Crews raced against time to stabilize 70-foot-deep sinkhole in Grass Valley

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.

John Gulserin, manager of Nevada County’s Office of Emergency Services, said the sinkhole appeared during last week’s storms behind Liberty Motors on Freeman Lane, south of Highway 20 and just west of Highway 49. It appeared to have been caused by a failed culvert, buried 70 feet below ground.

“It looks like it rusted out,” he said

Tim Kiser, Grass Valley public works director, said the approximately 7.5-foot-diameter pipe was installed in the mid-1980s to handle storm water for development in the area. It carries some water most of the year and empties into Wolf Creek.

Excavation began Saturday to stabilize the slopes and cover the area with plastic tarps to prevent damage to neighboring property with the arrival of more storms.

Kiser said about a 20-foot flat area for equipment was created 12 to 14 feet above the pipe to provide access to clear the culvert ant prevent flooding if it becomes clogged during the storm.

Crews spent the past two days working to cover the excavated area with plastic tarps to prevent erosion, Kiser said.

“I’m as confident as I can be,” he said, that the work done over the past several days will prevent damage during the latest storm.

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