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Site Investigation Techniques (3 steps)

The site investigation process involves several stages to gather crucial information about the location where a structure is planned to be built. It starts with a Preliminary Investigation involving heavy fact-finding. During this stage, the project team seeks to understand the type of structure to be constructed, its intended use, and local building codes. The geotechnical engineer plays a vital role at this point, as they can take specific actions to optimize the investigation process and conserve time and resources.

To begin the site investigation, the geotechnical engineer conducts a thorough review of existing data, aiming to reduce the need for extensive original research. Some of the valuable sources for geological data include:

  • Survey maps: These maps provide important information about the topography, boundaries, and characteristics of the site.
  • County soil maps from the USDA: These soil maps offer insights into the soil types, composition, and potential geotechnical challenges in the area.
  • USDOT soil manuals: Publications by the United States Department of Transportation that offer valuable information about soils and their engineering properties.
  • Well logs: Records of previous drilling and borehole investigations in the vicinity, which can provide essential data about the subsurface conditions.
  • Other existing reports or permitting documents: Previous studies, reports, and permits related to the site can contain valuable data on geological conditions, environmental considerations, and any past geotechnical assessments.

By leveraging these existing data sources, the geotechnical engineer can build a foundation of knowledge and focus subsequent investigations on areas where critical information is lacking. This approach saves time, resources, and allows for a more efficient and targeted site investigation.

As the site investigation progresses, the geotechnical engineer will then move on to performing field investigations, which may involve drilling boreholes, conducting soil and rock sampling, and performing laboratory tests to characterize the subsurface conditions thoroughly. The collected data will be analyzed, and engineering recommendations will be provided to support the design and construction of the planned structure while considering geotechnical and environmental factors.

Detailed Investigation

During the site investigation phase for construction projects, it is essential to collect samples from the intended site. One crucial technique for this purpose is to create test borings, which involve drilling into the ground to obtain samples of both disturbed and undisturbed soil. These samples are then analyzed and observed to gather important information about the site.

To start the process, a general guideline is to drill one exploration hole in each corner of the proposed structure and one in the center. This initial sampling strategy provides an initial understanding of the site’s soil composition and characteristics. Additional borings may be required based on the consistency and uniformity of the results obtained from the initial samples. These additional borings allow for a more comprehensive assessment and facilitate further testing.

The depth of the borings is crucial and should be sufficient to collect samples from below the unsuitable topsoil layer, reaching deeper into more stable soil layers. The depth of the borings should accommodate the intended structure and its design requirements, including anticipated building loads. This ensures that the collected soil samples represent the conditions that will directly influence the construction process and the overall stability of the structure.

By following these procedures and collecting appropriate soil samples, construction professionals can gather valuable data to inform the design and construction processes, ensuring that the project is built on a solid foundation.

Supplementary Investigation and Construction Recommendations

In the last stage of the process, there is a focus on analyzing and planning based on the findings obtained from earlier stages. The collected rock, soil, and water samples play a crucial role in assessing potential risks. By examining the chemical makeup of the groundwater, any harmful impacts can be identified, and appropriate measures can be planned to address the issue. Furthermore, this phase involves preparing for potential natural events such as earthquakes, groundswells, floods, shrinkage, permafrost, or erosion. Through careful planning, strategies can be developed to mitigate the potential effects of these phenomena.


When it comes to seeking top-notch expertise, look no further than Cigano Engineering LLC for valuable guidance. Our company boasts extensive worldwide experience and is committed to offering unparalleled insights and solutions to address your inquiries. Whether you have lingering uncertainties about construction site investigation techniques or the overall process, we invite you to reach out to us for an engaging discussion regarding your upcoming project.