Ongoing drill work on Western Avenue, just south of where Weymouth Avenue intersects in San Pedro, will require extended hours beginning Tuesday, Feb. 17, in the continuing effort to gather more information about what caused a breach while tunneling work was going on to install new, larger wastewater pipes.
Longer hours will be set from 7 a.m. to 5 p.m. Monday to Friday, and work is expected to continue through March. The traffic control hours will also be extended — from 6 a.m. to 6 p.m. Monday to Friday — to accommodate the new phase of the work.
The project being conducted by the Los Angeles County Sanitation Districts requires contractors to drill four more bore holes to capture images of an open space under the street that spans the underground tunnel breach site.
The work is needed to finish installing “a system of sonar devices that will be lowered underground to produce a clear 3D image of the area at depth (approximately 320 feet below street level),” according to a Thursday, Feb. 12, news release.
The imaging, the release said, “will allow contractors to determine the best way to fill the space above where the tunnel breach occurred. Drilling has been difficult due to underground conditions and limited working hours.”
The extended hours, the notice said, “will allow drilling, sonar mapping and, if needed, slurry pumping to fill this space quicker and more efficiently.”
The effort will use two separate drilling rigs previously deployed, the release said, and employ the same traffic control during the newly extended hours.
“This is anticipated to help this work achieve its objectives more efficiently,” the notice said.
The California Department of Transportation approved the extended hours and work.
Following a first-hand inspection earlier this year of the initial portion of the underground tunnel for the Clearwater wastewater pipe project, conditions in the 3-mile space ahead of the breach area appear to be stable, according to a Feb. 5 update from the Los Angeles County Sanitation Districts.
“The inspection along the completed tunnel indicates it is stable and intact,” the report said. “As a result, Cal/OSHA has authorized a second phase of re-entry to allow inspection of the tunnel to within 150 feet of the breach area so the investigation and engineering assessment for repair and recovery can take place.”
Drilling activity on Western Avenue, near Fifth Street, meanwhile, “remains ongoing to assess the conditions above the breach at approximately 350 feet below street level,” the report said.
The investigation has remotely identified an empty space about 10 feet by 20 feet in size, located about 310 feet below ground level at the breach site, according to the report.
In-person inspections received the go-ahead in December and teams have since gone about three miles in from the entrance adjacent to the A.K. Warren Water Resource Facility on South Figueroa Street, north of Lomita Boulevard, to restore ventilation, establish power and inspect the tunnel’s structural integrity.
Information and updates about the project can be found at clearwater.lacsd.org.