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ATC Associates Inc. vv 1117 Lo e Palm Avenue, Suite 201 Modesto, California 95351 209-579-2221 y ASS O C I ATE S I N C . fax: 209-579-2225 located east of the former UST location, and B20 and B21 located off-site to the southwest and south, respectively. Petroleum hydrocarbons were detected in each groundwater sample except y for B14, B20, B21, MW1, MW2, MW3, MW6, and MW7. Monitoring well MW4 was not sampled due to the presence of approximately 0.02 inches, of free product. The reported groundwater flow direction on September 25, 1995, was approximately due north. Refer to the report prepared by P.E.S. titled Environmental Site Investigation Methods and Findings: Drilling of Soil Borings, Drilling and Installation of Groundwater Monitoring Wells Collection and Analyses of Soil and Groundwater Samples, dated November 17, 1995, for more information. V In a letter dated April 11, 2002, the SJCEHD indicated that groundwater sample collection from up-gradient monitoring wells MW2 and MW3 could be reduced to annual and that the lateral and vertical extent of soil contamination remained undefined. The SJCEHD requested submittal of a Workplan to define the lateral and vertical extent of soil contamination. In response to the SJCEHD request, H2OGEOL submitted the Work Plan for Additional Soil Characterization dated June 10, 2003, which proposed advancing 14 hand auger borings for collecting soil samples. V 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 beneath the UST at 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. y In September 23 and 24, 2003, H2OGEOL collected groundwater samples from MW1 and MW4 through MW8. Petroleum hydrocarbons were detected in groundwater samples collected from each well. The reported groundwater flow direction was to the north. Refer to H2OGEOL's Third Quarter, 2003 Groundwater Monitoring Report, dated October 31, 2003, for more information. y In a letter dated November 14, 2003, the SJCEHD indicated that the proposed scope in the H2OGEOL Workplan was not adequate or necessary. The SJCEHD requested that a Workplan be prepared in the context of a site conceptual model that included analytical data collected during removal of a waste oil tank from the site in September 2003. The requested Workplan was submitted by ATC on February 2, 2004. ATC supervised the drilling of two cone penetration testing (CPT) borings (CPT-1 and CPT-2) on October 14, 2004. The work was completed by Gregg Drilling & Testing Inc. The CPT cone and rods were advanced to 80 feet bgs using a hydraulic press. Groundwater samples were manually collected from within the CPT push rods using disposable polyethylene bailers. Select y soil samples were also collected adjacent to each CPT boring using a direct-push, piston-type sampling device capable of collecting undisturbed discrete samples. r 3 ATC Associates Inc. S:\Environmental\25847.0037\Work Plan additional vert-hor delineationTH2.doc y