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will be investigated should (1) oxygen be used and (2) the amount needed be established from a pilot test. If an air compressor were to be used, a building permit would likely not be required, ' but a larger compressor system might be required to supply the same amount of oxygen required. ' As previously discussed, a field pilot test would be conducted. Since the pilot test would utilize almost identical types of equipment, the test would be easily implemented. In addition, the pilot test should be completed within a short period, typically not more than two weeks. Therefore, it ' is not expected to cause any significant delay in the implementation of biosparging at this site. Overall, the implementability of this alternative is considered high. 4.3.3 Cost Major cost elements for implementing biosparging are similar to those of air sparging. The capital cost items are primarily those associated with procuring equipment and material and installing the biosparge system. As mentioned earlier, the primary equipment would be an air compressor or oxygen generator only; the total capital cost should therefore be low compared to those of the previous two alternatives. Pending results of the field pilot test, a ROM cost of a typical biosparge system for the estimated treatment area is expected to be around $30,000. The O&M cost would consist of expenses incurred in periodic system monitoring and maintenance, groundwater sampling and analysis, and utilities (mainly electricity). As most of the groundwater sampling and analytical costs would be incurred under quarterly sampling events, the ROM for an annual O&M cost is likely to be around $10,000. If nutrient supplement is required, the O&M will be greater. In spite of some site-specific uncertainties at this stage, the cost of implementing this alternative is still considered low compared to those of the previous two alternatives. As such, from a cost effectiveness point of view, this alternative is ranked high. 4.4 In -Situ Chemical Oxidation In-situ chemical oxidation (ISCO) is a proven technology that has been employed to treat groundwater contaminated with organics, including petroleum hydrocarbons and BTEX. Therefore, this technology is further evaluated to assess its applicability to treatment of the groundwater contaminants at the site. ' ISCO involves use of a chemical agent to oxidize the organic contaminants in the subsurface to innocuous substances such as carbon dioxide and water. The selection of a chemical agent ' depends on the agent's effectiveness in the oxidation of the specific organic compounds of concern. At this site with TPH-g and BTEX as the COPCs, ozone would be the initial choice of oxidant for the application. Ozone is generally safer to handle and less costly compared to other oxidants such as Fenton's reagent. For ozone, one benefit is the release of oxygen in the process that would also enhance aerobic biodegradation of the organic contaminants (as in biosparging). FS -Onsite Petroleum Hydrocarbon Remediation.doc 4-7 Shaw Environmental, Inc.