ARCHIVED REPORTS XR0010492 - Laserfiche WebLink

Home Browse Search

' BIOPHYSICAL LABORATORY RESULTS A number of physical, chemical and biological tests were run on soil samples to provide data ' on leaching potential, adsorption potential and biodegradation potential In the event that residual soil contamination had been detected the data would have been used to model the effects of vertical transport and degradation on contaminant reduction ' Biodegradation Potential IBiological amenability tests were run on two soil samples from boring MW 1, from an elastic silt/Iean clay at depth of 25 feet (MW1-25 5) and a second elastic silt/lean clay at a depth of 45 feet (MW1-45 5) These samples were selected for biological testing because boring MW1 was Iocated in the area of formerly identified soil impact Analyses consisted of heterotrophic plate count (bacteria) and PKN The results of the physical and chemical/biological parameters, presented in the laboratory analysis reports included in Attachment D, indicate a relative abundance of organic nitrogen (TKN), phosphorus and potassium Nitrate and nitrite were not detected The levels of PKN nutrients are sufficient to support bacterial degradation of several hundred parts per million of gasoline hydrocarbons, if such were present Bacterial counts were well below the 10' colony I forming units typically encountered in an active colony of hydrocarbon degrading bacteria The conclusion drawn from these results is that a suitable substrate exists for biodegradation of the hydrocarbons formerly identified at the site and that degradation has proceeded to completion Adsorption_ and_Leachipg Potential ' Leachability and adsorption potential tests were also run on soil samples collected from the upper and lower elastic silt/lean clay units In addition to the bioamenability tests run on samples MW 1-25 5 and MW 1-45 5, TOC was determined as an indicator of adsorption potential TOC Iwas 0 17% in the sample from 25 5 feet, a relatively high quantity from a silt/clay at depth and indicating a relatively high adsorption potential, the sample from 45 5 feet contained 0 031% ITOC In addition to TOC, physical analyses were conducted on samples collected from the two silt/clay units Grain size analysis of samples MW1-50 and MW3-25 5 indicate that the units are actually a clayey silt Total porosity in the samples ranged from approximately 30 - 45% with effective porosity only 2 to S% Vertical hydraulic conductivity in the upper unit is only I 9 x 10-8 cm/sec These data, along with the TOC content of the upper unit describe extremely effective barriers to vertical transport of any contaminant Laboratory data sheets are included in Appendix D groun&elnormaclsumrepor 45 5 I