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' 11 February 2003 • ' -AGE-NC Project No. 98-0520 ' Page I 1 of 21 ; ' There is considerable variation in 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 abundant oxygen is not necessary for the process to occur. Exotic fbims 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 can be used to enhance air flow and oxygen concentrations during the process. This may result ' in unwanted dehydration of the soil, but dehydration can be ameliorated by monthly injection of distilled water to each well. ' The hydrocarbon-degrading bacteria are also tolerant to a wide range of soil conditions. For instance,,pH can range from 4.0 to 9.5 and electrical conductivity has little or no effect unless sodium concentrations exceed 5% on a weight basis. . 6.3.3. Inoculation Wells The effective radius of influence in soil of inoculation wells is typically 15 feet.Existing monitoring ' wells can be used for inoculation of the smear zone as well as ground water, but the inoculum will tend to go to the bottom of a monitoring well and pass into the saturated ground water zone from the annular space near the bottom.Although a greater radius of influence is usually obtained for ground ' water inoculation, since ground water movement can assist the bacterial migration, additional inoculation points would be needed for in-situ soil treatment of the vadose zone,utilizing temporary inoculation points or soil borings. 6.3.4. Monitoring Activities After inoculation, the inoculation wells and ground water monitoring wells should be monitored over a period of several months through periodic field measurements of organic vapor, carbon dioxide, and oxygen concentrations. Quarterly or semi-annual monitoring activities should also , ' include the installation of soil borings to collect soil samples to monitor bacterial populations, nutrient availability and soil remediation progress.If monitoring indicates areas of slow remediation, ' additional inoculation or addition of nutrients may be required. - 1 Advanced CeoEnvironmental,Inc.