570-Megawatt Otay Mesa Energy Center
Otay Mesa, San Diego County, California

Hushmand Associates, Inc. (HAI) performed two (2) geotechnical investigations to provide recommendations for earthwork and foundation design and site-specific seismic design criteria for the proposed 513-megawatt (MW) baseload capacity (608-MW with peaking) natural gas-fired, combined cycle Otay Mesa Energy Center (OMEC), located nearly 1,600 feet north and 700 feet east of the intersection of Otay Mesa Road and Alta Road, and southeast of Johnston Canyon, near the international border in the southeast portion of San Diego County, California.

The proposed OMEC, that comprises an approximately 46-acre parcel, includes installation of two combustion turbine generators, two heat recovery steam generators with combined 157-foot-high smokestacks, one steam turbine generator, air-cooled condensers, administration/warehouse/maintenance building, a water treatment building, power distribution centers, piperacks, underground sumps and utilities, transformers, a fire pump house, water storage tanks, roads, parking areas, and other miscellaneous equipment and structures.

A probabilistic seismic hazard analysis (PSHA) was performed to estimate the design ground motions at the site. Our geotechnical investigation addressed Geologic and Seismic Hazards such as fault rupture, ground shaking and seismicity, liquefaction potential, earthquake-induced settlements, lateral spreading, and static and differential settlements of a large number of major foundations to support massive equipment with large static and dynamic loads using state of the art approaches. HAI provided general earthwork recommendations for site grading, stability analysis for safe deep excavations, and designed large diameter cast-in-drilled shafts (i.e., 12-foot diameter, 40-foot deep caissons) for installation of new transmission line structures. HAI is currently providing earthfill special inspection services during final grading activities, foundation construction and caissons drilling activities.