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18 October 1995 AGE-NC Project No 95-0173 Page 2 of 5 2 3 REGIONAL GEOLOGIC SETTING The subject site is located in the eastern portion of the Great Valley geomorphic province of California The valley is a nearly flat, elongate trough trending northwest and southeast for approximately 450 miles The valley is enclosed by the igneous Sierra Nevada to the east and the sedimentary and metamorphic Coast Ranges to the west The surficial and upper several hundred feet of subsurface layers consists of a great thickness of predominantly unconsolidated alluvial and floodplain deposits(dominantly sands, silts, and clays)of Quaternary age, which are derived from the predominantly granitic mountains of the Sierra Nevada Beneath the upper sedimentary deposits he a thick sequence of marine deposits of Mesozoic age These units are further underlain by a pre- Jurassic complex of igneous and metamorphic basement rock 2 4 GROUND WATER DEPTH AND FLOW DIRECTION Ground water at the site is present at a depth of approximately 55 to 60 feet below surface grade (bsg) The uppermost ground water flows in an unconfined aquifer With depth, the aquifer becomes • more confined due to the presence of mixed heterogeneous layers of sediments The regional direction of ground water flow in the upper aquifer is generally toward the southwest 3.0. SCOPE OF WORK 3 1 DRILLING AND SAMPLING The scope of work for the proposed investigation includes advancement five soil borings to a depth of 30 feet Borings will be advanced utilizing a truck mounted, hollow stem drill ng and 8 25-inch hollow stem augers If field screening of soil samples indicated that impacted soil is present at or before a depth 30 feet, then at least three of the soil borings will be completed as 2-inch diameter ground water monitoring wells Proposed monitoring well design is depicted in Figure 3 Soils are to be described using the Unified Soil Classification System (USCS) Soil sample deucriptions avid PTS .cicreer incy results 1xM111d ISA g11mman7M nn bnnno ]no-, prepared for the final --a --o- r- r- report Cuttings generated during drilling activities will be placed on plastic sheeting and stored on-site pending nnnlutleal reSUIts R,nseate will be rontaine zed to properly labeled DOT model 17H 55- gallon drums, and stored on-site in an area inaccessible to the general public Disposal alternatives will be evaluated based on results of soil analyses Upon completion of the investigation, a report of the findings will be prepared and will include