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before the ORC® was added Figure 2b illustrates the distribution of oxygen from the <br /> ORC® barrier after 9 days. Figures 3a and 3b are a cross sectional view of oxygen <br /> distribution, at the ORC® source wells during the same time span <br /> • It is clear that oxygen levels as high as 20 ppm (mg/1) are present It takes a minimum <br /> of 1 ppm of oxygen to support bioremediation and higher levels to improve efficiency - <br /> according to a fundamental study performed by noted scientists at Shell's Westhollow <br /> Research Center (Chang, Salimtro et al. 1989 Ground Water, Vol 27/6). Oxygen <br /> levels at other sites with minimal demand factors (contaminant flux) have been as high <br /> as 34 ppm This New Mexico site has high demand factors and after 9 days the oxygen <br /> distribution is probably impacted to some degree by consumption <br /> It is important to note that the oxygen is distributed in a continuous barrier relative to <br /> the placement of ORC® and in accordance with the spatial and temporal factors <br /> indicated in the Figure 2b 9 days after ORC installation, DO concentrations 10 feet <br /> downgradient of the barrier were at least 2 ppm; above the level required for <br /> bioremediation By the end of the experiment oxygen had arrived at and remediated <br /> hydrocarbons at to ND at SH-6 which is 120 feet downgradient <br /> In addition to addressing the issue of oxygen distribution, the mass and duration of the <br /> oxygen source also becomes important In a period of three months the oxygen mass <br /> increased to a maximum in first 3-5 days and remained relatively constant for the next <br /> i30 days The oxygen mass then decreased to approximately half its mass after three <br /> months During this time, the BTEX mass decreased proportionately as fully explained <br /> in Technical Bulletin 12c. Based on this data the product would be expected to last at <br /> least six months <br /> I <br /> H EG EN ES I S __------------------------- ----------- <br /> Bioremediation ProdUcts 27130A Paseo Espada, Ste 1407, San Juan Capistrano, CA 92675 <br /> Phone 714-443-3136 Fax 714- 443-3140 <br />