Sunday, July 29, 2007
P87

Design and Cost Reduction of Remediation Technology Pilot Testing

Ann Keeley, Ground Water and Ecosystems Restoration Division, ORD, NRMRL, U.S. Environmental Protection Agency, 919 Kerr Research Drive, Ada, OK 74820

In order to effectively address the inherent variability of MTBE concentrations at a small fuel contamination site chosen for an in-situ in remedial technology test demonstration.  Curtain walls for metering mixtures of conservative and non-conservative tracers into an aquifer were used during a ground-water investigation of over 300 days.  The study was conducted to guide monitoring plan development for the bioremediation technology pilot test which would involve intermittent sparging of oxygen and propane into the test area.  Two experimental plots consisting of closely spaced tracer-injection and downgradient monitoring screens were used.  Two tracer experiments (bromide and bromide/d-MTBE) were conducted by injecting small volumes of high tracer concentration solutions into the injection wells and monitoring the tracer response at 72 downgradient sample screens located in the two 20 x 20 ft. (~6 m) plots.  The findings from 15 sampling events over a 10-month project period demonstrated that large variations occurred in short periods of time and over short distances (i.e. < 10m).  MTBE, d-MTBE, and bromide, which were purposefully or inadvertently introduced to the aquifer varied quite markedly in time and space.  Geochemical parameters on the other hand, which derive from water: aquifer matrix interactions, were found to demonstrate very low relative variability.  The tracer experiments led to substantial cost-savings in monitoring the performance of the remedial technology demonstration.


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