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YVATC 1117 Lone Palm Avenue, Suite B Modesto, CA 95351 www.atcassociates.com 209-579-2221 Ass 0 C I ATE s I N C . Fax 209-579-2225 Environmental, Geotechnical and Materials Engineers activities. A private utility locating service will also be used to locate underground utilities that may be present in the work areas. A drilling permit application will be completed and submitted to the San Joaquin County Environmental Health Department (SJCEHD) prior to initiation of drilling activities. ATC will attempt to obtain off-site access for the proposed off-site drilling locations. ATC will require authorization from the off-site property owner prior to conducting drilling activities. Groundwater Monitoring Well Installation Groundwater monitoring wells associated with the subject site (Figure 3) are genertoky screened in multiple zones . MWl , MW2, MW3, MW8, MW9, MW10, and MWIIR are screened from approximately 45 to 68 feet bgs and MW 13 and MW 14 are screened from approximately 45 to 60 feet bgs in the shallow groundwater zone. MW4, MW5 , MW6, and MW12 are screened from approximately 85 to 90 feet bgs in the intermediate zone. MW7 is screened from approximately 116 to 121 feet bgs and MW 15 is screened from approximately 141 to 151 feet bgs Based on recent subsurface investigation activities conducted at the site, the shallow groundwater plume appears to be adequately defined in all directions except to the south. Benzene is periodically detected in groundwater samples collected from MW3 , and MTBE and 1 ,2-DCA have always been detected in the groundwater samples collected from MW3 and MW9. These wells are located in the southern portion of the site. Monitoring wells MWl and MW8 continue to be the most impacted with respect to BTEX constituents, and MW2 and MW3 are the most impacted with respect to MTBE and 1 ,2-DCA. The intermediate groundwater plume appears to be generally defined to the northwest in the vicinities of MW12 and MW4, but not well defined in other directions. Groundwater flow in the shallow zone beneath the site tends to be somewhat variable with eastward and northward components, but generally trends northeasterly. Groundwater flow in the intermediate zone tends to be towards the south. The former Apache Plastics facility located south of the subject site across Fremont Street is a contaminated underground storage tank site and has a monitoring well network associated with environmental investigation activities conducted in response to a petroleum hydrocarbon release at that site. Based on the second quarter 2007 groundwater monitoring results associated with the Apache Plastics facility, the lateral extent of shallow groundwater contamination appears to be adequately defined to the west and south, but not to the east and southeast. The intermediate groundwater plume at the Apache Plastics facility does not appear to be completely defined towards the east and southeast. Groundwater level measurements collected during the second quarter of 2007 indicate shallow groundwater at the Apache Plastics facility flows to the east, northeast, and groundwater flow in the intermediate zone is to the south, southeast. In order to further evaluate the lateral extent of the shallow groundwater plume, two off-site monitoring wells are proposed to be installed east of the former Apache Plastic facility at the Central Valley Lift Truck located at 2080 East Fremont Street. The shallow groundwater monitoring wells are proposed to be installed east, northeast of existing Apache Plastics monitoring wells MW6 and MW 10 at the locations shown on Figure 3 . In order to further evaluate the lateral extent of the intermediate S:\Environmenta1\28349\wkp.doc 3 ATC. Associates Inc.