EPA Region 6 requested the SAB conduct a review of the Region's Geographic Information System Screening Tool (GISST). The GISST is an environmental assessment tool developed to provide a systematic approach to considering single media and cumulative impacts in making decisions concerning complex projects, such as those subject to the National Environmental Policy Act (NEPA). The GISST uses geographic information system coverages and environmental and socioeconomic data to provide screening level assessments of the potential environmental vulnerabilities of project locations or the impacts of specified activities. Decision criteria are used in the GISST to score available data on a scale of one to five, where one equals lower potential environmental vulnerability or concern and five equals a higher level of vulnerability or concern. Scores are used by decision-makers to help prioritize potential project locations and alternatives and to help identify levels of environmental concern. EPA Region 6 asked SAB advice on the validity of the GISST methodology, the defensibility of the GISST results, and the usefulness of the GISST, particularly within the NEPA process. EPA Region 6 is also interested in making the GISST more user-friendly, and is seeking comments on further enhancements to the GISST.