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1 1 i 1 1 Sutter Office Center Project 2267-E July 10, 2000 page 4 1 ' Older alluvial sediments of the Calaveras River and vicinity, consisting of interbedded, poorly consolidated sands and clays, underlie the subject property Boring log data from Monitoring Well U-7, located in the northeast corner of the site, indicates that 42 feet of clay overly 10 feet of sandy clay at this site The boring logs also indicate that there is no apparent hydrogeologic pathway for migration of the shallow groundwater from this site to the northeast, toward the contaminated Unocal site, see Appendix B. 1 Groundwater has been determined by the Pacific Environmental Group to flow to the northeast at a gradient of 0.01 to 0.003 at the former Unocal Service Station, located north of the subject property The shallow, contaminatedroundwater in this r g s a ea is non-potable and subject to intrusion by saline bay water. The nearest water well is located more than 1,500 feet northeast of this site ' FIELD INVESTIGATION AND SAMPLING ' Seven direct-push probes were undertaken at this site on May 22, 2000 by Vironex Environmental Field Services, at the approximate locations shown on Plate I A ' Geoprobe "5400" subsurface sampling system was used for the small diameter probes that extend to a depth of 41 feet Soil samples were obtained at 10 foot intervals, and groundwater samples were collected at the completion of drilling using 1-inch diameter ' PVC, machine perforated well screen. New PVC piping and sampling tubing was used at each probe to prevent cross contamination. The PVC pipe was removed from the probes after sampling, and the probe holes were filled with concrete The material encountered in ' the probes is presented on Plates 2-A through 2-G. Soil and groundwater samples were obtained in accordance under the LUFT requirements ' of California Water Resources Control Board The water samples were placed in 1 ' HYDRO GEO CONSULTANTS,INC