BAI was contracted by the City of Santa Rosa to perform an integrated geotechnical investigation and environmental site assessment (ESA) for the proposed Lower Colgan Creek Restoration Project in Santa Rosa, California.  Lower Colgan Creek is part of the Agency’s flood control system. BAI’s geotechnical and environmental data will be used to develop specifications for a 6,523-linear foot stretch of channel that will be re-contoured by grading into a 7,281-linear foot, more natural, meandering configuration with a restored riparian habitat.

Based on the findings of the Phase I ESA, BAI designed a Phase II soil sampling and analytical testing program that provides soil chemical characterization for use by the future grading contractor.  BAI integrated the Phase II soil sampling with the geotechnical subsurface investigation that provided a value added service for the client.

BAI services for Lower Colgan Creek Restoration Project included document review and research, Phase I and Phase II ESAs, subsurface exploration and monitoring well installation, soil and groundwater sampling and laboratory testing, and engineering and geologic analyses, to provide conclusions and recommendations regarding:

• Embankment stability and gradient recommendations;
• Slope revetment/erosion protection alternatives;
• Site preparation and grading, including treatment of existing fill and expansive soils;
• Foundation support for the planned South Dutton Avenue extension vehicle bridge;
• The presence of contaminated soils and groundwater within the project footprint;
• Characterization of fill for landfills;
• Seismic ground motion values;
• Drainage and lateral earth pressures for retaining walls such as box culverts and arch culverts;
• Support for pavement sections;
• Construction considerations;
• Additional geotechnical services;
• Landfill approval for soil disposal.

BAI delivered a comprehensive report of findings that summarized the results of our reconnaissance and subsurface exploration from both the geotechnical and environmental standpoints.  This report will be used in the preparation of the construction specifications when the project goes out to bid.