As-Needed Public Works Geotechnical Services

San Francisco, CA


San Francisco Public Works and San Francisco Public Utilities Commission

In addition to our large projects, TERRA has significant experience in providing geotechnical and construction services to local agencies such as San Francisco Public Works (SFDPW) and San Francisco Public Utilities Commission (SFPUC). TERRA is in a Joint Venture with ENGEO, Inc. in providing geotechnical services for SFDPW and in a joint venture with ARUP, Inc. in providing geotechnical services for SFPUC.

These projects range from small percolation and limited geotechnical exploration, to complete geotechnical design reports and construction inspection. Below are several projects we have completed:

1580 Burke Avenue SFMTA Facility Improvements The 103,000 sq. ft warehouse owned and operated by SFMTA is being redesigned and retrofitted to provide a new facility for SFDPW and SFMTA emergency vehicles and to provide increased storage capacity for their warehouse operations. This building was constructed in the 1960s over land reclaimed from San Francisco Bay by filling, and is supported on spread footing shallow foundation with a slab on grade. The building has experienced uneven settlement of at least 6 inches due to existing loads and poor subsurface.

TERRA performed field inspection and logging of geotechnical mud rotary borings and cone penetrometer test probes as part of the geotechnical exploration supporting the design. TERRA then assisted with preparing a Geotechnical Report that included the results of the subsurface investigation, evaluation of liquefaction and settlement potential, seismic hazards, and foundation design recommendations to improving the existing site which included micropiles and lightweight fill. The project is now in construction-phase and TERRA provided special inspection services to observe and document the micropile installation as part of the site improvements.

San Andreas Pipeline No. 2 Replacement The SAPL2 pipeline was constructed in early 1900s using iron lock-bar pipe. A 10 mile segment of SAPL2 located in San Bruno, CA is slated to be excavated and replaced in sections and slip-lined in other sections where open-trench excavation is not feasible. TERRA performed field inspection and logging of geotechnical borings as part of the design report. TERRA also performed slope-stability analyses along steep segments of the pipeline and prepared grading, compaction, and shoring recommendations. The project is currently in construction bidding-phase.

San Andreas Reservoir Landslide Repair and Erosion Assessment San Andreas reservoir is a 19,000 earth dam that is a major part of SFPUC’s penisula watershed and water supply system that as a result of work at Calaveras Dam has operated at higher reservoir levels than it historically has. This has lead to erosion of the shoreline that impact east and west service roads that follow the shore. In addition, recent high precipitation storms have caused landslides to impact segments of the east service road. TERRA prepared several reports documenting the erosion and developed recommendations to mitigate further erosion. These include rip-rap design, shoring walls, drainage, and grading to repair and reduce future landslide and erosion impacts to the service road.

Castro Mission Health Center Seismic Retrofits This building, owned and operated by SF Department of Public Health, provides primary care to residents with emphasis on low-income and vulnerable populations. The existing building, built in 1964, is a two-story concrete-framed structure which is supported on buried shallow concrete footings with grade-beams; and a ground floor slab constructed as a slab-on-grade. The building currently has deficiencies under modern seismic code and structural retrofits are currently being designed to upgrade it in-place using new concrete shearwalls installed on the outside of the structure.

TERRA performed a complete geotechnical exploration that included mud rotary borings, laboratory testing, cone penetrometer probes, and developed a Geotechnical Report that documented the results of the geotechnical exploration and summarized the subsurface conditions. This report also provided foundation recommendations such as allowable bearing capacity, sliding resistance parameters, and lateral earth pressures. TERRA worked closely with the City’s structural engineer, Biggs Cardosa & Associates, to develop lateral bracing recommendations for the shear walls that allowed the use of eccentrically loaded footings to support the concrete shearwalls and thereby minimize shoring and underpinning requirements.

Clarendon Ave Auxiliary Water Supply System SFPUC has been working to improve its emergency water supply system that would allow them to divert and provide water in the event of an seismic event that could rupture main water supply lines. Located at the base of Sutro Tower, several planned improvements are to be constructed at Clarendon Ave. TERRA Engineers performed a geotechnical exploration which included several borings and prepared a design report which included excavation, compaction, and shoring recommendations to support the project.

San Francisco Panhandle Playground Percolation and Geotechnical Exploration A small playground located in the panhandle of San Francisco is slated to receive major upgrades. As support of this work, TERRA performed several double-ring infiltration tests and auger borings in the playground which was summarized in Geotechnical Data Report

Washington Square Park Percolation and Geotechnical Exploration One of the oldest parks in San Francisco is located at Washington Square in North Beach district of San Francisco. The park is plagued with poor drainage issues as it’s situated over a historic stream channel that was filled in with clayey deposits. TERRA engineers prepared a Geotechnical Data Report which included several double ring infiltration tests and direct-push drilling and sampling which will support the design of future drainage improvements.

San Francisco International Airport (SFO) Consolidated Administration Campus Building A new administration building was constructed in 2018 at San Francisco International Airport and founded on over 150 reinforced-concrete auger cast piles. TERRA Engineers provided special inspection services during construction to observe and document the installation of every auger cast pile.