Use Of Scaps Suite Of Tools To Rapidly Delineate A Large Mtbe Plume

The Navy Site Characterization and Analysis Penetrometer System (SCAPS) was used to<br>rapidly delineate the extent of a dissolved Methyl Tertiary Butyl Ether (MTBE) plume<br>resulting from an underground storage tank system petroleum release. Records indicated<br>that approximately 11,000 gallons (42 cubic meters) of leaded and unleaded gasoline<br>were released from the tank system between September 1984 and March 1985. MTBE<br>was identified in the most downgradient monitoring wells present at the site in the Fall of<br>1996. These wells were beyond the extent of the delineated benzene plume, but<br>contained MTBE levels exceeding 10 parts per million (ppm). A combination of<br>innovative water sampling, rapid turn around chemical analyses, near real-time plume<br>mapping, and geophysical methods were used to delineate the extent of the MTBE plume<br>to 35 parts per billion (ppb) concentration levels, install longitudinal and sentry wells in<br>the most appropriate locations, and conduct the site characterization efforts in an<br>expedient fashion. During the 15 field days it was determined that the dissolved MTBE<br>plume extends approximately 4,100 feet (1,250 meters) in length, approximately 500 feet<br>(150 meters) in width through the widest segment, and approximately 33 acres (133,55 1<br>m”) in map view. Assuming that contaminants were first introduced into the aquifer in<br>September 1984, the calculated linear contaminant velocity for dissolved MTBE at the<br>downgradient edge of the plume is approximately 342 feet (104 meters) per year for this<br>site.