Historical analytical data indicates the extent of dissolved BTEX and napthalene impact is relatively stable across the site with the highest concentrations noted at and in the area of monitoring well MW-8 (formerly MW-4) near the former tank pit.  Free product has never been encountered at the site.  Dissolved benzene at MW-8 is the only COC concentration that exceeds its GRP CAL at the site.  Monitoring well MW-8 contained a dissolved benzene concentration of 14.8 ppm (CAL = 0.465 ppm).

The consultant used existing COC concentration data to estimate the volume of contaminants requiring treatment.  In addition, consideration was also given to other oxidizable materials known or suspected to be present in the subsurface.  A site oxidant demand was then estimated using this information.  Based on the oxidant demand, an ozone injection system was selected capable of producing a sufficient mass of ozone per day such that site objectives could be achieved within a reasonable time frame.

The ozone sparge unit has been in operation for the last 6 months.  The most recent ground water analytical results show the reduction in Benzene concentration to be 83%, and the reduction in Total BTEX concentration to be 79% reduction.