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\�// 1117 Lone Palm Avenue, Suite B ',' \�/ �� Modesto, 57 -2221 www.atcassociates.com 209-579-2221 J AS SOCIATES I N C . Fax 209-579-2225 Environmental, Geotechnical and Materials Engineers MWIO, and MW11R are screened in the shallow groundwater zone at depths ranging from approximately 45 to 68 feet bgs. MW13 and MW14 are also screened in the shallow groundwater zone from approximately 45 to 60 feet bgs . MW4, MW5 , MW6, and MW12 are screened from approximately 85 to 90 feet bgs in the intermediate zone. MW7 is screened in the deeper zone from approximately 116 to 121 feet bgs. MW 15 was installed with a conductor casing to approximately 136 feet bgs and is screened from approximately 141 to 151 feet bgs. It should be noted that while slight i variations in groundwater elevations have been observed in the intermediate and deeper wells with respect to the shallow wells, there do not appear to be conclusive data to suggest that these two zones are hydraulically exclusive from the shallow zone. It is likely that different transmissive zones are present at various depths bgs which may account for variable groundwater flow direction within a single continuous water bearing zone. For purposes of this report, groundwater monitoring wells and cone penetration test (CPT) borings associated with the former Apache Plastics facility are identified by "A-" immediately preceding the identification nomenclature used by the environmental consultant, Stratus Environmental, Inc. (Stratus), retained for the former Apache Plastics ell site, Groundwaternitoring wells and=- - - borings nd=-- -borings associated with the former Apache Plastics facility referenced in this study include A-MW2, A-MW8, A-MW9, A-MWl1 , A-CPT1 and A-CPTH . A-MW2 is screened in the shallow groundwater zone from approximately 52 to 67 feet bgs. A-MW8, A-MW9, and A-MW11 are screened from approximately 95 to 109.5 feet bgs in the intermediate zone. A-CPTI and A-CPTI 1 were advanced to I ) approximately 140 feet bgs adjacent to A-MW9 and A-MWll , respectively. The locations of the referenced Apache Plastics groundwater monitoring wells and CPT borings are shown on Figure 3 . Construction details for the subject site groundwater monitoring wells and the referenced Apache Plastics groundwater monitoring wells are summarized in Table 1 . Lines of cross-sections are indicated in Figure 4. SHALLOW GROUNDWATER ZONE The laboratory analytical results of groundwater samples collected from the monitoring wells associated with the subject site in December 2006 indicate the lateral extent of petroleum impacted groundwater in the shallow zone appears to be defined in all directions except to the south. Methyl tertiary butyl ether (MTBE) was detected in the groundwater sample collected from MW3 and 1 ,2- dichloroethane (1 ,2-DCA) was detected in the groundwater samples collected from MW3 and MW9. These wells are located in the southern portion of the subject site. Monitoring wells MW 1 and MW8 in the central portion of the site continue to be the most impacted wells. The proximity of MW3 and MW9 to the southern property boundary of the subject site, dictates the need for off-site data to assist in plume definition to the south. The nearest groundwater monitoring well screened in the shallow groundwater zone south of the subject site is A-MW2. This well is located approximately 85 feet southeast of the subject site across East Fremont Street. A-MW2 is screened within the same depth interval as the shallow zone wells installed at the subject site. Review of the shallow groundwater zone monitoring well logs associated i. .I with the subject site (MMI , MW2, MW3 , MW8, MW9, MW10, MWi1R, MW13, and MW14), S:\Environmental\28349\comparative snudy.doc 3 ATC Associates Inc.