Sonoma County

The Sonoma County Office comprises a team of dedicated Professional Geophysicists and Geologists. We specialize in offering a diverse range of proven geophysical technologies to support geologic, groundwater, environmental, and engineering investigations. Our findings play a pivotal role in the planning, designing, and constructing of critical infrastructure and facilities. Additionally, we assess environmental and archeological conditions and evaluate earth resources.

Our capabilities include state-of-the-art geophysical instrumentation and computer systems for in-field and office data analysis, word processing, and graphics. Founded in 1983, NORCAL Geophysical Consultants, Inc. joins Terracon, aiding their long-time clients with access to expanding geophysical service capabilities. Working with geologists, geotechnical engineers, hydrologists, environmental engineers, archeologists, land planners, government agencies, and property owners has given us vast experience, and we are ready and excited to partner with any client seeking these services. Contact us to find out how the strategic application of geophysics can be a crucial element in ensuring the success of your project!

GEOPHYSICAL

SURFACE GEOPHYSICAL METHODS

Surface geophysical methods can be used independently or integrated with other investigative methods such as test borings and other sampling programs for area investigations or site characterization. Surface geophysical methods can be used to:

• Determine soil and rock properties
• Investigate groundwater basins
• Map geologic structure and geologic hazards such as landslides and faults
• Delineate and characterize landfills and hazardous waste
• Locate buried tanks, utilities, and former excavations
• Determine zones of subsurface seepage

Subsurface geophysics methods the Sonoma team provides include:

• Electrical Resistivity Profiling
• Electromagnetic Terrain Conductivity
• Time Domain Electromagnetics
• Ground Penetrating Radar
• Magnetics
• MASW Shear Wave Velocity Determination
• Seismic Refraction
• Seismic Reflection
• Streaming Potential
• Utility Locating
• Vibration Monitoring

Read More

BOREHOLE METHODS

Borehole geophysical logging and imaging is used to characterize a variety of specific subsurface conditions. The equipment is very portable and can be easily shipped to distant or difficult to reach sites, including those that require helicopter access. Our latest computer software provides a wide range of data presentation formats and sophisticated 2-D and 3-D modeling capabilities.

• Caliper-determine borehole dimensions
• E-Log, Induction & Guard Resistivity-define stratigraphy and stratigraphic correlations
• Sonic-access casing cement bond; P-wave velocity correlations
• P & S wave Suspension Logger-determine compressional and shear wave velocities
• Optical and Acoustic Televiewer-delineate fracture patterns and orientations and other structural features
• Heat-Pulse Flowmeter-measure vertical groundwater flow
• Deviation-determine borehole verticality
• Temperature-Differential Temperature Fluid Conductivity-determine groundwater inflow and outflow depth locations
• Discrete Water Sampling-profiling of contaminate concentration levels
• Borehole and Water Well Inspection

Borehole methods the Sonoma team provides include:

• Acoustic Televiewer
• Acoustic Televiewer Analysis
• Optical Televiewer
• Optical Televiewer Analysis
• Fracture Analysis
• Stereo Analysis of Dips
• Digital Suspension P and S Wave
• Full Wave Form Sonic
• Electric and Natural Gamma
• Induction
• Log Presentation
• Vertical Groundwater Flow
• 3D Subsurface Modeling
• Color Borehole Video

Read More

GEOTECHNICAL

• Groundwater Basin Characterization
• Subsurface Conditions – depth to rock, thickness of overburden
• Geologic Hazards – faulting, landslides, karst topography
• Characterization of Lithology
• Borehole Logging – televiewer, P- & S-wave suspension

ENVIRONMENTAL

• General Site Characterization
• Thickness and Extent of Buried Landfill Debris
• The Location of Buried Tanks and 55 Gallon Drums
• Utility Detection and Routing
• Depth/Lateral Extent of Buried Contamination

FACILITIES

• Concrete Thickness
• Void Detection
• Rebar Placement
• Grade Beam/Footing Detection
• Archeological/Forensic Studies