Horizontal air sparging utilized as a site control measure

A horizontal air sparging system (HASS) was installed in 1996 as an interim measure (IM) at a former firefighter training area on Cape Canaveral Air Station, Florida. Waste fuels and solvents were burned on-site in an unlined pit for 20 years. Site geology is characterized by homogeneous sandy beach deposits and a shallow groundwater table. A thin layer of non-aqueous phase liquid and fuel saturated soil act as a continuing source of a groundwater plume which discharges to downgradient surface waters. The IM goal is to reduce and eliminate the discharge of vinyl chloride dissolved in shallow groundwater to the nearby sensitive surface waters, hence reducing risks associated with exposure to human and ecological receptors. The HASS is 354 m long and consists of six overlapping segments installed using horizontal trenching techniques to a depth of 7.5 to 9 m. Critical design aspects of the HASS include: trench sparge flow and stripping efficiency; air compressor flow rates; pipe deflection to offset pressure loss; and modeling ambient air concentrations. The design minimizes uneven air flow distribution across each leg, resulting in preferential flow paths vertically through the trenched area maximizing groundwater mixing and volatilization.