Following a release from a refined product pipeline, rapid assessment of impacted soil and groundwater was completed using a combination of hydro punch and mobile gas chromatography (GC) lab. Once adequately assessed, impacted soil was remediated primarily by mass removal. Residual soil that remained was treated with a combination of InSitu Chemical Oxidation (ISCO) and enhanced bioremediation, leading to reductions below protective concentration levels (PCLs) and regulatory closure for soil issue. However, concentrations of up to 8.55 mg/L of benzene remained in groundwater.

A bench-scale treatability test indicated that alkaline-activated sodium persulfate could achieve significant reduction of contaminant mass in groundwater. A pilot test for ISCO application with recirculation (“push-pull”) was successfully completed in a representative area.

Full-scale ISCO application targeting three impacted areas was completed with a network of 31 injection and 13 extraction wells. Post full-scale ISCO for the site resulted in significant reductions in TPH-gasoline and benzene in source area. Natural attenuation via natural source zone depletion (NSZD) and/or enhanced biostimulation/bioaugmentation is planned at the site to address the dissolved phased concentrations that still exceed regulatory levels.

Primary Author / Conference Presenter:
Arun Neupane
Senior Scientist
Terracon Consultants, Inc.
Houston, Texas, USA

Edward W. James, P.G, Terracon Consultants, Houston, TX
Dan Schneider, P.E., Terracon Consultants, Houston, TX