Airport Liquefaction Susceptibility Analysis Report - ABAG ...

Fugro Consultants, Inc.
Project No. 04.79221200
6.2 Recommendations
6.2.1 Liquefaction Investigations
Liquefaction investigations are necessary for Buchanan and Livermore to more fully
characterize the potential aerial extent and amount of liquefaction-related deformation. Those
investigations should include a review of all available subsurface data, the collection of both
CPT and soil boring data and samples, geotechnical laboratory analyses that would include, at
a minimum, grain size analysis and Atterberg limits, aerial photographic analysis of site
development and fill placement history, and the construction of geologic cross sections across
the site showing the lateral extent and thickness of fill.
6.2.2 Additional Site Studies
Additional site studies are necessary at Moffett and Oakland to address the gaps in subsurface
data coverage across these properties. All available geotechnical and engineering geologic
reports for these airports should be obtained and reviewed to identify any data suitable for
liquefaction analysis and to identify areas with gaps in data coverage. Where significant
coverage gaps occur, a subsurface investigation should be developed in order to collect the
additional data.
A more comprehensive evaluation of fill thickness and character is recommended at Moffett,
Oakland, and San Francisco to address differential settlement potential and identify areas with a
higher susceptibility to liquefaction. This evaluation should include a review of all available
subsurface data, aerial photographic analysis of fill placement history, and the construction of
geologic cross sections across the site showing the lateral extent and thickness of both fill and,
specifically at Oakland, the Merritt Sand.
This evaluation should also include a review of all perimeter dikes and levees at San Francisco
and Oakland to assess the potential for slope stability and seepage that may result from
earthquake-induced liquefaction (it should be acknowledged that OAK is currently making
improvements to their dikes and levees to meet the FEMA recommendations and
requirements). The borings analyzed along the perimeter levees and dikes at Oakland do not
cover the first 80 feet and the last 30 feet of the alignment, resulting in the liquefaction
susceptibility of fill materials in these locations poorly constrained. In addition, evidence for
seepage was documented by URS (2011) along the Oakland levees and dikes between stations
168+00 and 188+00 and stations 193+00 to 220+00 that should be further evaluated.
6.2.3 Mitigation
Various methods have been used to mitigate liquefaction hazards within the San Francisco Bay
Area. Some of the most commonly used and effective techniques suggested by Martin and Lew
(1999) include:
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May 31, 2013