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Mr Tim Cuellar (AGE) <br /> Sierra Lumber <br /> July 2, 1999 <br /> Page 2 <br /> COMMENT <br /> Physicochemical values associated with the samples submitted for analyses are well within <br /> the range necessary for microbial growth and development Differential microbial analyses <br /> revealed average concentrations of general (heterotrophic) microorganisms for both samples <br /> While both samples yielded detectable levels of selective (contaminant-specific) microbes, the <br /> proportion of biodegraders was significantly lower for sample EW 1-25 Such a result <br /> suggests that the contaminant-based carbon source has become limiting either because of very <br /> low absolute concentrations of the contaminant, and/or because of limited bioavailability It <br /> is also possible that these soils may contain alternative carbon sources which could act as <br /> competitive substrates, thereby minimizing the development of a substantial contaminant- <br /> specific microbial subpopulation In such cases, these alternative food sources (such as <br /> organic debris) which may be in the soils become the dominant food source for native <br /> microorganisms, hence the higher general count associated with this sample A 10% <br /> biodegrader concentration for sample MW8-25 suggests that microbial metabolism of the <br /> contaminant is occurring (via natural bioattenuation), and will likely continue to occur so long <br /> as the necessary bionutrients and physicochemical conditions remain adequate to support <br /> growth <br /> Should you have any questions concerning these results, please do not hesitate to contact me <br /> AKK em <br /> I <br /> I <br />