Subsurface Site Investigation

The purpose of a subsurface investigation is to collect samples and obtain actual quantitative measurements of chemical concentrations, hydraulic parameters, and lithological data within a particular hydrogeologic strata or group of strata. Environmental engineers can use these samples and measurements to assess the magnitude and extent of groundwater or soil contamination and support the selection and design of engineering options for remediation.

Engineers can conduct subsurface investigations using temporary groundwater and soil sampling techniques such as HydroPunch, soil probes, and cone penetrometers (Edge and Cordy 1989) or more permanent techniques such as the installation of monitoring wells and soil borings. Temporary techniques are less expensive but less reliable; therefore, they are usually used for screening purposes and the optimization of the location and number of permanent systems. Permanent techniques, on the other hand, are more expensive and more reliable; therefore, their use is usually limited to confirm actual concentrations and subsurface conditions.

Subsurface investigations involve several field activities such as drilling, installation, development, and sampling of monitoring wells. These activities are intrusive to the subsurface environment; therefore, engineers should conduct them with care to prevent cross-contamination and obtain representative groundwater and soil samples that retain both the physical and chemical properties of the subsurface environment. A description of these field activities follows.

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