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l( , <br /> t <br /> s <br /> w <br /> CHAPTER 17 <br /> Technological Limits of Groundwater <br /> Remediation: A Statistical Evaluation 'IMethod <br /> a <br /> William A Tucker and Erin N Parker, Environmental Science & Engineering, Inc , <br /> Gainesville, Florida <br /> z <br /> INTRODUCTION <br /> The most commonly used groundwater restoration technology at sites where <br /> F petroleum hydrocarbons have been released is extraction and aboveground treat- <br /> ment of the groundwater(pump-and-treat) At many sites where this technology <br /> has been used, hydrocarbon removal rates follow a relatively consistent pattern <br /> after a period of initially steady reductions,groundwater contaminant concentra- <br /> tions tend to level off and remain fairly constant,with random fluctuations around <br /> a "leveling off" concentration, or asymptotic limit <br /> The asymptotic concentration levels may be higher than specified cleanup tar- <br /> get concentrations Figure 17 1 illustrates the phenomenon at a site undergoing <br /> pump-and-treat groundwater restoration The data are from one of several repre- <br /> sentative data sets utilized in this study li <br /> K Based upon the observed pattern,the site remediation manager might reevalu- <br /> ate whether the continued operation of the existing remedial system would be <br /> cost-effective Decisions to discontinue or modify remedial activities at a site <br /> should be made in a broad context considering regulatory standards, techno- <br /> logical feasibility and cost-effectiveness, and site-specific exposure and risk <br /> assessment <br /> 'f I <br /> 295 <br />