Soil vapor extraction (SVE) has been used since 1992 to remove carbon tetrachloride from the vadose zone within the 200-PW-1 Operable Unit at the Hanford Site in Washington State. The primary sources of the carbon tetrachloride are waste sites that were used for disposal of waste liquids from process operations. The purpose of SVE operations at these waste sites is to mitigate the threat of carbon tetrachloride vapors migrating through the soil column and contaminating the underlying groundwater. Freestone, in conjunction with PNNL, performed a study to determine whether adequate information had been compiled to affirmatively answer end point guidance questions and support a decision to terminate the SVE operations.
Freestone produced internal and decisional drafts of the “Status and Path Forward Report for the 200-PW-1 Operable Unit Soil Vapor Extraction System” document to resolve these issues. The document provided the regulatory and technical justification for the closure of the SVE system within the 200-PW-1 OU. The USEPA accepted the recommendations of the decisional draft, authorizing the permanent shut down of the SVE system and transition to an on-going confirmational montoring program.