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Mr Bill Little (AGE) <br /> I Curtiss Pontiac <br /> December 8, 1999 <br /> I Page 3 <br /> QOMMENT <br />' Physicochemically, most parameters for the soils tested are within the range for microbial <br /> growth and biodegradative activity, however, the pH is relatively alkaline, and may be <br /> contributing to lower general and selective microbial enumeration data observed for most <br />' samples Sample MW7-5 had especially low values for microbial recoveries and may reflect <br /> some localized biotoxicity Lower biodegrader counts were encountered for those samples <br /> tested at the higher (5000 ppm) contaminant concentration, suggesting that this material may <br />' also be exerting some limited biotoxicity (this is frequently found for gasoline-impacted soils <br /> where the solvent-like nature of the constituents can adversely effect microbial cell integrity, <br /> although usually not until the 7,500 ppm level) <br /> 1 In summary, there is evidence that natural bioattenuation is occurring for the majority of soils <br /> tested, albeit at relatively low levels There is a sufficiency of bionutnents to support <br />' continued activity for some time, although periodic monitoring is recommended in order to <br /> ensure that concentrations remain at appropriate levels It is suggested that efforts be taken <br /> to determine whether and to what degree biotoxicity may be present at the site (such as high <br />' salt concentrations, heavy metals, other solvents, etc ) A gradual lowering of pH to more <br /> neutral levels will likely have a beneficial effect on microbial population dynamics and activity <br /> Should you have any questions concerning these results, please do not hesitate to contact me <br /> 1 <br /> AKK em <br /> 1 <br /> • <br /> 1 <br /> S <br />