Ahtna Engineering Services, Inc. (Ahtna) performed additional characterization at the Gaffney Road East contaminated site in fall 2013 under contract to the Alaska Department of Environmental Conservation (ADEC). Contaminants of concern (COCs) include tetrachloroethene (PCE) and its degradation products trichloroethene (TCE), and cis- and trans-1,2-dichloroethene (cDCE and tDCE). The results of the fieldwork showed that PCE and/or TCE exceed ADEC groundwater cleanup levels (GCLs). We also determined vertical extents for the main plume area. PCE and/or TCE concentrations above GCLs extend from the top of the groundwater table to between 30 and 40 feet below ground surface (ft bgs) in the areas near the MW-32 and MW-34 well clusters.
To complete the work, we managed the installation of eight groundwater monitoring wells at various depths in six locations using a Geoprobe® 8040DT direct push rig while logging lithology. We filled field screening data gaps, obtained soil samples at the groundwater interface for chlorinated ethenes, and obtained geotechnical soil samples from the saturated zone. We also sampled 17 monitoring wells for chlorinated ethenes and geochemical parameters and 10 monitoring wells for carbon and chlorine Compound Specific Isotope Analysis (CSIA) for PCE, TCE, and cDCE. Ahtna analyzed sample for VOCs and monitored natural attenuation parameters using various EPA and ASTM approved methods.
Period of Performance