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Ms. Lori Duncan July 26, 2006 Page 4 of 6 The field assessment activities will consist of the following tasks. Geophysical Survey At the start of the field activities, BBL will perform geophysical survey activities to help identify the location of possible 550-gallon USTs reportedly abandoned in-place. The geophysical survey will be performed using the two techniques described below: An electromagnetic (EM) survey will be performed first as a rapid screening tool to identify the potential USTs and other subsurface structures. Results of the EM survey will be used to focus subsequent ground- penetrating radar (GPR) survey activities. The GPR survey will be performed to further evaluate the -- potential presence of subsurface structures. The EM survey data will be collected using vertical dipole orientation with both quadrature (apparent conductivity)and in-phase(metal sensitivity)modes. Resulting EM data will be reviewed in the field and potential USTs and underground structure locations will be marked for follow-up investigation using GPR. The GPR system transmits high-frequency electromagnetic waves into the ground and detects the energy reflected back to the surface. Energy is reflected back along boundaries or subsurface interfaces that possess different electrical properties. Reflections typically occur at lithological contacts, or changes in subsurface materials having high electrical contrasts, including metal objects such as USTs, drums, and utility pipes. These reflections are detected by an antenna and processed into an electrical signal, which can be used to create an image of the subsurface features. Potential USTs and other subsurface structures identified during the EM and GPR surveys will be marked in the field for location using GPS and/or survey. Underground Utility Line Locatine Underground Service Alert (USA) will be notified at least 48 hours before drilling activities to identify public utilities in the vicinity of the proposed borings. In conjunction with the USA, a private utility r. locating company will be utilized to further evaluate boring locations relative to underground utilities. Permittine Applicable permits will be obtained from the City of Stockton and San Joaquin County, as necessary, prior to commencing field activities. Soil Borines/Groundwater Monitoring Well Two soil borings (SB-1 and SB-2) will be to approximate depths of 50 feet bgs to the north and east of monitoring well MW-1 (Figure 1). These locations may be modified in the field based on obstructions (e.g.; overhead and/or underground utilities). Prior to beginning drilling activities, a full round of groundwater measurements will be collected from the monitoring well network to evaluate depth to water at the site. The soil boring locations will be cleared for underground utilities to a depth of 8 feet below grade using vacuum extraction system, then will be advanced using direct-push methods. Soil samples will be collected continuously at each probe location from 8 feet below grade to a depth of approximately 50 feet below grade. Each soil sample will be visually characterized (for soil type, grain size, and the presence of staining, odors, or petroleum impacts), and a portion of each sample will be placed in a container for headspace screening using a photoionization detector(PID). Up to two soil samples will be Irr JAD0006\9-8227_00261022_2006 Work Plan.doc BLASLAND, BOUCK& LEE, INC. engineers, scientists, economists