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r <br /> r07 November 2003 <br /> a AGE-NC Project No 98-0492 <br /> rPage 7 of 9 <br /> 6 12 Feasibility Testing <br />' A ground water extraction feasibility test has not been performed at the site Data from soil samples <br /> �' Y <br /> collected at the site indicate that poorly graded sands and silty sands are present in the water bearing <br /> rzone impacted with MTBE Poorly graded sands and silty sands typically possess hydraulic <br /> conductivity values that are favorable for ground water extraction However, a ground water <br />' extraction feasibility test would need to be performed to accurately determine well placement and <br /> remedial design and general effectivity of the remedial alternative <br />' 613 Duration <br />' Experience has shown that all systems involving ground water extraction require much more time <br /> than would be anticipated from aquifer tests and calculations of ground water discharge rates, and <br /> the method seldom achieves regulatory goals for ground water clean-up Systems typically operate <br />' for several years During this time,pumps and other equipment may need replacement several times <br /> Currently, the primary utility of pump-and-treat systems is in control migration of contaminated <br /> ground water <br /> I • <br /> 6 1 4 Cost <br />' Ground water extraction is usually a very costly method of ground water treatment Costs for <br /> installation of a "pump and treat" system typically ranges from $40,000 to $65,000, including the <br />' installation of large-diameter extraction wells Once extracted, the contaminated water must be <br /> treated or disposed Treatment is highly dependant upon the concentrations of dissolved MTBE the <br />' ground water, the cost per gallon could be as great as $0 1 based on the extraction/treatment of <br /> approximately 3,000,000 gallons of contaminated ground water Costs for the entire treatment <br /> project would likely be between $100,000 and $300,000 <br /> 62 IN-SITU OZONE SPARGING <br />' The ozone sparge system is an in-situ air stripping and oxidation process utilizing fine bubbles of <br /> ozone injected into saturated soil to extract and decompose dissolved petroleum hydrocarbon <br />' constituents An ozone generator is utilized to produce gaseous ozone which is injected into the <br /> subsurface via microsparge points or fine well screen The "microbubbles" (approximately 50 <br /> micrometers) are forced out into the surrounding saturated soil and react with the target analytes, <br />' producing carbon dioxide and water The frequency and duration of ozone injection periods can be <br /> regulated at the ozone generator control box Initially, operation of the ozone injection system will <br /> be based on the manufacturer's recommendations Injection rates, frequency and duration may be <br />' Advanced GeoEnviron mental,Inc <br /> 1 <br />