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Report of Secondary Investigation 2 <br /> Prepared for Barbara Drake 28485 Thornton Rd Thornton CA May 4 1995 <br /> were removed by mistake in 1975 The USTs located in the southern UST pit were removed on <br /> June 2, 1993 (Wallace-Kuhl and Associates[Wallace-Kuhn, August 18, 1994) <br /> During tank removal In 1993, soil samples were collected beneath the eastern ends of the USTs <br /> located in the southern UST pit Detectable concentrations of TPH-G were detected in the soil samples <br /> collected beneath the USTs and in water samples collected from the UST pit Additional Investigation <br /> was conducted by Wallace-Kuhl in November 1993 Over-excavation of the UST pit removed <br /> approximately 150 cubic yards of hydrocarbon-Impacted soil from beneath the former UST pit and <br /> dispenser island Exploratory trenches were dug to estimate the lateral extent of hydrocarbon-impacted <br /> soil In addition,three groundwater monitoring wells were installed and sampled <br /> Based on the results of the November 1993 Investigation,the extent of hydrocarbon-Impacted soil was <br /> estimated to encompass a 120-square foot area between the former USTs and eastern pump Island <br /> (Wallace-Kuhl,August 18, 1994) Analytical results of groundwater samples collected from the <br /> monitoring wells Indicates the presence of dissolved hydrocarbons in groundwater in two of the three <br /> on-site wells <br /> As a result of the November 1993 Investigation, Groundwater Technology performed additional <br /> assessment to Identify effective locations for future monitoring wells that will define the lateral extent of <br /> dissolved hydrocarbons in groundwater In addition,soil samples collected during the Investigation <br /> would be used to confirm the extent of hydrocarbon-4mpacted soil estimated by Wallace-Kuhl prior to <br /> excavation <br /> 3 0 PRE-FIELD ACTIVITIES <br /> Pre-field activities include tasks completed pnor to initiating fieldwork The tasks for this site Included <br /> background review,wellhead surveying, access agreement procurement and permitting Also provided <br /> is a discussion of the rationale behind the location of each borehole <br /> 3 1 Background Review <br /> Groundwater Technology conducted a technical review of all relevant Information available prior to <br /> proceeding with site assessment work Groundwater Technology reviewed the Prehminary <br /> lnveshgahon and Evaluation Report, dated August 18, 1994 (Wallace-Kuhl) and the Quarterly Status <br /> Report for the November sampling event, dated December 8, 1994, as well as field notes recorded by <br /> Wallace-Kuhl personnel during the excavation of the former UST pit and exploratory trenches Data <br /> reviewed provided information as to the location of remaining sources of hydrocarbons as well as the <br /> magnitude of concentrations of hydrocarbons in both soil and groundwater In addition, Groundwater <br /> Technology has had numerous conversations with the former property owner regarding the history of <br /> the site and location of former gasoline-related facilities on site <br /> i <br /> 0053EAR RPT <br /> ❑❑ j GROUNDWATER <br /> ❑❑❑ TECHNOLOGY <br />