The success of the IRM promoted additional interest for expansion of the technology to other areas of the plume.  However, increases in concentrations of volatile organic compounds and polycyclic aromatic hydrocarbons in groundwater outside of the original plume boundary raised concerns that the oxygen injection may be inadvertently diverting the groundwater plume beyond the limits of the treatment zone.  A joint study was undertaken by KeySpan Corporation, the New York State Department of Environmental Conservation, and Suffolk County Department of Health Services to address these concerns.  The study included a review of existing physical groundwater parameter data and treatment system operational data; collection of continuous water level measurements over a fourteen day period in forty-eight monitoring wells; and the collection and chemical analysis of soil, groundwater, and soil vapor samples from the treatment zone.  Groundwater and soil vapor samples were collected over two periods, normal system operations and following a five day period when the system was taken out of operation.  A comparison of the data for each system condition, as well as a comparison to historic performance and monitoring data, is evaluated and presented.  The study concluded that the oxygen injection did not alter groundwater flow conditions in the vicinity of the injection wells.