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V r � �. Groundwater extraction is typically a suitable remedial method to employ as a "polishing" effort following completion of more rigorous remedial methods. Given that the focus of remediation will be on the groundwater, this treatment option is proposed to be evaluated for possible later implementation. 3.1.2 In-Situ Treatment Options Air Spa rging This treatment option involves the introduction of air below the water table to ` volatilize hydrocarbon vapors and to stimulate natural biodegradation due to the added oxygen. Air is introduced to the subsurface through an injection well(s) installed at a strategic location. The well is outfitted with a bubble diffuser which allows the generation of minuscule air bubbles, thus extending the residence time that the air remains in contact with the contaminants_ The concentration gradient between the contaminant-laden water and the air results in partitioning of the �- contaminants into the air bubbles. The air bubbles then migrate upward through the formation, where they can be collected and extracted using vapor extraction technology as an option depending on groundwater depth, lithology, and site r.. conditions. Biodegradation Augmentation As mentioned previously, given sufficient time, the contamination would degrade in the presence of adequate biotic stimuli. However, this process would typically take many years. Biodegradation rates can be greatly accelerated by augmentation of the factors which tend to limit degradation rates. The most common rate-limiting factor is the limited availability of oxygen. Introduction of supplemental oxygen into the subsurface, such as with bioventing and air sparging, oftentimes is sufficient to stimulate an increase in biodegradation. Additionally, more potent oxygen concentrations can be introduced by means of oxidizing compounds. One such common method is the F use of Oxygen Release Compound (ORC(D). ORCO introduces high concentrations of oxygen into the formation at a steady rate. Lo There are no empirical pilot tests to evaluate the effectiveness of biodegradation augmentation. Typically, effectiveness is determined via actual field testing �- performed over a period of approximately three to six months. However, the success of ORCO has been fairly well demonstrated at a number of sites such that it would be safe to assume it to be effective for this site, if it can be �. appropriately fine-tuned to site conditions. Ozone Injection y Ozone injection technology incorporates the use of injected ozone to enhance subsurface contaminant oxidation (degradation). This technology is similar to L. biodegradation augmentation, except that contaminant degradation occurs through chemical, rather than biotic, oxidation processes. Studies suggest high success rates and fairly rapid contaminant degradation. Further, once installed, w 4 JJW GEOSCIENCES Inc.