In a matter of minutes, a dozen cars were pulled over on southbound Highway 99 with flat fires Tuesday morning.
They’d all driven through a large pothole in the slow lane south of Tuolumne Boulevard or hit the chunks of concrete that came from it, said California Highway Patrol Officer Chuck Leon.
The CHP was alerted to the hazard about 7:55 a.m. when callers reported that cars were lined up on the shoulder with flats.
Leon said that by the time he arrived, at least 10 cars were on the side of the road, all with one or two flat tires and some with bent rims.
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The hole was about 5 feet wide by 3 feet long and 10 inches deep.
Winter months are particularly hard on roads, said Angela DaPrato, spokeswoman for the California Department of Transportation. She said water seeps through cracks and sometimes freezes, which causes pavement to expand. When it dries, an air pocket is created and eventually the pavement collapses under the pressure of the vehicles traveling on it.
Leon said it was likely that a big rig tire created such a large hole Tuesday.
The slow lane was closed from central Modesto south to the Tuolumne River Bridge, and traffic backed up well into north Modesto during rush hour. The onramp to southbound Highway 99 from Tuolumne Boulevard was also closed. The highway lane and the onramp reopened about 1:30 p.m.
Leon said the flat tires did not cause any crashes, but several cars were involved in fender-benders due to the backup. No one was injured.
Caltrans filled the pothole with a concrete mixture and will monitor it for future damage, DaPrato said, but a more permanent fix is in the works.
A $7.7 million project will remove and replace the asphalt and concrete on three Highway 99 bridges: over the Tuolumne River, Ninth Street and Seventh Street.
Depending on when the project is approved, DaPrato said, construction will begin in 2019 to 2021.