Project Specifics

Between 2005 and 2011 Geosyntec provided engineering services for a major petrochemical client and other project shareholders in the siting, geohazard assessment, targeted ground improvement, and foundation evaluation for a proposed on-shore liquefied natural gas (LNG) processing and marine terminal facility on the western coast of Africa. Our role on behalf of the overall project operator included feasibility assessments for site foundations and, during construction, provision of geotechnical assurance reviews during dredging and filling operations to improve site conditions during foundation construction.

Geosyntec Scope of Services

Geosyntec received multiple assignments related to three major facets of the project:

• Ground Improvement. Our team conducted a feasibility assessment of targeted ground engineering improvements to identify foundation alternatives to driven piles including deep dynamic compaction, vibrocompaction, wick drains and surcharging, and deep soil mixing (DSM). Our recommendation of DSM was incorporated into the front end engineering design (FEED) package and resulted in bid costs for foundations substantially less than estimates for driven pile foundations.
• Filling and Settlement. This project included a 7-million-cubic meter dredging and land reclamation operation. Geosyntec developed an integrated site settlement-sand fill model to predict site settlement and sand fill volume needs during construction and future facility operations. Our predictions were used to direct filling elevations and to provide schedule information, allowing the earliest demobilization of dredging equipment.
• Foundation Performance. The foundation system included more than 12,000 overlapping, 25-meter DSM columns to provide deep foundation support. Our review of EPC contractor quality control records identified a significant number of as-built DSM columns that had evidence of unmixed zones. We developed 2D and 3D soil-structure interaction finite element analyses of the DSM columns to evaluate performance of the as-built columns and developed a geotechnical assurance recommendation for our client.

Notable Accomplishments

Geosyntec worked with the client and other stakeholders to provide geotechnical assurance reviews from financial investment decision to facility mechanical completion. In particular, our analyses established fitness- for-purpose of the DSM-supported foundations in the absence of sufficient EPC design documentation. Our work allowed stakeholders to become confident in the performance of the foundations at this LNG facility.

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