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subsequently discharged from the pump to the sanitary sewer. This discharge water will be tested for hydrocarbon contamination. Since hydrocarbon vapors are expected to be at low levels (<300 ppm) and the solubilities of heavy hydrocarbons in water are very low, there will be little if any hydrocarbon (less than 50 ppm) in the discharge. The pump will discharge about 4 GPM of water. Vent gas treatment Activated carbon will be used to remove volatilized hydrocarbons from the vent gas. Hydrocarbon emmisions will be measured to comply with air standards agreed to with the San Joaquin Air Pollution Control District (APCD) . Inter-bed sampling will monitor the bed for hydrocarbon breakthrough, ensuring odors are not released. Spent carbon will be recycled to the supplier. The bed is sized to last for the entire test at the expected hydrocarbon level. Vacuum probes Vacuum probes will be placed surrounding the vacuum well on public property. Rough locations are shown on the test layout (Plate 3) . The probes will be used to measure the vacuum below ground which indicates to what extent the area is being influenced by the vacuum well. Eleven sets of probes will be installed (in groups of three) to profile the vacuum as it varies with depth as well as distance from the well. Each set will have probes driven to 3 , 5, and 7 feet below grade - each spaced roughly 1 foot apart from each other* - The probes (see plate 6) are 0.75-inch Schedule 80 steel pipes driven into the ground to the specified depth. A rigid drive tip prevents dirt from filling the pipe. When in place, the drive tip only will be driven further to expose the open end of the pipe to the subsurface conditions. The following installation procedure will be followed for each probe: o General procedures given earlier will be followed. o A hole roughly 6-10 inches in diameter and 10 inches deep will be excavated. A casing with a bolt down lid (irrigation valve box) will be installed flush to the ground surface. o Probes will be driven to the appropriate depth with a hand-held engine-driven hammer or similar device. The amount of time required to drive the probe each foot of depth will be recorded to indicate the relative tightness of the formation. Note: For the probes 7 feet deep in the park, a jack hammer * Note: Some sets, for example those furthest from the well, may have only the two deeper probes. 5