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, Ms. Wendy Arano Project No. 809251 July 26,2000 Page 2 Before initiating field activities, IVEMCON obtained the applicable drilling permits from San Joaquin County County Public Health Services. Boring locations were marked and Underground Service Alert was notified 48 hours prior to beginning the investigation. Drilling Methods On June 15 and 16, 2000, an IT geologist observed Gregg Drilling, Inc. of Martinez, California (C-57 License No. 485165), drill three exploratory soil boring (B-1,B-2, and B-3) at the locations shown on Figure 1. Exploratory borings B-1, B-2, and B-3 were drilled to a total depths of 67 69, and 82 feet below ground surface (bgs), respectively, using 8-inch-diameter hollow-stem auger drilling equipment. Soil samples were collected at five-foot intervals to approximately 2 to 5-feet above anticipated depth of the clay layer. Continuous soil samples were then collected to total depth of the borings for purposes of assessing the distribution of the clay unit and moisture within the clay to assist in identifying the lateral extent of shallow groundwater. Borings were terminated 15 feet below the top of the clay lam proposed in the workplan. Soil cuttings were described on a boring log by the IVEMCON geologist supervising site activities utilizing the Unified Soil Classification System and American Society for Testing and Materials (ASTM) Method D-2488-90. Copies of the exploratory boring logs are presented in Appendix A. Soil samples at five foot intervals were field screened for VOCs by conducting head space analysis. Soil samples were placed in ziplock bags and sealed. A photoionization detector (PID), calibrated to an isobutylene standard was used to measure VOCs and readings were recorded on the boring log. Measured VOC readings were low, approximately 0.5 to 3 parts per million. Groundwater was not encountered in the borings and no groundwater grab samples were collected. Upon completion of drilling, the soil borings were grouted using neat cement to the surrounding surface grade. Grout was placed through tremie pipe. Subsurface Conditions Soil types encountered were consistent with those identified during previous subsurface investigations conducted at the site. Soil overlying the clay unit consisted of interbedded lenses of silty sand, silty sandy gravel, and sandy gravel. Depth to clay increased to the west ranging form approximately 50 feet at B-1, to approximately 54 feet at B-1, to ne �reon SAC:\N:\Consulring\data\Shared\Projects\PJ8\809251.aa.doc-00\ta:1 809251