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GROUND WATER INVESTIGATION WORK PLAN BULK TERMINALS SITE, PORT OF STOCKTON, STOCKTON, CALIFORNIA concentrate. Borings C-1, C-2, C-3, C-4, C-5, and well MW-3 are presumed downgradient from copper transfer and/or conveyor system transport areas. Upgradient and Downgradient Ground Water Sampling Borings C-2 and C-5 are also located to characterize ground water quality presumed downgradient from the site. Borings C-6 and C-9 are located to provide presumed upgradient ground water samples. After sampling ground water from the first sandy aquifer materials, these borings will be drilled to approximately 50 to 60 feet bgs to obtain ground water samples from the next underlying coarse-grained aquifer material (the "B" water-bearing zone) to evaluate vertical extent of chemicals in ground water. 3.1.2.2 Boring Advancement Borings will be advanced using hydraulic direct-push equipment to the first significant water- bearing zone, estimated to be no more than approximately 30 feet bgs; the actual boring depths will be determined in the field. A relatively permeable geologic unit is anticipated to be at least two feet thick and to consist predominantly of sand or silty sand. Silt and clay layers are not interpreted to represent significant water-bearing units. Borings C-2, C-5, C-6, and C-9, will also be advanced to the underlying layer of coarse-grained water-bearing materials of at least two-foot thickness underlying the sandy aquifer, anticipated to be no more than approximately 50 feet to 60 feet bgs. Boreholes will be advanced sequentially into each of the geologic materials: surficial silty materials, underlying clay, and lower silty to sandy materials to the sandy water-bearing zone. Proposed soil samples will be collected in the borehole prior to advancing to the next underlying geologic layer, terminating with collection of ground water grab samples from the sandy water-bearing zone. To maintain sample integrity, dual-tube drilling equipment will be utilized for all borings. This method entails setting the outer tube of the dual-tube system to prevent mixing of water or sediments from above in the underlying material being sampled. Once the outer tube is set, the inner tube is extended to facilitate a sample of the deeper material and associated water. If water continues to enter the borehole, indicating that an adequate seal between water bearing units cannot be achieved, then separate boreholes may be advanced to enable collection of a representative water sample. 3.1.2.3 Water Level Measurements The depth to water encountered in each boring will be measured to the nearest 0.01 feet using an electric water level probe. Observations of both the depth to saturation and the depth to the potentiometric or water table surface will be recorded. Repeated measurements will be made July 2005 Page 10 Environmental Risk Services Corp.