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G2010gkat'r"Oda Inc, Page 2 Sinclair Trucking Project No.: 1030.2 August 11,2005 consolidated batholithic and metamorphic rocks are poorly transmissive, however the overlying sedimentary layers are often quite permeable. These unconsolidated layers include Pliocene/Pleistocene age continental deposits, Pleistocene age lacustrine and marsh deposits, ' and Holocene older and younger alluviums and flood-basin deposits. 1.2 Site Background On March 31, 1989, one steel 250- allon underground derground storage tank (UST), used to supply leaded gasoline, was removed from the site. The SJCEHD inspection report indicated that corrosion was present on the UST and a petroleum odor was noticeable in the area of the tank removal. Subsequent laboratory soil analyses indicated the presence of petroleum hydrocarbons at the site. A limited over excavation to a depth of 18-feet bgs was conducted ' in the general area of the UST and was backfilled with native soil. On June 14, 1995, Geological Technics Inc. (GTI) installed three monitoring wells and ' advanced one soil boring in order to evaluate the vertical and lateral extent of gasoline range petroleum hydrocarbons. ' On February 16, 1999, GTI personnel supervised the installation of one groundwater monitoring well down gradient of the former UST to further define the lateral extent of gasoline contamination in the soil and groundwater. This well showed low levels of gasoline range hydrocarbons. In response to a request by Mr. Ron Rowe of SJCEHD, GTI prepared a work plan on January ' 18, 2000, to define the lateral extent of the soil and groundwater contamination at the site. On April 20, 2000, Ms Lori Duncan, SJCEHD, issued a letter denying the approval of the ' work plan. During phone conversations in May of 2000, Ms Duncan requested that a work plan be prepared for the installation of a deeper monitoring well near the source to define the vertical extent of the contamination and the installation of a sentinel well between the source ' and the domestic well. GTI submitted a new work plan on June 9, 2000, proposing the installation of a single deep monitoring well. Ms Duncan approved the work plan on June 28, 2000, A delay in the work plan implementation occurred due to a change in the Responsible Party and cost pre-approval for the work was obtained on October 28, 2001. ' In April of 2002, GTI and V&W Drilling, Inc. (V&W) installed one deep monitoring well to 35 feet below grade (MW-101). On June 18, 2002, GTI prepared and submitted the Site Characterization, Monitoring Well Installation and Groundwater Monitoring Report documenting the work performed during April of 2002. The report recommended continued' groundwater monitoring as well as testing for biodegradation indicators. In a letter dated July ' 22, 2002, Ms Duncan approved the recommendations. On September 30, 2002, GTI prepared and submitted the 3rd Quarter 2002 Groundwater Monitoring Report recommending the site be considered for closure. In a letter dated March