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ATC Associates Inc. 1117 Lone Palm Avenue,Suite 201 Modesto,California 95351 209-579-2221 fax:209-579-2225 ASSOCIATE S I N C . On September 11 and 12, 2003, a 500-gallon used oil UST was excavated and removed from the site by Walton Engineering, Inc. Petroleum hydrocarbons and metals were detected in a soil sample collected base of the UST from a depth of approximately seven feet bgs. Refer to Grayland Environmental's Underground Storage Tank and Fuel Dispenser Removal Report, dated October 16, 2003, for more information. ATC supervised the advancement of two vertical soil borings on-site utilizing cone penetration testing (CPT) methods on October 14, 2004. The borings identified as CPT-1 and CPT-2 were `, 4 advanced to approximately 80 feet bgs. Soil samples were collected within the capillary fringe- from each boring and one additional soil sample was collected from approximately 40 feet bgs.— G pT'2 Petroleum hydrocarbons were detected in the groundwater samples collected from CPT-2. .`0,4(141,71 On December 2, 2004, ATC supervised the advancement of five soil borings, SB-1 through SB- 5, to approximately 10 feet bgs. Three of the borings (SB-1 through SB-3) were advanced on- site and two borings (SB-4 and SB-5) were advanced west of the site along Holly Drive, for the purposes of evaluating the lateral extent of petroleum hydrocarbon impacted soil and groundwater. A sixth boring was attempted but probe refusal was encountered. Petroleum hydrocarbons were detected in soil and groundwater samples collected from SB-2 through SB-4. The borings was abandoned and filled to the surface with neat grout. A workplan titled Workplan for Vertical and Lateral Subsurface Investigation, Former Cheaper Store #37, 15 East Grant Line Road, Tracy, California, Local Oversite Program (LOP) #1404 dated July 17, 2008. The proposed scope of work described in the workplan included the installation of seven groundwater monitoring wells at the site. The proposed locations of the wells and their respective screened intervals were selected to evaluate the lateral and vertical extent of petroleum hydrocarbon impacted groundwater in three separate water bearing zones identified by previous subsurface investigation activities at the site. In August 2008, ATC submitted a report titled Sensitive Receptor Survey Report for Former Cheaper Store #37, 15 East Grant Line Road, Tracy, California and a report titled Trend Analyses, Former Cheaper Store #37, 15 East Grant Line Road, Tracy, California, Site Code #1404. In the sensitive receptor report, ATC concluded that the contaminant plume has not yet been fully defined to the north in the shallow water bearing zone. Sensitive receptors located east and south of the site are not generally at risk and based on proximity to the site, the water supply wells observed in the vicinity of the site are not likely to be impaired by the petroleum hydrocarbon impacted groundwater plume. In the trend analyses report, ATC concluded that soil and groundwater beneath the site continue to be impacted by petroleum hydrocarbons as observed in samples collected from MW-1 and MW-4 through MW-8 and that shallow groundwater beneath the site has predominantly been reported to flow toward the north commonly with variations to the northeast and northwest and on occasion shallow groundwater beneath the site has been reported to flow toward the south and southwest. An evaluation of remedial alternatives for petroleum hydrocarbon impacted soil and groundwater beneath the site is warranted. SAEnvironmenta1\25847\37 Tracy\Reports\Response 2009 Aug.doc 3