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C7041e31 Teclutus Inc Page 4 Pre-Bench Test Rpt George's Service Project No 425 2 March 10,2005 ' 5.0 BENCH SCALE TEST STUDY REPORT ' Dr Angus McGrath of SECOR International Inc is a Geochemist, and he wrote the evaluation report (Attached in Appendix A) for metal analysis in lieu of bench scale study for ozone sparging based on the groundwater and soil results (Table 1, Table la, and Table 2) ' and his experience and knowledge with the sirrular projects Following is the summary of the findings in the discussion of results in the report (by ' SECOR International Inc - Appendix A) • The groundwater samples in Table 1 were acidified before filtering, and the acidification likely resulted in the dissolution of some suspended solids in the samples These results are not representative of dissolved metal concentrations with the exception of hexavalent chromium which was observed to be below the limits of detection even though total chromium was observed ' • The groundwater samples were collected (February S, 2005) from MW-1 and MW- 101 and analyzed for the CAM-17 metals (see table la) These results (Table la) do not have any concentration artifacts as a result of suspended solids Table 1 a indicates that metals and trace elements in the dissolved conditions are below the detection limits except barium, chromium, and molybdenum (only MW-1) Barium and molybdenum concentrations are significantly small 1 • Presence of total chromium in all the groundwater samples indicates that total chromium is likely in the groundwater at concentrations below the 50 pg/L (MCL) The reason of the presence of total chromium in the groundwater at the given pH is ' not clear • Table 2 is the summary of soil samples from various depths None of the detected metals and trace elements is above regulatory limits SECOR International Inc uses the threshold concentrations of 50 mg/Kg to evaluate whether a site has the potential to generate hexavalent chromium during the application of potassium permanganate (much greater ability than ozone to generate hexavalent chromium in the groundwater) Total Chromium concentrations are below this threshold of 50 mg/Kg • Trace levels of total chromium are present in filtered groundwater samples (Table I a) This may be due to the fact that either chromium is found on fine particulate matter that is not removed by filtration or total chromium is solubilized by a ' complexing agent at low concentrations • It is not clear if the dissolved total chromium will increase the potential for forming hexavalent chrorrnum during ozone sparging • Hexavalent chromium (if any) formed by oxidation will be reduced to trivalent chromium and drop out of solution • The concentrations of total chromium are unlikely to exceed the observed levels based on an assessment of soli and water geochemistry