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Ms. Vicki McCartney ProjectNo.: 880.040.1A.0110 <br /> May 23, 2003 <br /> Page 4 <br /> Effluent concentrations of TPHg, benzene, and MtBE at',the start of.the DPE test were <br /> 460, 49, and 3,800 µg/L, respectively. At the end of the test, effluent concentrations of <br /> TPHg, benzene and MtBE were 420, 4.5, and 1,600 µg/L, respectively, and the <br /> concentrations in well MW-1 Were 1,300, 260, and 9,900 µg2,respectively. At the start <br /> of the DPE test, TPHg, benzene, and MtBE were not detected in vapor extracted from <br /> well MW-1. At the conclusion of the test, TPHg, benzene, and MtBE concentrations in <br /> extracted vapor were 640, 1.4, and 77 (mg/m3), respectively. a,.< <br /> SITE CONCEPTUAL MODEL <br /> Release Scenario andPlumeCharacterizationA . pis° <br /> ' b�l`o ` 1�►�°�11 � � <br /> �t'l�lm <br /> 0- Shallow soil" at the subject site has been impacted with fuel hydrocarbons at <br /> �r 1 " concentrations up to 2 8 g 'df TPHg, 0.0272 n kf benzene, and 49.4 r &L"of <br /> MtBE. The highest hydrocarbon concentrations have been present in soil beneath the <br /> western dispenser islands. Historical soil analytical data are included in Appendix C. <br /> Hydrocarbons have been reported in groundwater beneath the site at concentrations up to <br /> 25,700 µg/L of TPHg, 1,820 µg/L of benzene, and 41,000 µg/L of MtBE.. The highest <br /> hydrocarbon concentrations have been present in well MW-1. ' The highest MtBE <br /> concentrations have been reported in wells MW-1 and MW-5. Currently, TPHg are <br /> observed at concentrations up to 5,800 µg/L in wells MW-1 and MW-3. <br /> Benzene concentrations up .to 760 µg/L are observed in wells MW-1 and MW-2, while <br /> MtBE is reported�at concentrations up to 29,000 µg/L in all wells,. Historical <br /> groundwater analytical data are presented in Appendix C. Summary graphs of chemical <br /> concentration and groundwater elevation trends are presented in Appendix D <br /> Potential Environmental Receptors <br /> The hydrocarbon plume extends beneath the area that is currently being used for <br /> i <br /> commercial purposes (gasoline sale) and transportation (West Hammer Lane). Most of <br /> this area is paved with asphalt or concrete. No residential buildings are located within <br /> the probable extents of the plume. No water producing wells are located within .. <br /> 2,000 feet of the subject site. <br /> i <br /> SHAW ENVIRONMENTAL,INC. <br /> N:\sacDP\2003\Prj\880\8800401 A.3ac.doc <br />