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Gealagfca[TecknusW Page 3 Site Conceptual Model Report(2006 Revision) Valentine(Castle Motors) Project No 723 2 June 16,2006 ' The data compiled during the course of this investigation indicate that the soil and p groundwater were impacted with gasoline range petroleum hydrocarbons In their April 29, ' 2002 letter correspondence the SJC/EHD directed that that a work plan be submitted for additional site characterization and that the plan include a Site Conceptual Model (SCM) GTI responded by submitting our first SCM for the site in our June 27, 2002 "Additional Site ' Characterization" work plan The SCM did not include estimates of contaminant mass in soil and groundwater because the off site plume definition had not occurred After three continuous multi-chambered tubing (CMTrm) wells were installed off site in November 2003 ' the site conceptual model was updated in GTI's January 21, 2004 "Additional Site Characterization Report, Soil and Groundwater Investigation" This report contained contaminant mass estimate calculations and estimates for the quantity of gasoline in the soil plume After the November 2003 well installation activities, the down gradient plume definition was still incomplete to the northeast ' In our March 15, 2005 "Soil and Groundwater Investigation" work plan, GTI proposed using Cone Penetrometer Testing (CPT) in order to define the down gradient extent of the gasoline impacted groundwater GTI's May 9, 2006 "Additional Site Characterization Soil & Groundwater Investigation" report detailed the completion of three CPT borings (CPT 1 — 3) to the northeast of the subject site in February 2006 The following sections present the updated Site Conceptual Model -- June 2006 Revision based on the data gleaned from the CPT borings in the context of the rest of the data gathered todate ' 2.0 ASSESSMENT OF IMPACT ' 2.1 Release Documentation The SJC PHS/EHD completed an underground storage tank (UST) unauthorized release form for the site dated May 4, 1988 The report states that April 20, 1987 was the date the contamination was discovered at the site during UST removal activities and that the start of the discharge is unknown In their August 18, 1993 letter correspondence, the SIC PHS/EHD reiterated that the property has been placed on file as an unauthorized UST release (leak) site and that corrective action is required Both of these documents are included in Appendix A ' Significant soil contamination has been recorded in the vicinity of the former dispenser island that appears to be the release point of the gasoline into the subsurface ' GTI has not performed a review of any underground storage tank removal activity documentation on file at SIC PHS/EHD A file review should only be performed if ' additional release data is necessary to achieve site closure