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I , I � I f 16 1 _ , I 28 February 1997 i AGE-NC Project No 95-0144 Page 16 of 20 6 2 3 FEASIBILITY TESTING ,Aquifer testing has not,been performed at the site However, sand is present from just below the ' ground water surface to 18 feet below ground water surface f i l There are several disadvantages to "pump and treat' methods The most serious disadvantages include 1) extended cleanup periods, resulting in increased total costs, although the maintenance for this method is relatively cost-effective and 2) regulatory cleanup goals are rarely attainable, mostly due to persistent hydrocarbons detected in subsequent sampling events Gr6und water T' ' extraction is generally not a desirable method for remediation However, this technology is useful for hydraulic control to prevent spreading of the contaminant plume 6 2 4 DURATION` Experience has shown that all systems involving ground water extraction require much more time than would be anticipated from aquifer tests and'calculations of ground water discharge rates, and ' seldom achieve regulatory goals for ground water clean-up Systems typically operate for, several , years During this time,pumps and other equipment may need replacement several times Currently, the primary utility of pump-and-treat systems is in control migration of contaminated grourfd water E i 6 2 5 COST Ground water extraction is usually a very costly method of ground water treatment Costs for' installation of a"pump and treat" system typically ranges from $20,000 00 to $30,000 00,including 'the installation of one or more large-diameter extraction wells Once extracted, the contaminated water must be treated or disposed Treatment is highly dependant upon the concentrations of dissolved hydrocarbons in the ground water For the Chase Chevrolet - Madison site, the cost per gallon could be as great as $2 00, based upon the extraction/treatment of approximately 100,000 ; gallons of contaminated ground water Costs for the entire treatment project would likely be between $100,000 00 and $300,000 00 S i t , f ' 6 3 IN-SITU BIOREMEDIATIONBIOENHANCEMENT i f 6 3 1 BASIC PRINCIPLES 1 , Bioremediation involves the introduction of hydrocarbon-degrading microbes and/or supplemental nutrients to enhance naturally-occurring bacteria,through wells into the ground water The microbes I r i