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CHMP: Site Investigation and Remediation

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Site Investigation and Remediation

Site Investigation and Remediation

This domain tests the cleanup pipeline: Phase I/II ESA, CERCLA PA/SI and HRS, RI/FS, ROD, remedial action, and O&M. It also tests matching a remedy to the source-pathway-receptor conceptual site model.

Core rules

  • Phase I ESA (ASTM E1527) is a records review, site reconnaissance, and interviews to identify recognized environmental conditions (RECs). It does not confirm contamination and is not a cleanup plan.
  • Phase II ESA confirms or delineates contamination with sampling. CERCLA: preliminary assessment/site inspection (PA/SI), hazard ranking system (HRS) scoring, NPL listing, remedial investigation/feasibility study (RI/FS), record of decision (ROD), remedial design/action, and operation and maintenance.
  • Build a conceptual site model: source, release mechanism, pathway, receptor, and exposure route. Remediation targets the risk-driving link.
  • Common remedies: excavation and disposal; soil vapor extraction (SVE); air sparging; pump-and-treat; permeable reactive barrier; in-situ chemical oxidation (ISCO); bioremediation; thermal treatment; stabilization/solidification; monitored natural attenuation (MNA).
  • NAPLs: LNAPL floats, DNAPL sinks. Pump-and-treat is often slow for DNAPL; source treatment plus plume management may be more realistic.

Worked example

A dry cleaner site has PCE in soil gas and a dissolved plume in groundwater, with a DNAPL source near the former dip tank. SVE is a good fit for the vadose-zone source; ISCO or excavation can treat the source zone; MNA or a permeable reactive barrier can manage the dilute plume. Choosing pump-and-treat alone would recover mass slowly and might not address the vapor pathway into nearby buildings-so also evaluate vapor intrusion.

Traps

Do not call a Phase I a “contamination report.” A Phase II is not a feasibility study. HRS scoring is not a risk assessment for a single receptor; it ranks sites for the NPL. Do not assume a dissolved plume has no source. MNA is not “do nothing”-it requires monitoring and contingency triggers.