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Abdelwahed Facility, Ultrar e Site No. 13792 S. -O May 5, 2012 Stockton, California Work Plan Well for DPE Well Installation and Soil Gas Investigation after DPE remedial action; submit groundwater samples under chain -of - custody documentation to a California -certified analytical laboratory for analysis of total petroleum hydrocarbons as gasoline (TPHg), the volatile aromatic compounds benzene, toluene, ethylbenzene and xylenes (BTEX), and DCA utilizing Environmental Protection Agency (EPA) Method 8260B. Task 4 Monitor the DPE well for liquid -phase hydrocarbons (LPH) twice per month for approximately 2 months; collect an additional groundwater sample from the DPE well approximately 2 months after the DPE remedial action; submit the groundwater sample under chain -of -custody documentation to a California -certified analytical laboratory for analysis of TPHg, BTEX and DCA utilizing EPA Method 8260B. Task 5 Review groundwater analytical results to evaluate the effectiveness of DPE to decrease groundwater hydrocarbon concentrations. Task 6 Document field procedures, analytical results and results of evaluation of the effectiveness of DPE to decrease groundwater hydrocarbon concentrations. Proposed Soil Gas Investigation If the DPE remedial action is deemed unnecessary, the SGI shall be conducted after confirmation of groundwater conditions in the DPE well. If the DPE remedial action is completed, the SGI work shall be conducted subsequent to the DPE remedial action in order to assess the conditions that would exist after the DPE remedial action. This SGI portion of the work plan was developed in accordance with guidance contained with the California Department of Toxic Substances Control (DTSC) Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air -Interim Final dated December 15, 2004 (revised February 7, 2005), and the California Enviromnental Protection Agency (Cal EPA) Advisory Active Soil Gas Investigations dated January 28, 2003. Four soil gas sampling points (SG -1, SG -2, SG -3 and SG -4) are proposed at the locations shown on Figure 5 to evaluate the potential for vapor intrusion into current and future site buildings and soil gas conditions toward off-site areas. If the locations conflict with underground utilities, actual sampling locations may vary. Soil gas collection probes shall be advanced utilizing a direct -push rig. If advancement of the soil probes to the target depth is unsuccessful, the sample probe shall be re -advanced 3 to 5 feet from the initial location. Advancement of soil probes to target depth shall be attempted up to three times prior to abandoning the location or, depending on the refusal depth, the sample may be collected at a shallower depth. To increase the likelihood of adequate soil permeability, the soil gas investigation will not be conducted during or within one day after a significant rain event (e.g., 0.5 inch or greater). Soil gas samples shall be analyzed on site immediately after collection utilizing an on-site mobile laboratory. 1792 DPE Well WP Project No. 1792.26 5 HORIZON ENVIRONMENTAL INC.