MTA Begins Excavation on 2nd Subway Tunnel

Excavation on the western tunnel of twin subway passages beneath North Hollywood began Monday, using modified equipment to prevent a repeat of the sinkage problems that have plagued the idled eastern side of the massive transit project.

The Metropolitan Transportation Authority said workers gingerly scooped out a small amount of earth with the new equipment, opting to move forward cautiously in loose, sandy soil prone to shifting and sliding.

“It’s just the very beginning,” MTA spokesman Steve Chesser said. “We want to see how this works before we dig down and install similar [equipment] modifications on the other machine” excavating the eastern tunnel.

Work on the eastern side was halted in April after just two months when workers detected an additional half-inch subsidence beneath Lankershim Boulevard, following an earlier subsidence of about five inches in March. The MTA and the contractor on the $65.4-million project have since been hashing out how best to continue without risking more sinkage.

The transit agency determined that the problems could be corrected by modifying the tunneling equipment--high-tech machinery worth hundreds of thousands of dollars. Among other refinements, MTA officials directed the contractor, Obayashi Corp. of South San Francisco, to lengthen the hood covering the scooping machine to shore up the soil ahead of the tunnel face.

The MTA also directed workers to adjust the breasting table, which catches soil shaken loose from above the tunnel, and to increase the power of jacks that push the digger forward through rocks and boulders.

Chesser said the MTA would gauge the effectiveness of the adjustments in the newly started western tunnel before making the same modifications to equipment on the eastern portion, which had progressed 216 feet before operations were shut down. Ultimately, the twin Metro Red Line tunnels are to stretch two miles from North Hollywood to Universal City, hooking up to tunnels that connect the San Fernando Valley to Downtown Los Angeles.

Work on the project has been held up for weeks because of ground sinkage and tardy delivery and assembly of tons of equipment. Tunneling was to begin on the western tunnel four to six weeks after excavation started on the eastern half in February, but the subsidence problems forced a delay until Monday.

The tunneling is to be completed in 1997. MTA officials say that despite the delay in tunneling, they expect the project to open as planned in the year 2000.