The closure of Interstate 5 south of Tracy in San Joaquin County continued Friday as crews worked to rebuild the roadway in the area where a sinkhole was discovered earlier this week.
Northbound lanes were expected to reopen at midnight Friday, according to a California Department of Transportation news release. Southbound lanes are expected to remain closed until noon Sunday.
During the closure, motorists are being to diverted to Highways 33 and 132, a 6-mile detour resulting in 15- to 30-minute delays.
Caltrans crews performing routine maintenance found the sinkhole on the shoulder of northbound I-5 Tuesday morning, and northbound lanes were closed at noon that day. The initial sinkhole was 1 foot wide by 10 feet deep, but crews had to excavate the roadway to locate the source of the void, Caltrans officials said.
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It was determined that a hole in a 40-year-old, abandoned 36-inch corrugated steel irrigation culvert allowed soil to be displaced, producing the sinkhole under the northbound portion of the highway. Maintenance crews began removing the culvert and that work continued as the pipe approached the southbound lanes.
Southbound I-5 was closed at 7 p.m. Wednesday as crews investigated those lanes for possible signs of failure. Caltrans decided to keep the southbound lanes closed so core samples could be taken to determine the condition of the soil under the roadbed.
Although drilling did not identify voids beneath the surface, the decision was made early Thursday to excavate the southbound lanes and remove the remainder of the culvert. Caltrans officials said excavating and rebuilding the road base was the only way to assure the safety of motorists.
Crews dug down 35 feet to remove the culvert and ensure no additional sinkholes were present, then rebuilt the foundation of the roadway before they began paving, officials said.