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0 13 December 1995 AGE-NC Project No. 95-0109 Page 4 of 8 which likely accounts for the low percentage of biodegrading organisms detected. A recommendation for nutrient supplementation to target areas to supplement the observed loss was suggested by the microbiologist. Samples will be collected from monitoring wells MW-8, MW-9, MW-14 and EW-1 and transmitted to a microbiologist for treatability studies. Nutrients will be added to the samples, under laboratory conditions, at various concentrations and combinations, to determine the optimal nutrient additions for the site. From past experience, laboratory studies have indicated that optimum microbial growth is maintained with combined concentrations of oxidized and reduced nitrogen (total nitrogen) at approximately 50 ppm. Present concentrations of nutrients, specifically nitrates, nitrites and ammonium, will be used as"background" or baseline samples. AGE proposes the addition of nutrients to wells MW-8,MW-9, MW-14 and EW-1, since these areas have shown the greatest concentrations of hydrocarbons (specifically benzene). We anticipate the addition of hydrogen peroxide and ammonium nitrate to each well will be in a liquid form. The nutrients will be added to each well in low concentrations, over period of 2 to 4 weeks. It is believed that the addition of high concentrations of nutrients in single injection event reduces the microbial growth at the injection point (i.e., monitoring well) and in the immediate vicinity of the well. As stated above, the specific concentrations of nutrients to be added will be based upon samples collected for treatability studies. The samples will be collected during the week of 18 December 1995; performance of the treatability studies should be completed in approximately two weeks. The addition of hydrogen peroxide to the subsurface will increase oxygen concentrations and enhance aerobic metabolism of petroleum hydrocarbons. As in soil, the addition of ammonium nitrate will provide a supplemental source of nitrogen required to achieve efficient degradational capabilities of the microorganisms. 3.4. MONITORING REQUIREMENT MODIFICATIONS Vapor monitoring has been on-going at the site since remediation was initiated in August 1994. Concentrations of oxygen,carbon dioxide and organic vapors have been monitored in most wells on- site on a weekly,twice-monthly or monthly basis. Attachment C contains graphs of oxygen, carbon dioxide and organic vapor concentrations versus time for selected wells. Although a relationship has been loosely established among CO2-02-OV concentrations in soil vapors, no clear correlation can be made between vapor concentrations and laboratory results of hydrocarbons concentrations in the soil. Monitoring for bioremediation sites should be focused upon data that will provide information on