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McDowell&Davis Towing �- Subsurface Soil Investigation +r A clay/silt bed is encountered at 7.5 feet depth in borings B-1, B-2 and B-4. 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 silt unit is encountered in boring B-2 at 42.5 ft. This unit probably `r underlies the entire site. 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. Ground water level in this area is reported at 70 feet in depth. This is well below the depths explored at this site to date. 3.2 Soils Contamination Soils contamination appears to be quite limited at this site. Boring B-2 found w 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, B-3 and B-4 penetrated clean soils. Migration of contaminates to ground water is unlikely, since the natural capillary action in the soils would tend to prevent additional downward migration. The presence of the silt unit at 42.5 ft. beneath the site would tend to form an additional barrier to downward migration. 4.0 CONCLUSIONS It appears that the contamination previously disclosed during the underground tank removal is limited to about 25 feet in depth, mostly near the fuel islands. Low levels of Lo Toluene, Xylenes, and MTBE were present in the 25 foot sample from boring B-2 and non detect in the 35 and 45 foot sample. Soil samples collected near the west end of the former underground tanks were all non detect. Groundwater has been reported in the +- immediate area at 70 feet in depth. Closure of this site can be recommended, however, new concerns regarding the properties +- of MTBE in the environment may lead to directives involving groundwater sampling. The above represents our best professional opinion as to environmental conditions at this site. These opinions were derived using data at hand, and standards of care common to the environmental consulting community in Northern California. There is the possibility that even with proper application of the above methodologies, there may exist on the subject property conditions that could not be identified within the scope of this sampling 4