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Abdelwahed Facility, UltraWSite No. 13792 V May 5, 2012 Stockton, California Work Plan Well for DPE Well Installation and Soil Gas Investigation Task 5 Document the over-drilling activities, well replacement installation, and groundwater sampling data. Contingent DPE Work Plan The scope of work for the contingent DPE remedial action will be developed on the basis of the tasks outlined below. It may be appropriate to refine this scope of work or to cancel the DPE remedial action on the basis of groundwater analytical results from the MW -1 replacement well. The purpose of the DPE remedial action, if necessary, would be to extract impacted groundwater and, in the process, locally draw down the water table and extract adsorbed volatile hydrocarbons from exposed sub -water table soil. The DPE method utilizes high -vacuum blower, capable of generating up to approximately 25 inches of mercury (Hg) vacuum, connected to a "stinger" hose inserted into the well with the end of the set below the water table to extract groundwater and soil vapor. The stinger hose is sealed off from the atmosphere at the well head to concentrate vacuum on the well screen and the adjacent subsurface. Water and vapor are extracted, separated, treated and discharged at the surface. Groundwater analytical samples collected before and after pilot testing will provide data for evaluation of the effectiveness of DPE to reduce dissolved hydrocarbon concentrations in groundwater. Groundwater sampling will be conducted in accordance with the enclosed Horizon Field Methods and Procedures. The following tasks are proposed to complete the DPE remedial action: Task I Select a contractor to provide a truck -mounted DPE services; notify the San Joaquin Valley Air Pollution Control District (APCD) of the proposed DPE pilot testing and obtain permit, if necessary; obtain water discharge permit from the local sanitary sewer department; and Update the site-specific Health and Safety Plan to include issues related to the proposed DPE work. Task 2 Collect depth -to -water (DTW) measurements from all site wells prior to initiating and prior to terminating DPE pilot test; and utilize existing groundwater monitoring data or collect a groundwater sample from the DPE well prior to DPE remedial action. Task 3 Conduct up to 5 days of DPE pilot testing on the new DPE well; measure and record vacuum, vapor flow and hydrocarbon concentration readings, and volume of extracted groundwater hourly for the first 4 hours of DPE operation, and every 4 hours for the duration of the pilot test; treat, as necessary, and discharge vapors directly to the atmosphere and groundwater to the sanitary sewer; depending on water discharge requirements, treat extracted groundwater through a sediment filter and granular -activated carbon prior to discharge to the sanitary sewer system; if necessary, temporarily store treated groundwater in an above -ground storage tank (3,000 to 6,000 gallons capacity); if necessary, sample stored water for discharge analytical characterization; collect a groundwater sample from DPE well immediately 1792 DPE Well WP Project No. 1792.26 4 HORIZON ENVIRONMENTAL INC.