Our team was tasked to design, install, and operate remedies for contaminated sites at the former Galena Forward Operating Location (FOL), a former United States Air Force installation at a remote location in Alaska. Many of the sites are contaminated with fuels, including JP-4 and Arctic diesel. A component of the remedies for several sites included sulfate-enhanced bioremediation. Remedy design and operational data are presented for a JP-4 site.
We designed a “green” approach using sulfate enhancements to address fuel contamination in portions of the aquifer that are saturated for most of the year (i.e., portions that could not be efficiently addressed by soil-vapor extraction [SVE] or bioventing). A slurry of agricultural-grade gypsum was injected into the residual non-aqueous phase liquid (NAPL) soil source zone. The gypsum dissolved over time, releasing sulfate to enhance biodegradation of fuel contaminants. The sulfate-enhanced bioremediation portion of the remedy requires no moving parts after injection and, more importantly, no electrical power. All electric power at Galena has be generated by fuel imported by barge.
The sulfate delivery system is operating as designed. Gypsum is being depleted slightly faster than anticipated, likely because groundwater flux is greater than estimated in the design. Sulfate is transported downgradient and appears to be utilized as anticipated. Fuel components in groundwater are trending toward cleanup goals.