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1 <br /> sediments range in geologic age from Jurassic (205 million years before present) to Holocene <br /> ' (present time) and include both marine and continental rocks and deposits (Page, 1989) <br /> The project site is located on older alluvium, of Pleistocene and Holocene age. It consists of <br /> interbedded zones of gravel, sand, silt and clay, with some hardpan. The older alluvium ranges <br /> in thickness from about 0 to 400 feet in the Ripon area <br /> ' The regional water table beneath the site lies at approximately 50 feet below grade and flows <br /> northerly based on San Joaquin Flood Control and Conservation District data. The only surface <br /> ' water bodies within one-half mile of the site are irrigation canals. <br /> 3.0 INVESTIGATION <br /> 3.1 Phase 1 Activities <br /> On September 11, 1990, WaterWork personnel advanced one soil boring (MW1) to <br /> approximately 65 feet below grade at the project site to accomplish the following 1) further <br /> define the vertical extent of petroleum hydrocarbon soil contamination; 2) determine soil <br /> stratigraphy, and 3) install a groundwater monitoring well within the uppermost aquifer in order <br /> to assess groundwater quality The boring/well location is plotted in Figure 3. <br /> ' 3.1.1 Soil Sampling <br /> Drilling was conducted by Spectrum Exploration (C57 license #512289) using a hollow <br /> stem auger drill ng. An experienced field geologist was present to continuously log all <br /> ' drill cuttings and soil samples utilizing the Unified Soil Classification System <br /> Descriptions of soil types encountered, sample collection intervals, boring abandonment, <br /> ' and well construction details were recorded on well/boring Iogs (Appendix I). Cored <br /> soil samples were collected above the water table at five foot intervals and below the <br /> water table at select intervals in accordance with RESNA's Soil Sampling Protocol <br /> (Appendix Il) Soil samples from 40 and 45 feet below grade were submitted for <br /> laboratory analysis Analysis was conducted for benzene, toluene, ethylbenzene, xylenes <br /> ' R-OM92 TIL 3 <br />