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• Feasibility Study/Correctrve Action Plan 2 The Drake Property 26485 Thornton RoaB Thornton California November 26, 1996 During June 1993 UST removal activities, Wallace-Kuhl collected soil and groundwater samples from the southern UST pit Benzene concentrations were non-detect in any soil and groundwater samples analyzed during this investigation (Wallace-Kuhl, 1993) wt Z�6gU °� i PO Z d P0 2, On November 19, 1993, Wallace-Kuhl conducted an additional investigation to further assess the extent of petroleum hydrocarbon impact upon site soils and groundwater Over-excavation of the southern UST pit removed approximately 150 cubic yards of hydrocarbon-impacted soil from beneath the former UST pit and ��'��) dispenser island Exploratory trenches were dug to estimate the lateral extent of hydrocarbon-impacted N K v soil In addition, groundwater monitoring wells MW-1, MW-2 and MW-3 were installed and sampled ND 50 C Benzene was non-detect in a y soil and groundwater samples analyzed in this investigation (Wallace-Kuhl,� 1994 l 9Mddr�f rl�ow lt,i,,l�l �� d �k &fir hr ria �t.v��►... [nom fad 1 d�PsZ7o" G�o,N CX 3-9) ')--&, �`(1 7, rU- Based on the results of the November 1993 investigation,the extent of hydrocarbon-impacted soil was estimated to encompass a 120-square-foot area between the former USTs and eastern pum island (Wallace-Kuhl, 1994) � 15 #-,_ A.,,,,, w6X 3-71 P-G, 4 7-& Gl iuna� I (eq 01. CvV Ln- -Wellhead elevations, obtained during a professional well survey conducted on January 31, 1995, were combined with groundwater monitoring data collected during previous quarters by Wallace-Kuhl to determine the groundwater flow direction beneath the site Based upon the results of the background review and determination of groundwater flow direction, Groundwater Technology, Inc (Groundwater Technology) advanced and sampled soil borings B-1 through B-10 on February 17, 1995 (Figure 2) Groundwater samples were collected from temporary wells installed in the borings The objective of soil and groundwater sampling was to further define the extent of hydrocarbon-impacted soil and groundwater identified during the installation of MW-1, MW-2 and MW-3 (Groundwater Technology, 1995) 9ak�' ' " ^ Nl,i 22 Site Conditions The site is located approximately 8-9 feet above mean sea level and the site topography is flat The site is bordered to the east by Thornton Road and an open field to the south by Walnut Grove Road and a large truck stop (BP fueling facility), to the north by residential property, and to the west by Interstate 5 A drainage ditch (approximately 3-4 feet deep) runs easttwest on the south side of Wainut Gro Road meq* N S IdJ4 r 4 23 Results of Soil Assessment Table 1 summarizes analytical results of soil samples collected on site Soil samples collected at depths of 4 to 9 feet below ground surface (BGS) from the UST excavation in June 1993 by Wallace-Kuhl contained no detectable benzene concentrations, and a maximum total petroleum hydrocarbons-as-gasoline (TPH-G) 0191FEA RPT(M,sc 15) FLUOR DANIEL GTI