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ATC Associates Inc. 1117 Lone Palm Avenue,Suite B Modesto,California 95351 209-579-2221 ASSOCIATES i N c. fax: 209-579-2225 monitoring wells MW 1, MW2, and MW3. The soil sample collected from boring MW2 at a depth of 35.5 feet bgs contained the highest concentrations of TPHg, ethyl benzene, and xylenes. The soil samples collected from boring MW2 at depths of 30 feet bgs and 55 feet bgs contained only trace concentrations of TPHg, ethyl benzene, and/or xylenes. The soil samples collected from borings MW 1 and MW3 at depths of 35 feet bgs contained trace concentrations of xylenes and TPHg, respectively. The samples collected from borings MW 1 and MW3 at depths of 40 feet bgs did not contain detectable concentrations of TPHg or BTEX. MTBE, t-amyl methyl ether (TAME), t-butanol (TBA), ethyl t-butyl ether (ETBE), di-isopropyl ether (DIPE), 1,2- dichloroethane (1,2-DCA), or 1,2-dibromoethane (EDB) were not detected in any soil samples collected from borings MW 1, MW2, and MW3, though the detection limits were elevated in the MW2 sample from 35.5 feet bgs due to the high concentrations of TPHg noted previously. In July and December 2003, ATC conducted additional subsurface investigation activities at the site that included cone penetration testing, advancing a soil boring (SB8), and installation of monitoring wells MW4 through MW7. Petroleum hydrocarbons were detected in soil samples collected from the boreholes of MW5 and MW6, and in the groundwater samples collected from MW4 through MW-7. In November and December of 2005, an ATC geologist supervised the advancement of five soil borings (SB9 through S1313) to approximately 50 to 56.5 feet bgs. Two soil samples collected from each boring were submitted for laboratory analyses. TPHg was detected in the soil sample collected at approximately 50 feet bgs from SB9 at a concentration of 1.6 mg/kg. Petroleum hydrocarbons were not detected in the remaining soil samples. Groundwater samples were collected from SB 10 through SB 13 and submitted for laboratory analyses. Petroleum hydrocarbons were detected in the groundwater samples collected from SB 10 and SB 11. SCOPE OF WORK Planning and Permits Upon approval of this workplan and drilling locations by EHD, ATC will prepare appropriate applications to install the monitoring wells at the proposed locations shown on Figure 2. ATC will schedule field personnel and equipment, notify Underground Services Alert to locate underground utilities as required, and perform other necessary field preparation and job start-up activities. A private utility locating service will also be used to locate underground utilities that may be present in the work areas. ATC will attempt to obtain off-site access for the proposed off-site drilling locations. ATC will require authorization from off-site property owners prior to conducting drilling activities. sA22493\reports\Wkp1n_we11 inst2006.doc 3