Objective

While variable across the federal, state, and local levels, guidance for assessing the groundwater to indoor air pathway at chlorinated solvent-impacted groundwater plume sites is evolving toward multiple-lines-of-evidence-based approaches that involve indoor air, subslab soil gas, deeper soil gas, groundwater, and soil sampling in combination with screening-level modeling. The basic data requirements for pathway assessment have been increasing with time, and the data interpretation and decision making are becoming more conservative and complex. This reflects experiences with conflicting lines-of-evidence at sites, low confidence in the ability to correctly interpret the data, and a limited peer-reviewed knowledge base to rely upon.

The overall objective of this project is to conduct integrated field-scale (FS), lab-scale (LS), and modeling studies (MS) focused on the following six topics critical to the evolution towards more confident and cost-effective pathway assessment guidance: (1) temporal variability of indoor air concentrations (FS); (2) relationship between groundwater concentrations and indoor air impacts (FS and LS); (3) changes with time in vapor emissions from, and soil gas profiles above, chlorinated solvent-impacted groundwater plumes (FS and LS); (4) spatial and temporal variability in subslab and near-foundation soil gas concentrations (FS and MS anchored to existing data sets); (5) investigation of alternate assessment approaches (FS and LS); and (6) indoor chemical sources (literature and FS). An existing home known to have vapor intrusion impacts will be used for the FS studies.