Vapor Extraction of Volatile Organic Compounds from Clay Soil: A Long‐Term Field Pilot Study

Abstract

Abstract A vapor‐extraction method was evaluated for remediation of clay soil contaminated by a paint thinner, consisting of a mixture of volatile aromatic hydrocarbons. Natural clays have low permeability to liquid or gas flow, and remediation by in situ methods is usually considered inappropriate. However, successful vapor flow through the clay was predicted on the basis of laboratory studies showing increased clay porosity and fracturing in the presence of organic solvents. A vapor extraction pilot study was conducted in a test area containing an estimated 1780 kg of paint thinner. The site was instrumented with vapor extraction wells and numerous soil vapor and pressure monitoring wells to delineate the zone of reduced pressure and sample the soil gases within the test site. Monitoring for eight months indicated that the contaminated clay was permeable to air and vapor flow with an effective range of influence extending 20 ft from the vapor extraction well and that 19% of the initial paint thinner was removed.