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3 <br /> 1 <br /> I <br /> EWE <br /> V <br /> -.a Fite No.2070.2 <br /> 19 Dccember 199t <br /> Page 2 <br /> of 39 feet for MW-2 and a d -,th of 35 feet for MW-3. <br /> HSE determined the direction of groundwater flow(groundwater gradient) beneath the subject site <br /> =w by utilizing hydrostatic water level measurements obtained following completion of the initial three <br /> monitoring wells. However, due to the near linear placement of the three monitoring 'wells relative <br /> to one another, an inaccurate determination of the groundwater gradient was calculated. <br /> Anderson Consulting Group (formerly Anderson Geotechnical Consultants, Inc.) was retained by <br /> Anheuser-Busch Companies in January 1988 to install two,additional monitoring wells and further <br /> assess the extent of potential groundwater conutminadon. In February 1988, Anheuser-Busch <br /> instructed Anderson Consulting Group (ACG) 'lo perform the completion of the groundwater <br /> contamination investigation as well as compose a Problem Assessment Report for the site. <br /> In September 1989,both the eastern-most tank of the tank cluster as well as the single tank located <br /> in the front parking lot of the bakery were excavated and removed. Three soil samples were <br /> obtained by another consultant following removal of the tanks. One soil sample (AA-1563) was <br /> obtained from beneath the product line which ran from the eastern tank of the tank -cluster to the <br /> dispenser. The other two samples (AA-1561 and AA-1562) were obtained from each end of the <br /> eastern tank of the tank cluster. Laboratory analysis of the soil.samples indicated the presence of <br /> 609 parts per million total petroleum hydrocarbons for sample AA-1563. . No petroleum <br /> hydrocarbons were detected in the other two samples. Soil samples were not obtained from the <br /> tank excavation near the front of the bakery.+' r' <br /> 1.3 Geologic and Hydrogeologic Setting <br /> The Fainbo Bakery site is located in the north-central portion of the geomorphic province known <br /> as the Central Valley. The Central Valley is bounded by the Coast Ranges to the: west and the <br /> lled <br /> Sierra Nevada to the east. Material derived from erosion of the adjacent mountains; has epo the <br /> d <br /> valley with up to several thousands of feet of consolidated and unconsolidated sedimF3ntary deposits, <br /> These deposits overlay older, Mesozoic (_IOD-200 million years old) granitic basement rock. The <br /> sedimentary deposits of the valley thin out to severai feet in thickness both westward and eastward <br /> near the bases of the Coast Ranges and the Sierra Nevada, respectively. <br /> The subject property is situated directly atop Holocene (C 10,000 years old) Basin deposits which <br /> formed in response to erosional and transpyrtational processes of the San Joaquin River and its <br /> tributaries (Department of Water Resources, 1974). The thicknesses of the Holocene deposits vary <br /> from approximately 5 feet near the edges of the Central Valley to several huWred feet in the <br /> center of the valley (United States Geological Survey, 1985). These deposits are generally <br /> horizontal layers of uncirlsm--Tidated, fine-grained sand, silt and clay which grade basin-ward into <br /> nrgani: mu4. <br /> 7 a Holocene Basin k"r sr tits are underlain by Pleistocene (up to 2 million years old) alluvium, <br /> Formations of alWvf%i deposits are stratigraphically present in the vicinity of the subject <br /> i propetty (United States Geok;"I-al Survey,1985). '1"3'+cse formations are, in order of increasing age, <br /> the Modesto Formation, RKerhank Formalion and Turlock Lake Formation. All three formations <br /> ' were deposited as stream channel and/or overbank deposits in response to fluvial processes. Du.: <br /> i <br /> f ` n AND£ASON i <br /> CONSULTING . <br /> ` f GROUP <br />