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Pre-Design Investigation Workplan Former Manufactured Gas Plant—Lodi, California 3.0 PROPOSED SCOPE OF INVESTIGATION ACTIVITIES The purpose of this pre-design investigation is to provide the additional data necessary for design, planning and permitting of the Site remedy. While the RI completed at the Site is adequate for the purpose of preparing a human health risk assessment, feasibility study, and removal action Workplan, the proposed pre-design investigation will provide additional data to facilitate design and planning of the removal action and further refine the proposed excavation limits presented in the Draft Final RAW to minimize changes to the limits of excavation during remedial excavation activities. Specifically,the proposed scope of work for the pre-design investigation is as follows: • Geotechnical observation, sampling and testing will be conducted at approximately 7 to 12 borings and 13 to 20 trenches at various locations in areas proposed for excavation in the Draft Final RAW. Initially, geotechnical borings will be placed in the general areas of proposed borings PB-6, PB-10, PB-11, PB-32, PB-56, PB-57 and PB-59 (Figure 4). Targeted trench locations are also shown on Figure 4. Geotechnical borings will be advanced to depths ranging between 25 and 60 feet. Trenches will be advanced to depths ranging between 2 feet and approximately 5 feet. Based on actual field conditions encountered and the observations of the Soils Engineer's representative, the location and depths of proposed borings and trenches may be modified in the field, and additional locations may be advanced. • Collection of additional soil samples at various locations throughout the Site to further refine localized areas of impact for the purpose of planning soil handling activities during remediation. As shown on Table 1 and Figure 4, soil samples to be collected from locations PB-1 through PB-65 will be analyzed for one or more of the following analytical test methods: o PAHs using EPA Methods 8270 SIM ; o Benzene, toluene, ethylbenzene and total xylenes (BTEX) using EPA Method 5035/8260B; o Extractable total petroleum hydrocarbons (IPH-e) quantified as diesel (TPHd) and motor oil (TPHmo) using EPA Method 8015M; o Purgeable total petroleum hydrocarbons (TPH-p) quantifield as gasoline (TPHg) using EPA Method 5035/8260B; o California Assessment Manual (CAM) 17 Metals using EPA Methods 6010B/7471; o Lead using EPA Method 6010B. • Collection of additional soil gas data at proposed locations SG-7 through SG-14, as shown on Table 1 and Figure 4, to facilitate remediation planning and further refine the lateral extent of potential soil vapor in areas not targeted for remediation. Temporary soil vapor probes will be installed at depths of 5 and 15 feet bgs as TERRA PACIFIC GROUP Page 9 April 4, 2012