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4.3 Field Investigation The scope of work for this project includes an underground utility location survey and the advancement of up to 6 soil borings using direct-push sampling equipment. The utility surveys will be conducted using an electromagnetic metal detector, ground-penetrating radar(GPR), and radiofrequency survey equipment. 4.3.1 Underground Utility Location Survey An underground utility location survey will be conducted to assess the absence or presence of unreported underground utilities at the site. The geophysical surveys will clear utilities for the direct push boring locations. The surveys will be conducted using a high sensitivity metal detector(EM-61) with a 1 by 1- meter coil, ground-penetrating radar (GPR), and radio frequency survey equipment. The approach for the geophysical surveys will be to initially conduct an EM-61 survey to locate anomalies followed by the GPR survey to locally investigate suspect magnetic anomalies. Electromagnetic radio frequency pipe locating equipment will be used to investigate possible underground utilities. NThe EM-61 survey will be conducted using nodes spaced approximately 0.8 meters (2.5 feet) apart. The data will be reduced in the field and a contour map produced that is referenced to aboveground structures that may affect the results. The EM-61 should be able to detect ferrous and non-ferrous metallic objects. EM-61 anomalies potentially created by a utility will be investigated using GPR. The GPR traverses will be spaced approximately 1.5 meters (5 feet) apart and oriented both parallel and perpendicular to the anomaly. A map showing GPR traverses and subsurface features located by the GPR will be produced. Based on the GPR survey results, electromagnetic radio frequency pipe locating equipment will be used to investigate possible underground utilities. 4.3.2 Drilling and Soil Sampling Up to 6 soil borings will be advanced using direct-push sampling equipment. Soil borings will be located in accordance with Caltrans' Task Order 10-OA7401-ME. Figure 2 shows proposed boring locations. Soil borings will be advanced to first encountered groundwater, which is expected to be encountered at approximately 10 meters (32 feet) below ground surface (BGS). Soil samples will be field screened using a flame ionization detector(FID) and a photo- ionization detector (PID). Approximately 7 soil samples will be collected from each boring. Discreet soil samples will be collected at 1.3-meter(4-foot) intervals until groundwater is SAC/DP-N:bancfp"rojects1 M34760�wWn&hsp\SR 120 wp.doc 4-2 WPM