Lower Colgan Creek Restoration Project – Santa Rosa

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.

Sonoma Marin Area Rail Transit (SMART) Project Planned Station…

As part of the Stacy Witbeck/Herzog team, BAI performed geotechnical investigations and geologic hazard evaluations along the length (approximately 41 miles) of the Initial Operating System One (IOS-1).  This stretch included investigations for bridge abutments at 10 bridge replacements, new track, and dozens of grade crossings.

Our work consisted of researching available pertinent reports and existing data for all 14 station sites and 10 bridge sites, conducting subsurface geotechnical investigations at station locations, replacement bridge sites, and at over 100 key locations throughout the rail alignment.  Our investigations targeted geotechnical factors that may influence design and construction of fills, bridges, and station elements.  Project challenges included developing efficient, effective approaches for addressing weak, compressible or expansive surface soils, liquefaction potential in response to earthquake shaking, settlement of bay mud under fill, pile driving through bay mud into hard Franciscan rock, and shallow groundwater.

Specific challenges included the following:

  • Weak deposits, such as young bay mud, are prone to compression and settlement when loaded, and consequently are not suitable for support of fills or structural foundations.
  • Potentially expansive surface soils that underlie much of the SMART alignment in Sonoma County.
  • Groundwater at depths less than 10 feet deep, and the associated potential for caving; necessity for dewatering of excavations extending below these depths.
  • Seismic considerations, including the effects of earthquake shaking on foundations, embankments and retaining walls, and the loss of shear strength and potential soil volume reduction in loose, saturated sandy/silty soils below the groundwater table via liquefaction.
  • BAI provided construction observations and testing including pipe pile installations and cut and fill slopes and retaining structures.

Novato Bus Facility

Golden Gate Bridge Highway and Transportation District – Novato Bus Facility site – groundwater characterization and hydrogeologic assessment

As the prime consultant, BAI performed environmental and geotechnical investigations at the Golden Gate Bridge Highway and Transportation District – Novato Bus Facility. The Novato Bus facility is located at the north end of Novato adjacent to the Highway 101 right of way. BAI performed an environmental and geotechnical investigation for remedial design to remove residual petroleum hydrocarbon contamination. This investigation included a geotechnical study for design parameters for a large soil excavation, sheet pile support walls, dewatering characteristics and foundation support.  Additionally, BAI manages multiple subcontractors including drillers, civil engineers, structural engineers, surveyors, utility locators and many others. BAI provides direct communication and project coordination with the Golden Gate project lead engineer.

Project aspects include:

  • Researching available pertinent reports and existing data for the site;
  • Project planning and coordination including timelines, gantt charts, budgeting for a public agency and public record documentation;
  • Continual monitoring of site conditions, both above ground and subsurface;
  • Prepare survey drawings of the site including topographical, boundary, utilities and drainage;
  • Conducting subsurface geotechnical, environmental and hydrological investigations including drilling by direct push, hydropunch, hollow-stem auger and CPT borings.
  • Preparing detailed construction drawings and assisting the district with preparing bid packets for construction.
  • Assisting with all permitting and reporting requirements with local and state agencies including project coordination with Caltrans.

Municipal Well Impact Assessment Report – Santa Rosa

Municipal Well Impact Assessment Report for sites 2410 Montgomery Drive and 2310 Midway Drive, Santa Rosa, CA

  • BAI was tasked with characterizing the impact on the regional aquifer of historical releases of DNAPLS from two dry cleaner sites located in Montgomery Village. The study focused on the impact from pumping City Wells along Farmers Lane on a migration of constituents of concern (COC) in the shallow most aquifer.
  • BAI designed nested wells at several locations to simultaneously monitor groundwater elevations in 3 separate water bearing zones. Site hydrology comprised of alluvial deposits behaves as a series of semi-confined aquifers.  Both vertical and lateral migration of COC’s were continuous monitored over several years.  Groundwater draw down due to pumping from the city wells was monitored in each water bearing zone continuously over time using transducers with self-contained data loggers in each nested well screen interval. Data was downloaded monthly from the transfers providing continuous characterizations of groundwater movement.

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