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_ 29.April 2005 . _ AGE-NC'Project No. 98-0440 n Page 10.of 18 6.2. -IN-SITU SOIL BIOREMEDIATION Local acceptance of this treatment technology by the regulatory community has grown recently,due " to documented success for remediation of petroleum hydrocarbon contaminants at the site located ' ' at 17. South Cherokee'Lane in Lodi and the Port of Stockton - ST Services (bulk petroleum: distribution).However, the CURWQCB has been reluctant to issue discharge permits required to „ inject bacterial inoculum and/or'nutrients into:the subsurface:. , ' 6.2.1. Principles Hydrocarbon-degrading bacteria:metabolize hydrocarbons'.and assimilate, the.resulting organic , ' chemicals irito biomass for reproduction and growth,and release water and carbon dioxide as waste products. The light-end hydrocarbons. are 'typically consurned first, followed by "heavier" hydrocarbon molecules. ; For in-situ bioremediation, hydrocarbon-degrading bacteria are'propagated in a liquid medium, which is then injected into inoculation wells screened in the interval of.contamination..If ground '. water has been impacted, strategically located ground water monitoring wells can be'used for inoculation. Once in the contaminant plume,'the bacteria metabolize and degrade hydrocarbons and :spread laterally and vertically by migrating and reproducing, thereby creating an advancing remediation front. , 6.2.2. " Nutrient Requirements and Toxicity The. hydrocarbon-degrading bacteria require certain essential nutrients, which are,commonly ' available'in'native soil. If supplemental nutrients are needed,the'quantitic's and concentratibns'are generally very low,comparable to the quantities and concentrations utilized for light agricultural use.. ' There is considerable variation ill the types of bacteria used by different remediation consultants.for .bioremediation. The bacteria are cultured- and selected for-their ability to degrade petroleum hydrocarbons.They are microaerophilic and facultatively anaerobic,and therefore abundantoxygen ' is not necessary;for the process to occur. Exotic-forms of oxygen (such as hydrogen peroxide or . liquid oxygen) are usually not required. ; Free oxygen'increases the metabolic rates of reaction in the bacteria- A small blower delivering . atmospheric air to the subsurface•at a rate of two to five standard'cubic feet per minute (scfm) per well canbe used to enhance air flow and oxygen concentrations during the process. This rhayresult .� in unwanted dehydration of the soil, but'dehydration can be ameliorated by monthly, injection'of ' Advanced GeoEnviroimental,Inc.