MTA Resumes Tunneling Below Hollywood Freeway

The Metropolitan Transportation Authority resumed subway tunneling under the Hollywood Freeway on Monday after it agreed to repave a section of the busy roadway near Universal City that sank 3.79 inches.

To obtain Caltrans’ permission to resume digging under the freeway, the MTA also agreed to install an array of steel struts and concrete slabs in its tunnels and access shafts to prevent future settlement.

MTA project manager Charles Stark said he expected the extra work to cost less than $1 million and to take less than a month.

He said attorneys were investigating whether the cash-strapped transit authority would be able to ask tunneling contractor Traylor Bros.-Frontier Kemper to foot the bill. But he added that he was not unhappy with the Indiana-based firm’s excavation techniques.

“We can’t see anything that the contractor did wrong,” Stark said.

Caltrans ordered the MTA to halt tunneling last week after surveyors reported that the freeway had sunk a few tenths of an inch past the 3.5-inch limit in MTA’s permit.

Stark blamed the slump--which was 13 times deeper than forecast in an MTA report written before tunneling began--on the effects of drawing hundreds of thousands of gallons of water out of the San Fernando Valley’s loose, sandy soil prior to construction.

The “dewatering” technique caused soil 80 feet above the tunnel to consolidate. That left a long, shallow crater under the freeway, he said.

Stark said Caltrans engineers were concerned primarily that water would puddle in the center of the slump, causing fast-moving cars and trucks to lose control during storms. He said a Traylor Bros. paving subcontractor would begin to eliminate the depression in two weeks, working at night and on weekends.

After the paving is complete, he said, Caltrans would reset its settlement measurements at zero. It would then require another 3.5-inch subsidence to trigger further action.

When the two short, soft-dirt tunnels beneath the Hollywood Freeway are complete, Traylor Bros. will push two giant boring machines through them on rails.

At a spot just north of Cahuenga Boulevard, the machines will begin gnawing through Santa Monica Mountains bedrock to the site of a future Red Line subway station on Hollywood Boulevard.

Ground subsidence has plagued the MTA almost everywhere it has tunneled in Los Angeles. The transportation agency faces $2 billion in damages from lawsuits filed by property and business owners complaining of cracked floors and buckling walls along the tunneling route under Lankershim, Hollywood and Wilshire boulevards.