A working representation of contaminant sources, release mechanisms, migration pathways, exposure pathways, and receptors at a contaminated site. The CSM is the analytical backbone of site investigation, remedial design, and risk assessment, and is iteratively updated as new data arrive.
The Conceptual Site Model integrates geology, hydrogeology, contaminant chemistry, land use, and human and ecological receptors into a single representation, often a cross-section or block diagram, that shows how contamination got into the ground, where it is going, and who or what it could expose. ASTM E1689 and the Interstate Technology and Regulatory Council (ITRC) provide standard CSM frameworks.
A defensible CSM is the difference between a remediation that works and one that doesn't. It identifies data gaps that the investigation must close, drives remedy selection by mapping pathways and receptors against treatment options, and supports risk-based closure by documenting that all exposure pathways are incomplete or controlled. The CSM is a living document, refined as Phase II and Phase III data refine the source, transport, and exposure picture.
Also known as: CSM, conceptual site model.
The regulatory metric for thermal destruction performance, expressed as the percentage of a target contaminant destroyed across the system. Common permit thresholds range from 99.99 percent for general hazardous organics to 99.9999 percent (six nines) for PCBs, dioxins, and PFAS.
The duration that gas, vapor, or solids remain inside the heated zone of a thermal treatment unit; together with temperature and turbulence, one of the three governing parameters of complete contaminant destruction.
Liquid that has percolated through contaminated soil, waste, or stockpiles, dissolving and carrying contaminants downward to groundwater or to a collection system. The principal migration pathway for PFAS, dissolved metals, salts, and hydrocarbons from impacted sites.
Laboratory method that oxidizes PFAS precursors in a sample into measurable perfluoroalkyl acids, then quantifies the difference against a pre-oxidation baseline. Reveals the hidden precursor mass that targeted PFAS analysis alone misses.