CONCORD — Two national records were broken Saturday in one of the fastest meets in North Coast Section swimming history.

Campolindo High’s Steven Stumph and Carondelet’s 400-yard freestyle relay team each etched their names into the national high school records books with their performances Saturday at Concord Community Pool.

Though he’d just tied the national record the day before, Stumph stepped on the blocks for the breaststroke final knowing victory wasn’t a given. The senior wasn’t the only one with his eye on Olympian Brendan Hansen’s record.

In one of the most electric NCS races ever, Stumph held off Miramonte’s Charlie Wiser and Granada’s Nick Silverthorn as all three swimmers went under Hansen’s previous national high school record of 53.67 seconds. Stumph was the winner in 53.39 while Wiser took second in 53.57 and Silverthorn was third in 53.61.

“I knew both Nick and Charlie were going to push me to do my best, and they definitely did,” said Stumph, who is headed to USC. “I couldn’t have asked for a better race. … It was amazing all the positive energy coming from the crowd, the announcers, and my teammates.”

“I haven’t seen anything like it,” Campolindo coach Ron Heidary said of the breaststroke final. “I think the consensus from everybody I talked to was that was the most extraordinary heats of swimming that anybody has ever seen.”

It was a day full of wins and records for Stumph, who also won the 100 butterfly in a NCS record and helped the Cougars’ 200 medley and 400 freestyle relay teams to new meet marks. Not surprisingly, the Campolindo boys took home the team title for the ninth consecutive year.

“It’s incredible knowing everyone played a part and we did it as a team,” Stumph said.

Carondelet also earned a team championship along with its national record. Their 400 freestyle relay team, made up of Chelsea Chenault, Natalie Amberg, Madelyn Murphy and Madison White, finished in 3:20.42, which was better than the 3:21.63 set by Pennsylvania’s Germantown Academy earlier this year.

Chenault, who also swept the girls 200 and 500 freestyle for the third time, gave Carondelet a huge early lead in the relay with her 49.27 leadoff leg. That swim will go in the books as the new NCS 100 freestyle record, topping Olympian Kim Vandenberg’s mark from 2000 and giving Chenault three individual section records total.

Chenault said the national record and team title were a great way to end her decorated high school career.

“Losing (the team title) two years in a row really humbled us because we were on cloud nine after my freshman year,” Chenault said. “It was good to see other teams do well, see what they can do and really support them, and then have our time my senior year.”

Las Lomas senior Jackson Miller earned NCS records in winning the boys 200 and 500 freestyle while Amador Valley’s Iris Brand was also a double winner, taking home titles in the girls 50 and 100 freestyle.

Miller toppled the oldest NCS boys record still standing when he posted a time of 4:23.85 in the boys 500 freestyle final to beat the mark John Dorr set in 2000. The NCS 500 freestyle record once belonged to Miller’s uncle who swam for Las Lomas back in the 1980s.

“Back when I was a freshman I told him I was going to get it back in the family,” Miller said. “It felt good to finally break that, go say hi to my uncle and share that with him.”

Miller was pleased with his individual swims, but said the highlight of his day was celebrating the 200 freestyle relay title with his teammates.

Foothill’s Celina Li and Carondelet’s White were each successful in defending one of two individual championships. Li won the 200 individual medley but lost the 100 butterfly, an event she set a meet record in last year, to Albany sophomore Ariana Saghafi.

White won the 100 backstroke for a third straight year, though Brand beat her out for the 100 freestyle title.

The meet ended with a thrilling finish in the boys 400 freestyle relay. Sven Campbell chased down his Granada opponent in the final 50 yards to give Campolindo a win by .03 seconds. His relay split was 43.87.

“I really think that was the best swim of his entire life,” Heidary said of Campbell. “He was sick, he was struggling physically and to come back with a 43 split, it was almost a herculean effort in my mind. It was unreal. It’s a credit to him and his mental toughness.”

Campbell, ailing from the flu, also won the boys 50 freestyle but took second to Amador Valley’s Jason Chen in the 100 backstroke after winning the title as a sophomore and junior.

Other individual champions were San Ramon Valley’s Heidi Poppe (girls 100 breaststroke), Heritage’s Ryan Barsanti (boys 100 freestyle) and Wiser (boys 200 I.M.).

In the team standings, Granada was the runner-up on the boys side while the San Ramon Valley girls had to settle for second after winning the past two titles.