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before the ORCI was added. Figure 2b illustrates the distribution of oxygen from the ORC®barrier after 9 days Figures 3a and 3b are a cross sectional view of oxygen distribution, at the ORC® source wells during the same time span It is clear that oxygen levels as high as 20 ppm (mg/l) are present It takes a minimum of 1 ppm of oxygen to support bioremediation and higher levels to improve efficiency - according to a fundamental study performed by noted scientists at Shell's Westhollow Research Center (Chang, Salinitro et al. 1989. Ground Water, Vol 2716) Oxygen levels at other sites with minimal demand factors (contaminant flux) have been as high as 34 ppm. This New Mexico site has high demand factors and after 9 days the oxygen distribution is probably impacted to some degree by consumption. It is important to note that the oxygen is distributed in a continuous barrier relative to the placement of ORC® and in accordance with the spatial and temporal factors indicated in the Figure 2b. 9 days after ORC installation, DO concentrations 10 feet downgradient of the barrier were at least 2 ppm, above the level required for bioremediation By the end of the experiment oxygen had arrived at and remediated hydrocarbons at to ND at SH-6 which is 120 feet downgradient In addition to addressing the issue of oxygen distribution, the mass and duration of the oxygen source also becomes important. In a period of three months the oxygen mass increased to a maximum in first 3-5 days and remained relatively constant for the next 30 days. The oxygen mass then decreased to approximately half its mass after three months. During this time, the BTEX mass decreased proportionately as fully explained _ in Technical Bulletin I.2c Based on this data the product would be expected to last at least six months. IREG EN ES I S ------ ---- Bioremediation Products 27130A Paseo Espada, Ste 1407, San Juan Capistrano, CA 92675 Phone 714-443-3136 Fax 714-443-3140 •