Bethel was contracted by the FAA to perform a feasibility study (FS) at six contaminated sites associated with fuel releases from former USTs that represent great challenges to remediate due to the depths and concentrations of contaminants, which equate to costly cleanups. FAA’s objective was to assess several remediation alternatives, given the site’s geological, hydrological, and climatological conditions, while considering their long-term operational costs for the station. A secondary objective was to conduct one groundwater and two vapor sampling events to comply with ADEC requirements. Bethel prepared and executed a work plan that described in detail groundwater and vapor sampling events. Groundwater sampling included low-flow sampling of 18 monitoring wells using both submersible and bladder style pumps. Vapor sampling involved installing three soil probes adjacent to an occupied residence and collecting vapor samples from the probes in addition to crawlspace and living space locations. The vapor sampling was conducted in late summer and early winter to determine if vapor intrusion (VI) was occurring and if seasonal effects influenced VI. Bethel was also tasked with modeling previously-collected site data with the ADEC Method 3 Hydrocarbon Risk Calculator (HRC) to determine if sites meet the state’s human health and ecological risk standards and, if not, what factors drove the risk. This crucial step of the project showed which contaminants must be targeted for future remediation and allowed Bethel to refine which technologies should be considered as remedial alternatives for the FS. The FS brought together the findings of the groundwater and VI sampling events, HRC evaluation, site-specific conditions, and considerations in overall costs to produce a recommended remedial alternative for the FAA.
Work performed
- Low-flow Groundwater Sampling
- Vapor Intrusion Investigation
- Hydrocarbon Risk Calculator Modelling
- Feasibility Study
