CONTRACTS HAVE been signed for a $899M extension to the Los Angeles Metro Gold Line.
The $600M construction contract has been awarded to Eastside LRT Constructors, a joint venture of Washington Group International, Obayashi Corporation and Shimmick Construction Corporation.
The project will extend the light rail system 9.6km east from Union Station in downtown Los Angeles. It includes tunnelling as well as stations, elevated structures, bridge upgrading and a cut-and-cover section.
The tunnel has been fully designed by the client to save time and money, while remainder is design and build.
About 240m of cut-and-cover leads into the first underground station on the segment. 'The earth pressure balance tunnel boring machinery will be launched from here on its 2.9km twin-bore route heading east, ' explained LA Metro deputy project manager Eli Choueiry. The area is congested, passing under existing structures and utilities where compaction grouting will be used to avoid any damage, he said.
The twin tunnels will be about 6.7m in diameter, running mainly through alluvium with an escarpment section prone to deep underground movement. The tunnel is designed to accommodate seismic events, added Choueiry.
The precast concrete-lined tunnels will be done in a single pass with bolted, gasketed joints said Choueiry. Half the tunnel alignment is above the groundwater table and half below. Double-gasket lining is used throughout to provide water tight joints.