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TGI has performed an extensive investigation and assessment of subsurface methane gas at a 2,500-acre residential development in the City of San Diego.  The objectives of this study were to characterize the extent, magnitude and distribution of methane and other fixed gasses in the subsurface, to assess the source of the methane gas and to evaluate public health and safety issues associated with the presence of methane. 


The investigation included installation and field monitoring of more than 500 multi-stage gas probes.  Field monitoring proceeded during various phases of work over a period of several years and included monitoring of fixed gas concentrations (methane, oxygen, carbon dioxide), atmospheric and subsurface pressures, and other pertinent information.  The project involved management and evaluation of a database containing more than 5,000 data sets with tens of thousands of readings.  TGI prepared a series of reports that included both area-wide reports as well as hundreds of individual property reports, with database management used to extract and parse data for specific locations.


Results of the assessment were used to assess risks associated with the subsurface methane evaluate if and where gas mitigation measures were required for homes, public buildings and other facilities including underground dry utilities (electric distribution and telecommunications systems) to comply with County and SDG&E standards and requirements.  

Subsurface Methane Assessment

Santaluz Master Planned Community, San Diego, CA

Client:  Santaluz, LLC/Taylor Woodrow

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