SOIL OXIDANT BLENDING: BROWNFIELD SITE
OPELIKA, AL

The site covers 4.4 acres and contains a 950,000 sf warehouse building constructed in 1958. Soil contamination from a former paint solvent bulk storage farm (SWMU#32) was identified on the NE corner of the site. Contamination included LNAPL and non-halogenated VOCs (namely toluene, naphthalene, ethylbenzene, xylenes, and trimethylbenzenes) resulting from solvent releases via distribution piping at the former tank farm.

Subsurface investigation indicated the presence of weathered saprolite(sandy-silt to silty-sand) overlying metamorphic gneiss schist bedrock at 60-80ft-bgs. The groundwater table was measured at 6-20ft-bgs.

Total contaminant concentrations were in excess of 2,000mg/kg. Due to the small quantity of impacted soils exceeding target treatment goals, soil excavation and off-site disposal at a Subtitle D land fill was originally recommended. ADEM subsequently classified the soils as “hazardous,” thus requiring disposal at a Subtitle C land fill at a cost of >$250 per ton.

An alternative treatment was designed using a solution of catalyzed hydrogen peroxide combined with sodium persulfate to treat soils in-place with considerable cost savings

In-situ soil blending of approximately 350 tons of soil was performed over a 2-week period using a specialized soil blending apparatus that attached to a conventional-sized excavator. Work was completed in August 2011

Field test kits were utilized during blending to track progress. Confirmatory soil samples indicated total VOC concentrations were below the risk target treatment goals which resulted in an NFA. (see graph)