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t Advanced GeoEnvironmental, Inc. <br /> Shockey & Sons Trucking <br /> August 12, 1999 <br /> Page 2 <br /> Lower than expected general and selective microbe concentrations were observed for the soil <br /> samples analyzed. Although there is some physicochemical heterogeneity among the samples, <br />' overall concentrations of bionutrients appear to be well within the range expected for microbial <br /> growth and metabolism. Moisture content is relatively low for sample P10-15 however, and <br /> the pH for all soil samples is moderately alkaline. It is likely that such conditions, in particular <br />' pH, have contributed to the lower cell counts. Since neither general or selective organisms <br /> were found for sample P10-20, there may be some biotoxicity associated with soils from <br /> which this sample was collected. Such biotoxicity may be due to high metals concentration, <br />' excessive salt, or other as yet unidentified material. While unlikely, the concentration of <br /> utilizable carbohydrates (food source, either contaminant and/or alternative carbon substrate) <br /> may be limiting and/or biologically unavailable. With the possible exception of materials <br /> associated with sample P10-25, present conditions within the soils at this site do not appear <br /> lie favorable to efficient natural bioattenuation of contaminant. It should be noted however, that <br /> the soil associated with this site may be considered a candidate for directed bioremediation <br /> and/or alternative mitigative technologies. <br />' While levels of bionutrients are comparatively low for the water sample tested, they presently <br /> appear to be of sufficient levels to support microbial growth and metabolism. Both general <br /> (heterotrophic) and selective (contaminant-specific) microbes were recovered from the sample <br /> at levels which suggest ongoing metabolic activity on both contaminant and alternative carbon <br /> substrates. The relatively low proportion of contaminant-specific microbes, as compared to <br />' the overall heterotrophic counts is likely reflective of a lower concentration of contaminant <br /> when compared to other available carbon sources. The conditions in the water appear <br /> supportive of continued natural bioattenuation of contaminant; however, it is recommended <br />' that periodic sampling and analyses of the water be conducted to ensure that levels of <br /> bionutrients are not exhausted prior to bioattenuation completion. <br /> Should you have any questions concerning these results, please do not hesitate to contact me. <br /> AKK:ch <br /> • <br />