VERTEX conducted a Remedial Investigation/Feasibility Study (RI/FS) at the Site in 2018 – 2019 under a Pollution Liability Insurance Agency (PLIA) grant. The purpose of the RI was to characterize the extent of soil and groundwater contamination identified in a 2017 environmental site assessment. The RI characterized soil, groundwater, and soil vapor. The Site’s contaminants of concern (COCs) included gasoline range petroleum hydrocarbons (GRO), benzene, toluene, ethylbenzene, and xylenes (BTEX), and naphthalenes.
The Site was enrolled in the Technical Assistance Program (TAP), PLIA’s voluntary cleanup program. Following its review of the RI/FS, PLIA issued an opinion letter on January 6, 2020, that noted 1) a cleanup action of soil and groundwater was necessary to achieve regulatory compliance, and 2) the downgradient extent of the groundwater contaminant plume was not defined towards the west-southwest in the City of Kelso’s right-of-way (ROW). VERTEX subsequently completed a supplemental soil, soil gas, and groundwater investigation in the winter of 2022. Based on this data,
VERTEX evaluated remedial options and selected in-situ chemical oxidation (ISCO) and plume stabilization reagents to clean up soil and groundwater contamination at the site. VERTEX implemented the in-situ cleanup as an interim action on behalf of the Client that included baseline groundwater sampling, oversight of four (4) injection events, and performance groundwater sampling after the final ISCO treatment. VERTEX prepared an interim action report that provided a narrative description of the cleanup, and soil and groundwater data. In addition, the interim action report included an evaluation of the performance monitoring data and recommendations for future actions. The interim action report documented that the in-situ cleanup action significantly reduced contaminant concentrations in soil and succeeded in meeting groundwater cleanup criteria.