The busiest and most congested freeway in the U.S., the “405” serves as a major north-south interstate in Southern California. To alleviate congestion, lanes are being widened, and a 10-mile, high-occupancy vehicle (HOV) lane is being added, along with support infrastructure such as ramps, bridges, and sound walls.
Serving as the lead geotechnical engineer, Kleinfelder had to conform to a compressed schedule and leverage company resources to meet the challenging construction deadlines and issues on this high-profile project, including: fifteen conflicts of the proposed construction on a Metropolitan Water District; 96-inch, high-pressure water feeder pipe; landslides on steep natural hill slopes, not represented in bid documents; logistical challenges involved with exploration and geologic mapping; and schedule for production of design documentation in a dynamic design environment.
Kleinfelder immediately mobilized 30 professionals from 12 offices. A geologic mapping, geophysical and subsurface investigation, and laboratory testing program supplemented data provided in bid documents. The exploration program addressed conditions at the sites of retaining walls, proposed cut slopes, and utility conflict areas. Despite several unanticipated geotechnical conditions, Kleinfelder developed engineered solutions for areas that had been impacted by landslides, for protection of utilities, and for required structure foundations.
The majority of the project components were optimized for lowest cost and ease of construction, with an aggressive completion schedule to avoid potential costly delays. Moreover, by optimizing earthwork and retaining wall design, Kleinfelder was able to significantly reduce construction costs.