Evergreen conducts continual groundwater sampling at the facility, not just as part of the RIRs. Sampling is necessary before, during and after remediation is complete; therefore, sampling will continue at this facility for quite some time. The current work under evaluation (what’s included in the RIRs) includes defining the nature and extent of contamination in the subsurface as well as significant information on the geology and hydrogeology, which do not require additional aquifer analysis to review. Remaining aquifer analysis, which is the fate and transport model, takes the RIR data and predicts migration. The eventual Final Report for the site will also include additional analysis to demonstrate that remediation goals have been attained, which will include further groundwater analysis of aquifer conditions.
The direction and rates of groundwater flow are evaluated frequently at the site and groundwater samples collected routinely from various hydrogeologic units beneath the facility. The Remedial Investigation activities also evaluated the areas where the confining layers in the subsurface were not continuous through the completion of soil borings, installation of monitoring wells, collection of groundwater samples, groundwater elevations and completion of aquifer tests to determine hydraulic properties of the groundwater units. These data will be used for the upcoming evaluation of contaminant movement in the fate and transport evaluation through the use of a 3-dimensional numerical model which will be presented in the Fate and Transport Remedial Investigation Report.
Characterization of the refinery geology, hydrogeology, and extent of contamination, including study of the pathways that could exist, has been ongoing and is included in the RIRs. A fate and transport analysis will be prepared once all the RIRs have been approved, and the analysis will include model simulations of contaminant transport. This report is expected to be submitted by the end of 2021.