Development of a Landfill in Difficult Site Conditions at the Port of Los Angeles

In order to accommodate the increase in container trade and vessel sizes, the Port of Los Angeles (POLA) has embarked on a port-wide container wharf upgrade program and channel deepening program. To meet the demand for additional backlands to the upgraded wharves, POLA is developing landfills using dredged materials from the channel deepening program placed within containment dikes. Approximately 17-ha (43-acres) of land are being developed in two stages within the Southwest Slip of the West Basin area. About 765,000 cubic meters (1 million cubic yards) of harbor bottom material dredged during channel deepening were identified as contaminated and unsuitable for open ocean disposal. The second stage of the landfill (west fill) was also used as a disposal facility for the contaminant material. The design and construction of the landfill posed unique geotechnical challenges as the site contains varying thickness [8-12 m (25–40 ft)] of soft and highly compressible foundation material beneath the approximately 10-17 m (30–55 ft) thick dredged fill materials, which are also composed of predominantly fine-grained compressible materials. The difficult soft site conditions and demanding project schedule required the need for a significant amount of wick drains installed over water as well as on land, and surcharge placement to improve the site with the time constraint. Land-based wick drains in excess of 3,500,000 m (11 million ft) and water-based wick drains of more than 700,000 m (2.3 million ft) were used in the project, making it the highest usage of wick drains in a single project in Northern America. The containment dikes were required to be designed to meet defined seismic performance criteria under operating level earthquake (OLE) and contingency level earthquake (CLE) conditions. This paper provides details of subsurface conditions, design, monitoring and ground improvement evaluation of the landfill.