A soils report (or geotechnical report) is a critical document for understanding the subsurface conditions of a construction site and ensuring safe, stable, and cost-effective development. When reviewing a soils report, it is essential to focus on specific elements to assess potential risks and ensure compliance with project requirements. Below is a guide to the key aspects to evaluate in a soils report:

• Soil Types and Composition:

• Look for a description of the soil layers (e.g., clay, sand, silt, gravel).

• Check for problematic soils such as expansive clays, loose sands, or soft organic material.

• Soil Classification:

• Verify the soil is classified using standard systems like the Unified Soil Classification System (USCS) or AASHTO Soil Classification.

• Groundwater Table:

• Note the depth of the water table and its potential impact on construction, such as drainage challenges or hydrostatic pressure on foundations.

• Soil Profiles or Cross-Sections:

• Review visual representations of subsurface layers for a clear understanding of the site’s geology.

• The bearing capacity indicates the load the soil can safely support.

• Ensure the report specifies the bearing capacity at the anticipated foundation depth.

• Compare the reported capacity to the design requirements of the structure to confirm compatibility.

• Immediate Settlement:

• This refers to soil compression occurring as soon as the load is applied.

• Long-Term Settlement:

• Evaluate potential settlement over time, especially in compressible soils like clay.

• Differential Settlement:

• Check for risks of uneven settlement, which can cause structural damage.

• Identify whether expansive clays are present, as these can swell when wet and shrink when dry, leading to foundation movement.

• If expansive soils are present, confirm the report includes mitigation measures such as soil stabilization or deep foundations.

• For sites in seismic zones, check if the report evaluates liquefaction risk, which occurs when loose, water-saturated soils lose strength during an earthquake.

• Ensure recommended measures (e.g., densification, deep foundations) are provided if liquefaction is a concern.

6. Drainage and Groundwater Recommendations

• Review recommendations for managing water, including:

• Site Grading: Proper slopes to divert water away from structures.

• Drainage Systems: French drains, sump pumps, or sub-drain systems to prevent water pooling or infiltration.

• Look for any concerns about high water tables or perched water, which can impact construction and long-term stability.

• Ensure the report provides clear recommendations for foundation types suitable for the site’s soil conditions, such as:

• Shallow foundations (e.g., slab-on-grade, strip footings).

• Deep foundations (e.g., piles, caissons) for unstable or weak soils.

• Specialized systems for expansive or liquefiable soils.

• Confirm foundation depths and dimensions align with the project requirements.

• For projects involving retaining walls, check the report’s assessment of lateral earth pressures, which dictate the structural design of the walls.

• Look for recommended values for active, passive, and at-rest pressures.

• If the site includes slopes or is located on a hillside, verify the report assesses slope stability to prevent landslides or erosion.

• Ensure recommendations for slope reinforcement, grading, or retaining structures are included if necessary.

• In areas prone to earthquakes, the report should evaluate:

• Seismic hazard classifications.

• Site-specific acceleration values.

• Ground response to seismic loads.

• Check for any additional seismic design recommendations.

• Look for instructions on how to prepare the site before construction, such as:

• Soil compaction standards (e.g., minimum compaction percentages for fill materials).

• Excavation depths and backfill requirements.

• Removal or replacement of unsuitable soils.

• Ensure recommendations align with local building codes and project specifications.

• Review data from field and laboratory tests, such as:

• Standard Penetration Test (SPT): Provides insight into soil density and strength.

• Cone Penetration Test (CPT): Indicates soil stratigraphy and load-bearing capacity.

• Atterberg Limits: For evaluating plasticity and shrink-swell potential of soils.

• Shear Strength Tests: For determining the soil’s ability to resist sliding forces.

• Look for any highlighted challenges or risks, such as:

• Difficult excavation conditions (e.g., dense soils, rock layers).

• Groundwater intrusion during excavation.

• Unstable soils requiring temporary shoring or dewatering.

• Verify whether the report identifies:

• Contaminated Soils: Presence of hazardous materials requiring remediation.

• Erosion Risks: For sites near water bodies or with exposed slopes.

• Ensure mitigation measures are provided if concerns are identified.

15. Compliance with Building Codes

• Ensure the report complies with local and state geotechnical requirements, such as the California Building Code (CBC) for projects in the Bay Area.

• Look for references to applicable standards (e.g., ASCE 7 for seismic design).

• At the end of the report, there is usually a summary of key recommendations. Verify this aligns with the project’s needs and design objectives.

A soils report is a vital document for assessing the safety and feasibility of construction projects. When reviewing a soils report, focus on the subsurface conditions, foundation recommendations, and risk mitigation strategies for seismic, settlement, and drainage issues. By carefully examining these key elements, you can ensure your project is built on a solid foundation—both literally and figuratively.