PROSSER -- Sixty homes lost water early Thursday after a water tank pipe in the hills above town burst, unleashing almost 1 million gallons.
Authorities weren't certain Thursday what caused the water main break that flooded the cemetery and a track at Prosser High School and sent muddy water flowing into downtown.
"(Determining costs) usually takes a couple of days as people are cleaning up," said Steve Zetz, Prosser city planner.
A resident called police about 3 a.m. to report water in the road near a home.
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The water -- equal to about 1 1/2 Olympic swimming pools -- washed out a gravel road as it headed over Highway 22 and downhill to the cemetery.
The water then traveled down Paterson Road into town. Zetz said Paterson Road does not have storm drains, allowing it to act as a water chute.
State transportation officials shut down Highway 22 from 5:30 a.m. until after 7 a.m. to clear debris caused by gushing water.
Water service was restored to area homes by Thursday afternoon.
Prosser School District Superintendent Ray Tolcacher said floodwaters overwhelmed the drainage system in the district's parking lot and athletic facilities on Paterson Road. Water bubbled up in the drains and covered the football field and flooded most of the track.
Track practice was canceled Thursday but the track could be ready for today. Cleanup efforts haven't begun yet and it's not clear what the damage might be.
"(Tracks) aren't meant to have water go underneath them," Tolcacher said.
The schools lost water pressure, but classes were not in session because of parent-teacher conferences.
Zetz said the burst pipe coming from the 3 million-gallon reservoir was installed in the mid-'90s and the rupture split off a 6-foot piece. The incident did not contaminate the town's water supply.
The damage was most visible at the Prosser Cemetery, where graves in the older section, with upright markers, were covered in 8 inches of mud, reported the Yakima Herald-Republic.
"This is now known as the great cemetery river," said John Koenig, a cemetery employee, as he cleared some of pavement paths with a small tractor.
Cemetery director Tim Stewart told the newspaper that cleanup will take about a month but none of the graves will have to be dug up. The biggest problem will be sinkholes underneath the old wood caskets that have long since decayed.
Among the flooded graves is the resting place of May Mathews, a 6-year-old girl buried in 1901. The story goes, Stewart said, she suffocated during a sandstorm high in the Horse Heaven Hills.
Anyone with flood damage to report can call city hall at 509-786-2332 or go to www.cityofprosser.org.