This project extended the Metro Gold Line subway from Union Station in downtown Los Angeles to East Los Angeles.The construction of the twin subway tunnels occurred through a very congested area of the city, as the entire alignment of this project was in a densely populated urban area.
First Street in East Los Angeles includes both residences and thriving businesses that required minimal disturbance. The team developed a comprehensive traffic management plan as well as maintaining the bus route by moving some of the stops. The team worked closely with the Los Angeles Department of Transportation to come up with the diversion plans, which resulted in minimal impacts to vehicular and bus traffic.
Each tunnel is 7,500 linear feet (lf) long. The tunnels were excavated with two new 21-foot-diameter earth pressure balance (EPB) tunnel machines in alluvial soils, both above and below the groundwater table. The precast segmental bolted and gasketed liner was furnished by Traylor/Shea/Ghazi Precast. Tunnel excavation was successfully completed in December of 2006. In addition to the main tunnels excavated and lined with the precast liner, four crosspassages and two sump structures were excavated using New Austrian Tunneling Method (NATM) techniques, and cast-in-place-lined between the tunnels. The precast liner limited infiltration to 10 gpm or less inflow of water over the entire length of the tunnels. The rail invert and pedestrian walkway concrete was also placed and finished by Traylor Frontier-Kemper.