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A McDowell &Davis Towing Phase II Groundwater,Monitoring Well Installation Report grains are angular to sub-rounded; mineralogy is arkosic with numerous grains of phologopite mica. These characteristics are typical of facies deposited in the distal portions of the Ancestral Stanislaus River alluvial fan/delta system. A clay/silt bed is encountered at 7.5 feet depth in wells MW-1, MW-2 and MW-3. The thickness of this unit varies from 5 to 10 ft. The same unit is encountered in boring B-3 at 12.5 ft. where it is 5 ft. thick. At boring B-3, a silty sand unit cut down into the clay/silt unit during depositional times. A deeper clay/silt/silt unit is encountered in boring MWA at 42.5 to 52.5 ft. This unit P Y g is also found in well MW-3 at a depth of 32.5 ft. The lower silt/clay is split in MW-3 by a 5 ft. silty sand. This unit is not found in well MW-2. In MW-2 however, an even deeper clay/silt is found at 62.5 ft. Silt/clay — clay/silt units are common in the Modesto Formation. They result , from fluctuations in the level of ice age lakes, which occupied the central portions of the Great Central Valley during the Pliestocene. Global warming episodes, which were not related to the activities of man, caused glaciers in the Sierra Nevada Range to alternately advance and retreat both into and out of the Ancestral Stanislaus River Valley. This resulted in fluctuating lake levels in the Great Central Valley during those times. Ground water level in this area was found at 60 feet in depth. 3.2 Soils Contamination Soils contamination appears to be quite limited at this site. Boring B-2 found highly contaminated soils at 15 feet in depth. At the 25 foot depth in this boring, only traces of contamination were found. At 35 feet in depth in this boring, all analytes returned ND. Borings B-1, 13-3 and B-4 penetrated clean soils. Monitor wells MW — 1, 2, and 3 also penetrated clean soils to depths of 70 plus feet. These wells were depth extensions of borings B-1, B-2 and B-4. 4.0 GROUND WATER CONDITIONS 4.1 Ground Water Flow Figure 2 is a site map, which shows the elevation of the ground water table at the site. The ground water gradient was calculated at 0.004 ft/ft in a SE direction. 4.2 Ground Water Contamination Ground waters beneath the site are contaminated with Benzene ranging from 2.2 µg/1 in MW — 3 to a high of 4.3 µg11 in MW — 1. MTBE was not detected in ground waters from this site. Other contaminates are at levels that are not a serious concern. 7