Indoor Air Contamination from a Shallow GroundWater VOC Plume – Experience with the GrantsChlorinated Solvents Plume Superfund Site, CibolaCounty, New Mexico

摘要

The Grants Chlorinated Solvents Plume site is an area of volatile organic compoundrn(VOC)-contaminated ground water. U.S. Environmental Protection Agency Region 6rn(USEPA) initiated a Remedial Investigation/Feasibility Study (RI/FS) at the Site in 2002.rnChlorinated solvents have been detected in shallow ground water (from 4 to 6 feet belowrnground surface) at the site. Tetrachloroethene (PCE), trichloroethene (TCE),rncis1,2 dichloroethene (cis-1,2-DCE) trans-1,2 dichloroethene (trans-1,2-DCE),rn1,1 dichloroethene (1,1-DCE), and vinyl chloride have been detected in concentrationsrnover 50 parts per million in the shallow aquifer. As part of the RI/FS, USEPA evaluatedrnthe vapor intrusion pathway. Ground water, soil gas, indoor and ambient air samplingrnwas conducted in and around six residences above the ground water plume plus twornselected background locations to determine if the ground water contamination wasrnimpacting indoor air. This paper presents the monitoring results along with thernattenuation factors calculated from those results.rnThree rounds of indoor and outdoor air samples and one round of soil gas andrngroundwater samples were collected from the residences and surrounding areas. Indoor air samples were analyzed using selective ion monitoring and achieved detection limits inrnthe low parts per trillion range. Results ranged from non-detect to 179 micrograms perrncubic meter (μg/m3). Soil gas concentrations ranged from non-detect to 95,000 μg/m3.rnThese data were then used to determine the relation between groundwater, soil gas, andrnindoor air contaminant levels.rnThe soil vapor results generally corresponded with the known dimensions of thernchlorinated solvent plume in ground water. The relative trends in ground water and soilrngas concentrations may provide information that is useful for selecting soil gas data forrncalculating attenuation factors.