Development of permeable barriers for groundwater remediation: Air stripping of methyl tertiary-butyl ether (MTBE)

Physical barriers constructed in a contaminated groundwater system that intercept and degrade or remove soluble pollutants yet allow groundwater to flow through are called permeable barriers. They may be constructed as trenches placed down gradient from a leak or spill, and the trench backfilled with media which intercepts the solutes and removes them from solution. This project investigated the feasibility of using trench based air stripping to remove volatile hydrocarbons from groundwater contaminated with gasoline components, specifically methyl tertiary-butyl ether (MTBE). Based on theoretical calculations and previous laboratory research a 9 m long trench-based air stripping/biodegradation barrier was constructed at a site contaminated from a leaking underground gasoline storage tank. Monitoring data show the trench removed approximately 100% of the MTBE reaching it by natural groundwater flow, even at a relatively low air-to-liquid flow ratio. The total construction cost of the barrier was less than $5000, including the installation of a monitoring well, and annual operating costs were found to be about $180/year. Guidelines for succesful application of the permeable barrier concept to groundwater remediation are presented based on the experience from this project.