The CSM Framework: Pathways

The previous lesson established the Conceptual Site Model and its fundamental principle: risk exists only when source, pathway, and receptor connect. While identifying contamination sources and recognizing protected receptors forms the foundation of assessment, the pathway- the route by which contaminants migrate- determines whether potential risk becomes actual exposure.

A petroleum-contaminated soil source may lie only meters from a residential building, yet pose no immediate risk if contaminants remain immobile or physical barriers prevent exposure. Conversely, a relatively small contamination source can create widespread risk if pathways enable contaminants to migrate toward sensitive receptors like drinking water wells.

This lesson examines the pathways—the routes by which contaminants migrate from sources to receptors—and explains how pathway evaluation guides investigation priorities and remediation strategies in German contaminated site assessment.