Project Specifics

The site is an approximately 23-acre, undeveloped parcel in an area of office buildings, hotels, and the Brisbane Marina. Subsurface conditions include fill and refuse material, thick compressible clay deposits, and underlying alluvium and bedrock. The overall site development plan consists of the construction of five, three- to four-story buildings, a multilevel above-ground parking garage, surface parking, and miscellaneous site improvements, including pavements, landscaping, and utilities.

Geosyntec Scope of Services

Geosyntec’s scope of work to date has included:

• Synthesizing existing subsurface data;
• Performing deep borings to 300 feet and CPTs to 180 feet;
• Evaluating the depth to the existing clay cap;
• Performing site specific seismic response analysis;
• Estimating settlement around the site (upwards of 5 feet over 30 years);
• Evaluating the deep foundation system, consisting of H-piles in excess of 200 feet in length;
• Performing value engineering analyses to optimize the foundation and settlement design aspects;
• Developing and overseeing a pile testing program to optimize pile capacity; and
• Providing input and assistance to the design team.

Notable Accomplishments

At a site where there is potentially more steel below ground than above, optimization of pile capacity through the testing program has reduced the number of piles needed for axial capacity by maximizing the load associated with each pound of steel in the ground and produced a significant cost savings to our client. Geosyntec’s settlement estimates are being used by the design team to develop phasing and utility plans for the site that will allow for long-term operations while the site potentially settles over the design lifetime.

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