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I I Hydrogeologic conditions at the site warrant consideration of an alternative to groundwater extraction, (GWE), soil vapor extraction (SVE), and air sparging (AS) because the frequent ' occurrence of clay and silt would limit the remediation potential and cost-effectiveness of those technologies Costs for purchasing, installing, and operating these types of systems for the first year could be on the order of $100,000 to $200,000, and on the order of $50,000 (or more) per ' year to operate thereafter Disruption to the Barnes Trucking facility, and resultant econornic impact, caused by system installations would both be substantial ' It is Clearwater's opinion that the iSOC technology would be a feasible alternative for enhancement of the biodegradation potential at the site The 1SOC technology has been demonstrated to be effective for BTEX, MTBE, and gasoline-contaminated sites with low ' permeability soils The iSOC system is simple to install and maintain, requires no electricity or fuel, generates no wastes, and is easily adaptable to standard 2" PVC wells Installation of several additional wells may be recommended to allow for sufficient plume coverage Effective ' application of iSOC does require operation within water-saturated materials Previous site investigations have demonstrated that a significant majority of sorbed-phase soil contamination ' on the site is located well within the saturated zone — typically 20 to 25 ft below surface grade (bgs) The fine-grained soil types on the site more than likely have appreciable moisture content above the observed water levels — that condition could allow for oxygen diffusion above those observed water levels More specifically, the iSOC will promote biodegrading activity within the capillary fringe zone due to seasonal water table fluctuations, however, the effect of the iSOC would not be expected to be significant within the vadose (unsaturated) zone Nevertheless, a ' majority of the sorbed-phase contamination is indicated to be located well within the saturated zone, and, given the low permeability soil conditions on the site, enhanced biodegradation would be the only remaining method for remediation of the vadose zone without excavation The ' anticipated cost for implementation of an iSOC system at the site would be on the order of $50,000 to $75,000 Annual O&M costs would be expected to be on the order of $2,000 to $3,000 — not including costs for quarterly groundwater monitoring, or any additional biological ' or chemical analysis An overview of oxygen-enhanced bioremediation, and a detailed description of the iSOC technology, including conceptual design for the site, are provided below A summary of remedial alternative comparisons is provided below in Table 1 ' Overview - Bioremediation of Petroleum Hydrocarbons Using Dissolved Oxygen ' The use of dissolved oxygen in contaminated ground water to enhance natural attenuation of gasoline constituents (MTBE and BTEX) has been growing as a remediation technology since the mid 1990's Presently there are a variety of techMologies available which will introduce low ' to moderate concentrations (10-20 ppm) of stable dissolved oxygen into ground water Once this elevated dissolved oxygen mixes with ground water, natural biodegradation occurs and ' the gasoline constituents are consumed by aerobic microorganisms Dissolved gasoline constituents in ground water can be treated by mechanical technologies such as groundwater pump and treat systems (GWE), SVE, or AS Those technologies are appropriate for some ' ZB 178C Addendum to CAP 2 December 31,2003