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receiver and MSK radio beacon differential receiver. The GPS is reported to have sub-meter precision for horizontal location of the borings. The vertical precision is reported to be 2 to 5 times that of the horizontal precision. The GPS data were downloaded in the office and Trimble software utilized to provide differential corrections to the coordinates. All equipment utilized during the field activities was washed prior to commencement of work, and between borings to minimize the likelihood of cross-contamination between the borings. No wastes were generated during the field investigation. The shallow borings were backfilled with the soil cuttings. The two deeper borings were not cored to eliminate the generation of cuttings. Drilling and sampling procedures are presented in Appendix B. 2.2.1 Aerially Deposited Lead Investigation Fifty-five soil borings were advanced for the aerially deposited lead investigation. These borings were generally spaced approximately 30 meters (98 feet) along shoulders, in depressed areas where runoff may accumulate, and near culverts, intersections,bridge inlets, and overpasses (Figures 2 through 6). Two borings at the southwest corner of the intersection of SR120 and Austin Road were not located by this spacing. The locations for these borings (BP-1 and BP-2) were selected by Caltrans for investigation of impacts from a potential UST. The borings were advanced to a depth of approximately 0.6 meters (2 feet)below the ground surface (BGS)with samples collected from 0.1 meters, 0.3 meters, and 0.6 meters (0.3 feet, 1 foot, and 2 feet) BGS. Soil samples from the borings were collected using a 5-centimeter(2- inch) diameter sampler and transferred to zip-type plastic baggies. The soil samples were labeled,packaged, and stored on ice in an insulated chest for transport under chain-of-custody manifest to the laboratory. 2.2.2 UST Investigation 2.2.2.1 Geophysical Surveys Surface geophysical surveys were conducted to assess the presence of USTs on parcels selected by Caltrans adjacent to the intersection. The surveys were conducted on February 5, 2001,by Norcal Geophysical Consultants, Inc., of Petaluma, California. The results of the geophysical surveys are presented in Appendix C. The surveys were conducted vertical magnetic gradient (VMG) and ground-penetrating radar (GPR)methods. At parcels adjacent to the southwest and northwest corners of the intersection the approach for the geophysical surveys was to initially conduct the VMG survey to locate magnetic anomalies followed by the GPR survey to locally investigate suspect magnetic SacDP-N:IrnncjpllProjectsl82I8212641Report1120 Austin reporuloc 2-2 5/21101