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Limited-Access Bioremediation in a Factory Setting

A factory in New Hampshire had a volatile organic compound (VOC) release detected in a storm-water outfall pipe. Hydrogen Release Compound (HRC) injection was determined to be the best remedial solution. Tight soils, shallow water table, access limitations, and pending property sale complicated remediation. Groundwater was directly below the floor slab. The plume was centered on the storm-water drain which carries runoff from the upgradient parking lot under the building. The VOCs are believed to have entered the subsurface in the central area of the building through spillage; the storm drain system was a preferential pathway. The groundwater contamination was addressed through bioremediation using HRC. Application required many injection points and applications, due to the low permeability of the soil. Due to interference with operations and property sale, repeated openings of the floor for injections using a drill rig were not feasible. Permanent injection points were installed, but would not be accessible for direct injection. Therefore, a trench was cut into the concrete floor slab between each point and the wall. Piping ran from the injection point to the wall, terminating at a standpipe with a quick-connect fitting. Each trench was then fillled with concrete to restore the floor slab. Since starting HRC treatment, VOC levels at the outfall have dropped to below the state regulatory standard. One well had levels of 1800 ug/L and 1200 ug/L of Cis-1,2 Dichloroethene and Vinyl Chloride in April, 2008. By January, 2009, both were below MCLs. Site closure is expected to be completed in a reasonable timeframe. The treatment has not interfered with Site activities or with sale of the Site.