Geohazards

Geohazards are natural or human-induced geological conditions that pose risks to people, infrastructure, and the environment. They include events such as landslides, rockfalls, debris flows, earthquakes, ground subsidence, sinkholes, and soil instability, all of which can lead to significant damage and disruption if not properly identified and mitigated. Understanding geohazards is a critical component of site evaluation, design, and long-term land management, particularly in areas with challenging terrain or variable soil and rock conditions. Through careful investigation, monitoring, and engineering solutions, geohazard risks can be assessed and managed to protect public safety and ensure the stability and resilience of constructed and natural systems.

Landslides & Slope Stabilization

EA has extensive experience in ground stabilization, including projects involving landslides, debris flows, post-fire debris flows, rockfalls, creep movement, erosion control, and bank stabilization. EA provides comprehensive services from forensic investigation and litigation support to design, monitoring, and construction oversight of mitigation systems for all types of slope failures. EA personnel are highly experienced in slope failure investigations, utilizing surface and subsurface methods such as geologic mapping, drilling and instrumentation installation, test pits, hydrophobic layer identification, and geophysics to delineate and analyze failures. Their analytical capabilities include slope stability, infiltration, seepage, unsaturated flow, and hydraulic modeling, as well as structural analyses to determine causes, predict future movement, and design repair solutions. EA’s technical staff have completed design, specifications, and construction drawings for a wide range of retaining wall systems, including mechanically stabilized earth (MSE), tieback, soil nail, sheet pile, secant, anchored, gabion basket, Hilfiker, gravity, and cantilever walls. These stabilization systems have incorporated horizontal drains, underdrains, French drains, and riprap, with construction oversight to ensure quality control.

Expansive, Collapsible And Settlement Prone Soils

With expansive, settlement-prone, and hydrocollapsible soils and bedrock prevalent across much of the western U.S., EA has developed advanced expertise in evaluating and designing for these challenging conditions. Our work in this area has contributed to numerous publications and significantly advanced both the state-of-the-art and state-of-the-practice in predicting and mitigating heave and collapse/settlement potential. EA has extensive experience providing civil and geotechnical design services for residential and commercial developments with problematic soils including site characterization with geotechnical investigations, instrumentation installation and monitoring, laboratory testing, and geotechnical analyses. The problematic soils site characterization aids in the design of foundations, retaining walls, pavement, and site grading and drainage. EA’s team is highly experienced in remediation design for residential and commercial foundations, analysis and design of foundation underpinning, compaction grouting, and excavation and fill replacement. EA personnel have also completed analysis and design for both shallow and deep foundation systems. Recognizing the complexities of foundation design on expansive soils, EA co-authored Foundation Engineering for Expansive Soils (Nelson et al., 2015), the most up-to-date reference on the subject.

Wildfire Assessment & Design

EA provides specialized wildfire assessment and design services to help property owners and communities recover from the devastating effects of fire and post-fire flooding. Our comprehensive investigations combine on-site evaluations, detailed mapping, and high-quality photography to accurately document fire-related impacts. We also work closely with property owners to understand site-specific conditions and challenges, ensuring our recommendations are tailored to each unique situation. From identifying necessary repairs to preparing detailed cost estimates for remediation, EA delivers practical, science-based solutions to restore safety, stability, and long-term resilience to fire-impacted areas.

Flood Mapping & River Restoration

EA provides comprehensive inundation mapping services to help clients assess flooding risk and support public safety. Combining expertise in hydrology, hydraulics, and GIS mapping, EA produces accurate and easy-to-understand inundation maps that illustrate floodplain boundaries, spatial extents, and depths at various water-level intervals. These maps are critical tools for emergency responders, enabling rapid evacuation planning downstream of dams and other hydraulic structures. EA utilizes advanced hydraulic modeling software, such as HEC-RAS and FLO-2D, integrated with ArcGIS to create detailed floodplain models tailored to specific project needs. Our inundation mapping services include FEMA permitting, hazard classification of dams, instream hydraulic structure and spillway design, river restoration mapping, and development of Emergency Action Plans (EAPs). Through these efforts, EA delivers high-quality flood determination products that play a vital role in risk mitigation and public safety planning.

Geohazard Services:

Engineering & Design

  • Site Characterization
  • Landslide Investigation
  • Problematic Soils Identification
  • Hydrocollapsible Soils
  • Settlement and Compaction
  • Geologic analyses, geologic hazards
  • Slope Stability Modeling
  • Infiltration/Seepage Modeling
  • Heave/Settlement Calculations
  • HEC-RAS and FLO-2D Modeling
  • Slope Stabilization Design
  • Foundation Design
  • Post-Wildfire Assessment and Design
  • Inundation Analysis and Mapping
  • Construction Oversight and Testing

Environmental Monitoring & Compliance

  • Permitting, compliance
  • Stormwater management
  • Remedial investigations and site characterization
  • Groundwater remediation
  • Feasibility studies
  • Stormwater management
  • Health & safety

Construction Material Testing

  • Field engineering
  • Soil, concrete, asphalt testing
  • Quality assurance/quality control
  • Geotechnical laboratory testing

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