For the plumes formed by a convex hull, the GeoTracker-provided monitoring well location was downloaded, which contains the latitude and longitude of each well. When interpreting groundwater monitoring reports, the multiple groundwater plume maps were layered into Google Earth as overlays, allowing the outer ring to be interpreted for the plume layer. Generally the estimating effort is performed by one of two methods: 1) interpreting the contour based on review of groundwater monitoring reports or 2) generating a polygon formed by the outer ring of the monitoring well network ( i.e., convex hull). The approach taken to apply this data has varied. Each plume map is assembled from public regulatory data associated with a given spill site. To estimate the groundwater plumes displayed in the Cleanup Deck, Terradex followed the method summarized here. The site-specific maps often do not show a plume boundary as an iso-concentration line – such as a 5 part per billion TCE – a delineation that would indicate an area likely for vapor intrusion. The maps multiply as the pattern repeats with each constituent of concern). These site-specific maps often segregate chemical constituents of concern (COCs) and impacted aquifers (e.g., one map for TCE in the A-level aquifer, one map for TCE in the B-level aquifer, and one map for TCE in the C-level aquifer. The site-specific groundwater maps are typically formed as a written deliverable from the potential responsible parties (PRPs) to the environmental regulatory agency that oversees incremental cleanup progress a map’s audience is an environmental professional, not the public. Plumes are typically studied site-by-site, and not in aggregate. Current groundwater plume maps, however, fail to clearly reveal the occurrence of groundwater plumes to key stakeholders – local government, contractors, and the general public. Knowing where groundwater plumes are located is basic to assessing the hazard posed when volatile organics vaporize from these plumes.
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