Gas Station: Stuart, Florida

Aerobic bioremediation with air sparging

Site Description

Underground storage tank (UST) leaks from a gas station contaminated shallow ground- water under the property. Following the removal of the leaking USTs and impacted soils around the tank cavity, combined air sparging and aerobic bioremediation was implemented to remediate the groundwater.

Site Characteristics

Geology and Hydrogeology
The setting of the site is a coastal beach complex dominated by sands and calcified deposits. The shallow subsurface including the perched groundwater zone was dominantly sand.

Ground Water Contamination

The size of groundwater plume that resulted from leaking USTs was estimated to be 8,500 square feet. The contamination was a wide range of petroleum constituents including benzene, ethylbenzene, toluene, xylenes, MTBE and naphthalene.

Results

Petrox aerobic bioremediation was implemented in conjunction with air sparging. The combined approach takes advantage of the stripping action of sparging to remove dissolved volatile contaminants and the availability of oxygen to support aerobic bioremediation. A total of 120 units of Petrox (1800 gallons) were injected into the contaminated ground water through vertical injection wells for three consecutive months.

After the Petrox inoculations, the contaminant concentrations were reduced across the property. The following table shows the overall contaminant reductions in three monitoring wells.