of 27:45 to qualify in the 10K. He did and made his third Olympics.

"It's been a rough road," he said. "The last few years have been very difficult, for sure."

So while he celebrates a spot in the Olympics, most of the rest were simply glad to still be in the hunt — advancing on a slip-and-slide kind of day, knowing that under U.S. rules, the top three qualify — no excuses or second chances, no matter the conditions.

"You have to adapt to what the weather is, how the track is," Merritt said. "Know what you're doing before you get out there. You know the weather, the wind, and the track is slippery. It's all about going in with a plan and executing."