Since 2004, this project has included pre-design investigation (PDI), treatability studies, remedial design (RD), and construction oversight services for the remediation of a site previously used for disposal of hazardous industrial wastes. One challenge faced was the presence of multiple, layered fluvial aquifers, coupled with the presence of recalcitrant 1,4-dioxane, which was not identified when the Record of Decision was prepared for this site. Other contaminants of concern (COCs) included hydrocarbons, volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), polychlorinated biphenyls, and metals.
A thermal treatability study was completed to evaluate the effectiveness of low temperature thermal desorption (LTTD) for remediation of VOC/SVOC contamination at various temperatures (450, 600, 750, and 900 degrees Fahrenheit). Based on the demonstrated success of LTTD in the treatability study and the results of the fugitive emissions study, an RD was prepared for implementation of the LTTD remedy.
To define the nature and extent of soil and groundwater contamination, EA conducted a PDI and has prepared and overseen implementation of RDs for multiple phases of remediation, including excavation and thermal treatment of 57,000 tons of soil, bioventing, and an in situ bioremediation injection program to treat residual low-level anaerobically degradable VOCs. As part of the ongoing phased remedy, options were evaluated for 1,4-dioxane remediation in soil and groundwater, factoring in its mobility and migration throughout the layered aquifers. This evaluation included collecting pre-design soil and groundwater data and performing a bench-scale treatability study.
EA designed an in situ chemical oxidation injection program to treat the 1,4-dioxane and other VOCs utilizing ferric-iron activated sodium persulfate. The program included injecting 200,000 pounds of sodium persulfate via 186 injection points. Post-injection monitoring to date has indicated favorable trends in the reduction of 1,4-dioxane and other VOCs. These remedies have been performed in conjunction with ongoing groundwater extraction and treatment, which will continue at the site until COC concentrations meet target goals to support monitored natural attenuation.