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• Clayton <br /> E\Aiur r\WE\I t <br /> t l♦tilf ♦I• <br /> Eeculive Summar► <br /> Clayton Environmental Consultants, Inc., was retained by Orchard Supply Hardwa►e (OSH) <br /> to summarize the results of soil and groundwater investigations and soil remediation <br /> _ conducted at the northeast corner of MacArthur Drive and Grant Line Road in Tracy, <br /> Cahfomia (Figure 1). <br /> Since January 1990, Clayton has completed the following work at the site: <br /> 1 Phase I environmental assessment of approximately 40-acre vacant parcel <br /> 2. Installation of three monitoring wells (MW-1, MW-2, and MW-3) and sampling and <br /> anal)sis of soil and groundwater <br /> 9 <br /> 3 Excavation and aeration of 1,650 cubic yards of soil in the vicinity of a former fuel <br /> pump island and septic tank near the southwest corner of the property <br /> f a <br /> 4 Installation of an additional monitoring well (MW-3B) downgradient of the excavation <br /> and sampling and analysis of sod and groundwater <br /> 5. Installation of five boreholes downgradient of the excavation and sampling and <br /> .� analysis of soil, sampling and analysis of groundwater from MW-3B <br /> Based on completion of the above tasks, Orchard Supply,Hardware requested that San <br /> Ioaquin,County Public Health Services, Environmental-Health,Division (SJCIEHD) <br /> rzzommidhdrsite closure to the Central Valley Regional Water GuafiWControi Board <br /> + (RWQLB) Ms. Laurie Cotulla, Program Manager for the SJC/EHD recommended site <br /> closure in a letter to Ms. Beth Thayer, Associate Engineer for the RWQCB, dared July 16, <br /> r= 1991. <br /> Ms. Thayer responded with several concerns about site closure, which were presented in a <br /> letter dated August 19, 1991. Ms. Thayer's concerns are,listed in italics below, brief <br /> respdnses to,these concerns follow. The body of this report summarizes-'all work-completed <br /> at the-mte by Clayton. As requested by the RWQCB, our mte.itton in preparing this report <br /> was to consolidate-and clarify reports, addendums, letters, and personal communication that <br />` transpired betweemClayton and the SJCJEHD. <br /> About the soil excavation in the vicinity of the former fuel pump island and septic tank, Ms. <br /> Thayer states: <br /> "Contaminants In five soil samples ranged from 60 ppm to 1100 ppm oil and grease <br /> ` hydrocarbons. Apparently, additional lateral excavation (over-excavation) occurred towards <br /> the northeay. However, it is unclear from either the report or the addendum whether the <br /> excavation was extended vertically below 10 S feet" <br /> "Orchard Supply must present a precise description of the over-excavation activities before <br /> closure may he consldered including the following information <br /> f 1 Total depth of excavation below samples MW-1, NW-1, MN-1, NE-1, and ME-1; <br /> F6 <br /> j <br /> S <br /> rwsw.w.r n svAf+pd »• <br />