On Saturday June 17, 2006 Joe Buley F. ASCE and Life Member, arranged for a tour, by a group of Life Members, of the East Los Angeles Extension of the MTA’s Gold Line including the 1.7 mile double tunnel under construction. The group consisted of Ted McConville, Larry Lewis, Joe Buley and Garvin Pederson also guests Rich Montefort , John Filler, Warren Heer and Rich Haller LA Section President.
The tour began at MTA’s construction offices near Soto Street and Cesar Chavez Avenue. where we were given an extensive safety orientation by MTA’s safety engineer Javier Lora Although they have not experienced any problems with toxic gases, MTA outfitted everyone with emergency breathing devices. We were also informed the tunneling machines have several toxic gas sensing devices.
Decked out in hard hats and other safety equipment we first looked at the proposed “flyover” a bridge over the freeway interchange near Union Station. We then followed the alignment through “Little Tokyo District” to the tunnel portal near “Mariachi Plaza” in Boyle Heights. At this point we walked down stairs, some 60-feet below the street surface, to the point where the rail cars for the tunnel boring machines (TBM’s) unload their excavated material and pick up the concrete tunnel segments. We then proceeded approximately 800 feet along the tracks in Tunnel No. 1 to the TBM.
These huge TBM’s made by Zosen in Germany are boring 21-feet diameter tunnels. These machines which not only excavate the material but, they also place the precast concrete tunnel segments and then grout behind the segments. The machines are computer controlled onsite by an operator and all information is transmitted to the engineering offices above ground. The concrete segments once in place behind the TBM’s shield are bolted together. When the entire circumference of a 5-foot tunnel section is completed the TBM moves the shield forward with hydraulic jacks. Other than machine operators and maintenance personnel there is little or no manual work in the tunneling operation. At the present time they indicated they were progressing approximately 50-feet every day and hope to reach their goal of 100-feet a day. As a matter of interest the concrete segments are fabricated in Lancaster and transported to the site. Everyone was very impressed with the efficiency and safety of the tunneling operation.
Upon completion of the tunnel inspection we followed the alignment to the Gold Line terminus at Atlantic Blvd. and 3rd St.. in East Los Angeles. Along the alignment we also observed the surface grouting operation that precedes the tunnel excavation to prevent settlement of existing structures on or near the project alignment.
All of us thank MTA ( Joe Buley, Fred Smith and Javier Lora) for a most interesting tour of this well needed addition to the transportation system in Southern California.
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