Geotechnical challenges for the Los Angeles to Pasadena Metro Gold Line Rail Transit Project

The Los Angeles to Pasadena Metro Gold Line Rail Transit Project provided many challenges with a variety of different geotechnical conditions along its alignment. The conditions include areas of deep existing fill soils at Union Station and the Yard and Shops area. Evaluations were made as to whether the existing fill could be used for support or whether the fill should be improved. The project includes a major crossing over the Los Angeles River where there were different soil and rock conditions at the two major pier locations. The project crosses a known active landslide area which required evaluation of stability and adequacy of mitigation measures. The project includes two areas of below grade construction in materials difficult to excavate; one of the areas was adjacent to an historic commercial district with many older unreinforced masonry buildings sensitive to ground movement. The project also had a crossing over the trace of an active earthquake fault.