Transportation

Caltrans inspection finds no Highway 49 damage from Grass Valley sinkhole

See the view from the bottom of Grass Valley’s massive sinkhole

A failed culvert appears to have caused a 70-foot sinkhole near an auto dealership in the southwest part of the city of Grass Valley. The city worked over four days to stabilize the the sinkhole before Wednesday's storms. This video shows the sink
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A failed culvert appears to have caused a 70-foot sinkhole near an auto dealership in the southwest part of the city of Grass Valley. The city worked over four days to stabilize the the sinkhole before Wednesday's storms. This video shows the sink

The California Department of Transportation says drilling and underground investigations Wednesday indicated that a failed culvert and sinkhole near Highway 49 in Grass Valley had not undermined the freeway.

Liza Whitmore, a Caltrans spokeswoman, said motorists earlier this week alerted the California Highway Patrol to a depression on the southbound freeway between McKnight Way and Empire Street. The depression, she said, was a quarter- to a half-inch deep and might not have caused concern except for the large excavation around a sinkhole just west of the freeway.

The CHP reported on Twitter that the depression, which began in the slow lane, had extended to the fast lane by Wednesday.

Whitmore said holes 20 feet deep were drilled at three locations in the depressed area of the roadway and no voids were found that would indicate the roadway was being undermined. A video inspection also found the culvert beneath the freeway intact and no leaks were detected, she said.

Whitmore said Caltrans will continue to monitor the site.

The nearby sinkhole off Freeman Lane appeared during storms two weeks ago and was traced to the failure of a 7.5-foot-diameter pipe installed in the 1980s to handle stormwater for development in the area, according to Tim Kiser, Grass Valley public works director.

Excavation crews stabilized the slopes, and the area was covered with plastic tarps in an effort to prevent damage to neighboring property during last week’s storms.

Kiser said permanent repairs and restoration of the Freeman Lane site probably won’t be completed until late spring or early summer.

After a four-day race against time, officials believe a 70-foot-deep sinkhole in Grass Valley is stable enough to weather the storm that moved into the region Wednesday.

Cathy Locke: 916-321-5287, @lockecathy

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