VOC Source Identification


Soil contamination is very heterogeneous, which is to say that contamination is highly variable over short distances. Consequently, contaminated soil can be suspected for years or decades on the basis of contamination in groundwater, while the exact source of the problem remains unknown. Locating soil contamination is challenging when the source is beneath a building floor, and more for multiple sources over a large area. At an operating Midwestern manufacturing facility various contaminants, primarily the chlorinated compounds trichloroethene (TCE), and dichloroethene (DCE), were present in groundwater. On the basis of site history, The State EPA and previous consultants had identified fourteen areas, such as drum storage areas and solvent degreasers, as likely sources of the contamination but more than a decade of soil and groundwater sampling failed to locate the problem.


Cox-Colvin proposed locating the source via soil gas, and in just two weeks, collected 248 samples in a 40-foot grid configuration. Samples were collected at a depth of five feet via Geoprobe, placed in small glass vials, and analyzed onsite by a mobile laboratory. The soil-gas “hot spots” bore little resemblance to suspected sources, but subsequent soil sampling found high-level soil contamination at the hot spots. Cox-Colvin remediated the contaminated soil in the following months, and succeeded in cleaning up groundwater.