Environmental Site Assessment & Investigation Flashcards

What does the term 'conceptual site model' (CSM) represent in environmental investigation and remediation?

Answer: A systematic description of contaminant sources, release mechanisms, transport pathways, and potential receptors at a site

The CSM is a living document that synthesizes all known information about contamination sources, release history, transport pathways (soil, groundwater, vapor), exposure points, and potential receptors into a coherent site understanding that guides investigation and remediation decisions.

In direct push technology (DPT) soil sampling using a Geoprobe, what is the key advantage over conventional hollow-stem auger drilling?

Answer: DPT is faster, generates minimal waste, and reduces cross-contamination between vertical intervals

DPT advances small-diameter probes without drilling fluid or cuttings generation, enabling rapid collection of discrete soil and groundwater samples with minimal waste and reduced risk of cross-contaminating different depth intervals.

A potentiometric surface map is constructed from water level measurements in multiple monitoring wells. What does this map depict?

Answer: The hydraulic head distribution showing groundwater flow direction and gradient

A potentiometric surface map contours hydraulic head values across the site, showing groundwater flow direction (perpendicular to contour lines, from high to low head) and the hydraulic gradient driving that flow.

What is the significance of a 'data gap' identified during a Phase II investigation, and what action is typically required?

Answer: Data gaps represent areas of insufficient information that prevent completing the CSM or making a remediation decision, requiring additional investigation

Data gaps are identified when existing data are insufficient to characterize contamination extent, define the CSM, or support a remediation decision; they drive the design of additional investigation rounds or field activities.

Which type of geophysical survey is most commonly used to locate buried drums, underground storage tanks, and metallic debris at contaminated sites?

Answer: Electromagnetic (EM) Induction Survey

Electromagnetic induction surveys detect variations in soil conductivity and magnetic susceptibility caused by metallic objects, making them highly effective for locating buried drums, USTs, and metallic debris prior to intrusive investigation.

A site investigation reveals that contamination extends beneath an active building. What sampling approach is used to evaluate whether subsurface vapors are entering the building interior?

Answer: Sub-slab soil gas sampling and indoor air sampling as part of a vapor intrusion assessment

Vapor intrusion assessment involves collecting sub-slab soil gas samples immediately beneath the building foundation and indoor air samples to evaluate whether subsurface VOC vapors are migrating into the occupied building.