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u <br /> i <br /> r i r <br /> _ w i <br /> 15 February 2000 <br /> AGE-NC Protect No 98-0448 <br /> Page 27 of 33 <br />' 9 2 2 Feasibility Studies <br /> There are several disadvantages to "pump and treat" methods The most serious disadvantages <br />' include 1) extended cleanup periods, resulting in increased total costs, although the maintenance <br /> for this method is relatively cost-effective and 2) regulatory cleanup goals are rarely attainable, <br /> mostly due to persistent hydrocarbons detected during subsequent sampling events Ground water <br />' extraction is generally not a desirable method for remediation, however this technology,is useful for <br /> hydraulic control to prevent spreading of the contaminant plume or to capture MTBE-impacted <br /> groundwater MTBE is not a contaminant of concern at the site <br /> 1 <br />' 9 2 3 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 /> seldom achieve regulatory goals for ground water clean-up Systems typically operate for several <br /> years During this time, pumps and other equipment may need replacement several times A <br /> treatment period of 12 to 24 months is estimated for the site <br />' 9 2 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 $25,000 to $40,000 Once extracted, <br /> the contaminated water must be treated and/or will require disposal Treatment is highly dependant <br /> upon the concentrations of dissolved hydrocarbons in the ground water, the cost per gallon could be <br />' as great as$2 00 Based upon the extraction/treatment of approximately 229,268 gallons(See Section <br /> 6) of contaminatM ground water Costs for the entire treatment project would likely exceed <br /> $498,536 <br /> 1 r r <br /> 9 3 IN-SITU BIOREMEDIATION/BIOENHANCEMENT <br /> Bioremediation involves the introduction of hydrocarbon-degrading microbes or supplemental <br />' nutrients to enhance naturally-occurring bacteria, through wells into the ground water The microbes <br /> degrade hydrocarbons and spread laterally(and vertically) by migration and reproduction <br />' Hydrocarbon-degrading microbes are able to metabolize hydrocarbons and assimilate the resulting <br /> orga,nic chemicals into biomass for reproduction and growth Typically, the light-end hydrocarbons <br /> are degraded first, followed by heavier compounds <br /> Advanced GeoEnvironmental,Inc <br /> 1 <br />