Evaluation of a Soil Vapor Extraction System: A Post-Audit Assessment

by Ira May,
Zhenhua Jiang,
Lisa Durham,

Document Type: Proceeding Paper

Part of: WRPMD'99: Preparing for the 21st Century


(No paper) Numerous sites contaminated with volatile organic compounds (VOC) have implemented soil vapor extraction (SVE) systems to remediate the unsaturated zone. The SVE systems have the advantage of leaving the soils and infrastructures in place during the cleanup process resulting in large cost savings. Typically, field implementations of SVE systems have often proceeded without the benefit of extensive numerical modeling to provide for an optimum engineering design and to estimate the time required to reach the target cleanup levels. Modeling would also be helpful in the understanding of the interactions between soil cleanups and ground water contamination levels. The U.S. Army Environmental Center (AEC) has been conducting characterization and cleanup activities at the Twin Cities Army Ammunition Plant (TCAAP),New Brighton, Minnesota, to remediate contaminated soils, sediments, and groundwater with VOCs. These remediation efforts include SVE systems at two sites on the installation that remove VOC from soils and effectively reduce contaminant migration to groundwater. These SVE systems have been in operation since 1986. Sampling results have indicated removal of large volumes of VOCs during this period and recently significant decrease in the removal rates. The objective of this study is to use site-specific data collected at TCAAP to develop a multi-dimensional unsaturated numerical model for a post audit analysis of the SVE systems. The model is used to assess the efficiency of the remediation systems, the effect of these systems on the ground water, and to evaluate alternative designs to determine possible system improvements. As part of the study, sensitivity and importance analysis were conducted to identify the critical input parameters required to simulate the SVE process. This paper presents preliminary results of the study. Ultimately, the results of this study are intended to be used to bridge the gap between using empirical correlations and field experience for system design and using numerical modeling for evaluating system performance and design, and to help stakeholders to formulate reasonable goals in the soil and ground water environments.

Subject Headings: Soil pollution | Groundwater pollution | Soil gas | Unsaturated soils | Numerical models | Volatile organic compounds | Mitigation and remediation | Soil water | Minnesota | United States

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