Rapid Full Scale Remediation of MTBE in Groundwater Joleen Kealey Robert Roth, Ph.D., PE Joseph Pezzullo, PE                 A gasoline spill from former underground storage tanks (USTs) resulted in petroleum hydrocarbon and Methyl Tertiary Butyl Ether (MTBE) impact to soils and groundwater at a gasoline station in Concord, Massachusetts.  Site assessment information showed MTBE concentrations in groundwater of up to 3,400 ug/l and other hydrocarbon contaminants including benzene (114n ug/l), toluene (268 ug/l), ethylbenzene (448 ug/l), and xylenes (1,749 ug/l).  Terra Vac conducted an OxyVac bench test upon which the full-scale field application was designed.  Field operations commenced on July 2000, consisting of several hydrogen peroxide (H2O2) injection points and a network of soil vapor extraction (SVE) wells to extract off gasses from the in-situ oxidation.  Groundwater sampling for contaminant concentrations, Fe+2 consumption, and pH as well as off gas monitoring were conducted at routine intervals throughout the course of the project.  As of December 2000, six injections of H2O2 were completed, and groundwater monitoring revealed that only one monitoring well remained above the clean-up criteria of 70 ug/l MTBE.  All the other gasoline constituents had been reduced to less than 5 ug/l.