This paper is a case study of the implementation and operation of an active permeable barrier-trench system beneath an oilfield service facility in eastern New Mexico. The system was designed to prevent the migration of petroleum hydrocarbon contaminants into the groundwater. Gasoline-range contaminants were discovered during the removal of underground fuel storage tanks at the site.

The active permeable barrier trench system was installed in 1992 and consists of two trenches, which are 128 and 132 ft long and approximately 15 ft deep. Trenches extend approximately 3 ft below the surface of the water table and were installed in three phases. Each trench was lined with a water-permeable geotextile fabric barrier, which was used to keep silt from permeating into the trench, but still allowed water to freely flow through the fabric. Each trench was then filled with 8 vertical feet of 2-in. gravel to increase porosity and permeability within the furrow. The remaining 6 ft of trench was filled with soil and the entire area was capped with asphalt.

Each trench was fitted with an air transmission system, at a depth of 14 ft below grade, to bubble air into the passing groundwater. Air was supplied by a blower at the surface to strip volatile contaminants from the water column and increase the dissolved oxygen content of the groundwater to promote microbial activity. Nutrient feed pipes were set in the trenches at a depth of 12 ft below grade. The feed pipes were used to inject nutrients into the groundwater to promote microbial growth and increase hydrocarbon degradation. Vapor extraction lines were installed at a depth of 8 ft below grade to remove any volatilized hydrocarbons. The vapor extraction system was connected to a passive ventilation system at the surface. The system has been in operation for approximately 2 years with good results.

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