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r . Oxygen Release Compound,ORC® A Case Study of Oxygen Distribution in an Aquifer The most important and frequently asked questions with regard to ORC pertain to how the oxygen that is released gets distributed into the aquifer. Essentially we are asked - "Where does the oxygen go?", with the implicit understanding that aerobically remediable compounds will be readily degraded when the oxygen arrives. The question can be answered from either an experimental or a theoretical perspective. Experimental evidence is always best, however, the specific results do not apply universally to all site conditions. Models are therefore employed which attempt to extend the observations from experimental results to any given case. This Technical Bulletin focuses on actual experimental oxygen distribution data from a major barrier project, commissioned by the New Mexico Environment Department, for a site near Albuquerque. Technical Bulletin IV.2 discusses the theoretical basis of oxygen distribution in an aquifer as governed by advection, dispersion, retardation and utilization. Technical Bulletin VI.3b presents a series of outputs from the Cleary-Ungs model that considers these factors and their combined effect on oxygen distribution. The complete _ results of the BTEX remediation, as a function of oxygen availability at the New Mexico site, are discussed in Technical Bulletin I.2c. The intent here is to illustrate the isolated dynamics of oxygen distribution, independent of demand, in answer to the question "Where does the oxygen go?". At an abandoned gas station site near Albuquerque (Figure 1 a) a full scale remediation system was installed consisting of twenty 6-inch ORC® source wells and 54 monitoring points downgradient of the source wells (Figure lb). The vertical distribution of dissolved oxygen(DO) and BTEX was measured with probes located 3, 10, and 17 feet below the water table at the source and at variable depths with the monitoring points. A total of 342 ORC®filter socks were installed and the system was monitored to determine changes in DO and BTEX during the first three months. A large volume of data was collected to determine the interaction between the ORC® derived oxygen and the existing BTEX plume. For the purposes of this discussion, we will isolate the oxygen distribution as much as possible from the consumption factors - in order to show that oxygen becomes available and migrates downgradient in an effective manner. Figure 2a is a contour plot illustrating oxygen status in the study area