Geocon conducted a design-level geotechnical investigation for the design and development of a new Civic Center in Newark, California. At the time of our investigation, the site housed the previous civic center, which included a 7-story administration building and a library facility. These structures, along with various site improvements, were demolished to make way for the new civic center, which now includes a two-story city hall, a two-story library, new police building, and communications tower.
Our investigation revealed significant liquefaction-induced settlement potential—on the order of 3 ¾ inches. Geocon recommended the use of a ground improvement system in combination with remedial grading to mitigate the liquefaction hazard and improve bearing capacity and worked with the project team to develop plans for the use of vibratory stone columns (VSCs) beneath the three new buildings and the new communications tower.
Subsequently, Geocon was retained by the City for services during construction, which included reviewing Design-Build Entity (DBE) design documents and onsite construction oversight. We provided quality assurance observation and testing on behalf of the City during the construction of the VSCs and provided geotechnical testing and observation throughout the remedial grading. Geocon utilized CPT soundings after the installation of VSCs to quickly evaluate the efficacy of the ground improvement system at mitigating the liquefaction hazard; post-installation CPT data was analyzed and compared to pre-construction CPT data from our investigation and showed a reduction in liquefaction-induced settlement potential in accordance with the plans.
Geocon further coordinated closely with Alameda County Water District (ACWD) to coordinate inspections during the construction of the VSCs, as ACWD required grouting of many of the VSCs to protect groundwater but was not always available to be onsite. The VSCs provided significant cost savings compared to alternative ground improvement or deep foundation systems. Additionally, the CPT soundings conducted before and after installation provided accurate data on the system’s performance.
By recommending vibratory stone columns (VSCs) instead of more expensive deep foundation alternatives, Geocon saved the City significant costs.
Los Angeles, California
Irvine, California
Sacramento, California