Frustrated by lack of helpful underground snapshots, San Pedro’s Clearwater inspection hits delays

Drilling for underground camera access could continue on Western Avenue in San Pedro until the end of the year as county officials grapple now with a drilling machine repair and — so far — no good images of the deep underground landscape to explain why a tunnel under construction sustained a breach this past year.

The tunnel, some 360 feet underground, had been under construction from Carson to San Pedro to install new, larger wastewater pipes to serve the region. It has been suspended since the breach occurred near the end of the line in July.

But the effort to glean more information by lowering remote cameras underground is proving to be challenging.

“It’s far more complicated than we expected, the work is slow and frustrating,” said Michael Chee, spokesperson for the Los Angeles County Sanitation Districts.

The breach occurred underground below Western Avenue at about the Fifth Street cul-de-sac mark — west of Weymouth Avenue and south of where Weymouth curves up to connect with and cross Western. The camera drilling is being conducted on Western, directly above where the underground breach occurred.

“We’ve only been able to bore one hole to (the needed) depth two weeks ago and we had a limited camera view from that first bore hole,” he said. “We’ve been trying to get more sophisticated equipment but the conditions below ground keep changing.”

Keeping the lowered equipment stable enough for clear images at that depth, he said, is difficult.

While the depth itself is causing equipment instability — with a remote camera being lowered through 6-inch bore holes that narrow down to four inches inside steel pipes or casings in the ground — no land movement has been detected above, Chee said. Numerous monitors have been installed throughout the area to measure any signs of surface movement.

The steel pipes serve as the casings in the bore hole to stabilize and keep the hole open as equipment and cameras are sent below. The casings, Chee said, can move or become stuck due to the extreme depths.

In a separate delay, several days ago work was paused to take the district’s drilling machine in for repairs, Chee said. It is expected to be back onsite in the coming week.

But the timing on the completion of the camera drilling process, he said, is still unclear.

“We don’t have a specific time frame,” he said, adding that it would be “at least several weeks.”

Among the lingering questions is the condition of the tunnel boring machine that remains trapped about a mile ahead of the breach point, he said.

“We know there’s a significant amount of water down there, we continue to pump water out at a steady flow rate,” Chee said. But he said the water — likely groundwater from a subterranean aquifer — is not increasing.

The entire length of the tunnel from Carson to San Pedro — about seven miles — will be carefully inspected before work on the final leg of tunneling can resume. Cal/OSHA currently is reviewing plans for workers to be able to re-enter the tunnel at the northern three-mile-long section in Carson.

The section after that, Chee said, would be the next three miles heading south which would bring workers close to the breach site. But that only will happen once officials can determine more about what caused the breach, how extensive the damage is, and whether the tunnel is otherwise stable and safe for workers to re-enter.

Questions remain on whether other areas around or beyond the breach point may have been affected and that is what officials hope to determine with the underground camera images.

The camera inspection drilling above the breach site — which has taken place Monday through Friday — began in late September and was originally slated to last until at least the end of October. It has required one southbound traffic lane closure at times.

Work going forward, however, may also include some Saturday drilling work in order to expedite the task.

The breach occurred on July 9, temporarily trapping 31 workers. Collapsed material largely closed off the tunnel but workers, traveling through the tunnel on a tram, were able to climb over the top of the fallen sediment pile where there was still space. All were rescued with only a few minor injuries reported.

The ambitious, $630 million, multiyear Clearwater Tunneling Project launched in 2019 and was more than a decade in the works, requiring extensive planning with advance and ongoing community outreach. Work had progressed without problems until the collapse, which occurred about five to six miles from the only above-ground access point in Wilmington to the north.

Tunneling was not done under homes or other buildings but instead was done following only under streets. The project was on the last leg of its journey when the breach occurred.

The older, smaller underground wastewater pipes, meanwhile, remain in place and are still working, officials said.water