MTA Deserves Applause for Caution in Tunneling

* Your editorial “Confidence in Subway Tunnel Is Sinking” (March 26) fails to recognize the care the Metropolitan Transportation Authority is exercising on two fronts: construction of an east-west Valley line and subway construction activities on Lankershim Boulevard.

In fact, The Times should be among the first to applaud the MTA for being fiscally responsible and concerned about safety.

The board of directors has approved construction of the Red Line only as far west as the San Diego Freeway. Only as far west, I should point out, as the MTA’s 20-year plan anticipates tax revenues and other funding will take it.

Realizing how important efficient rail transportation will be to commuters in the San Fernando Valley, however, the board has not ruled out the eventual extension of the line to Warner Center. That portion of the project is on the 20-year plan’s “B list” and can be reconsidered in the future with other rail projects now on hold.

As for construction of the subway beneath Lankershim Boulevard, it is true that the contractor--Obayashi Corp.--is proceeding slowly. The subsurface beneath Lankershim contains loose, sandy soils which are difficult to tunnel through and caution is prudent. As of this date, the contractor is slightly behind schedule, but the delay thus far has not affected the project completion date.

Hoping to avoid the ground settlement experienced on Hollywood Boulevard, the MTA’a contract with Obayashi requires the contractor to dig without loss of ground at the tunnel face. Accomplished properly, this will minimize, perhaps even eliminate, the possibility of creating voids in the earth above the tunnel and prevent resettlement at the surface.

The most recent settlement at Lankershim and Weddington Street indicated that the contractor has not yet developed the appropriate excavating techniques. When excavation stopped, Obayashi again consulted with tunneling experts about methods to avoid loss of ground at the tunnel face.

Tunneling beneath an urban area is a laborious and painstaking job. If disruptions at the surface are to be minimized, the contractor and the MTA must take the time to do the job correctly. Who wouldn’t agree with that?

JOHN J. ADAMS

MTA interim executive, construction

Los Angeles