Mud coating the Stadium Bowl up to a foot deep in one area could take up to three weeks to clean up.
A gully washer Sunday afternoon sent water cascading down the stairs and inundated Stadium High School’s football field.
The storm was brief but very intense, said Mike Slevin, Tacoma’s environmental services director. The rainfall overwhelmed the city’s stormwater system.
“For that type of overload conditions, it performed well,” he said. “Our system will never be designed for that intensity of storm.”
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The skies opened just before 4:30 p.m. The National Weather Service said Sea-Tac Airport received 0.17 inches of rain Sunday through 5 p.m., but gauges closer to the bowl showed higher totals.
In less than a half hour, more than a half-inch of rain had fallen, according to a rain gauge at the Central Wastewater Treatment Plant less than two miles away. Slevin said he thinks that amount of rain actually fell in 15 minutes, but the gauge records only in 30-minute increments.
Slevin said the water followed an old creek basin, which leads to the Stadium Bowl. Other parts of Tacoma did not see such intense rainfall, he said.
Nearby, at the Spanish Steps in downtown Tacoma, a recently upgraded storm water system performed well in the storm, Slevin said. The area had seen occasional flooding after recent improvements made to Stadium Way, with a deluge swamping a law office along Commerce Street last fall.
After the water from Sunday’s storm receded, about a foot of mud remained in one area of the Stadium Bowl’s field, said Tacoma Public Schools spokesman Dan Voelpel. Altogether there might be three pickup loads of dirt on the field.
Because the field is covered with artificial turf instead of grass, the district will take care to remove the mud without harming the turf, he said.
Already the district has removed some leaves and debris from the field, as well as scraped up mud and rocks from the grandstands.
In much the same way a squeegee would clear a windshield of water, the district’s maintenance crew will use a light tractor equipped with a rubber blade to scrape off most of the remaining mud.
“Once we’ve done as much as we can do with that, we are going to use high-volume but low-pressure water to slowly push the remaining dirt to the track,” Voelpel said.
Community groups often use the field, he said, but none are scheduled during the three-week cleanup period.