This research project focused on sustainability issues in the southwest U.S. with an emphasis on water and energy. The efforts were directed through the UNLV Urban Sustainability Office with the funding used to develop a sustainability strategic plan; conduct extensive community outreach in the greater metropolitan area; provide seed money for multidisciplinary research teams to conduct studies in the areas of ecological, socio-cultural, and economic sustainability leading to community-based solutions; and to provide service-learning opportunities for UNLV graduate and undergraduate students. The research advanced understanding of urban and regional water issues with a particular focus on climate change and climate variability in the southwest. In addition, various events were held to promote discussion on energy, water, and sustainability discussions in the community. The impact of this research was broad dissemination of research through 13 peer-reviewed publications, learning opportunities for countless students as a result of class room equipment upgrades (see report for upgrade details), and new research funding for further advancement of these research efforts.

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Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants in the vadose zone. A diminishing rate of contaminant extraction over time is typically observed due to 1) diminishing contaminant mass, and/or 2) slow rates of removal for contamination in low-permeability zones. After a SVE system begins to show indications of diminishing contaminant removal rate, SVE performance needs to be evaluated to determine whether the system should be optimized, terminated, or transitioned to another technology to replace or augment SVE. This guidance specifically addresses the elements of this type of performance assessment. While not specifically presented, the approach and analyses in this guidance could also be applied at the onset of remediation selection for a site as a way to evaluate current or future impacts to groundwater from vadose zone contamination. The guidance presented here builds from existing guidance for SVE design, operation, optimization, and closure from the U.S. Environmental Protection Agency, U.S. Army Corps of Engineers, and the Air Force Center for Engineering and the Environment. The purpose of the material herein is to clarify and focus on the specific actions and decisions related to SVE optimization, transition, and/or closure.