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CHP SITE—AD ART RD <br /> 1. Two of four boreholes confirm contamination for MtBE @ 25' below grade surface <br /> (bgs) <br /> 2. No samples were taken within 24' below the tank bottoms nor were any samples <br /> taken at standard five foot intervals as is the case for most assessments <br /> 3. No PID/field screening instruments were used on-site during the installation of the <br /> boreholes to 25'bgs that may have provided additional information as to contaminant <br /> location in reference to depth <br /> 4. MtBE and other similar oxygenates have a very low Koc (organic carbon partitioning <br /> coefficient)values which means these compounds would not be expected to adsorb to <br /> soil, particularly sands and silty sands as are present at this site,the compounds are <br /> likely to migrate freely and not attenuate (decrease in concentration over any unit <br /> length) laterally or vertically <br /> 5. MtBE hits create a question. Is this a new release which may become a larger <br /> problem over time?Or an old release which has passed through the soil/vadose zone <br /> and down to the water table? In either case a release has occurred. <br /> 6. More site definition work should be performed <br />