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CSK Auto#4025 GeoTek Project No.:BC 122-4025 Tracy,California 95376 Page 7 of 20 March 2,2000 returned to the sea as the ice melted. The resulting fluctuations in sea level caused both erosion and depositional events within the Great Valley and Coastal Ranges. 3.2 VICINITY SURFACE DRAINAGE The area of the subject property is located at approximately 50 feet above mean sea level (MSL) and sloped gradually to the north at rate of about 20 feet per mile. Generally, runoff in the area of the site is directed down city streets and to storm sewers located. along Tracy Boulevard. Site specific observations regarding surface water drainage at the subject property are described in Section 5 of this report. Drainage from off-site properties was not observed to be directed onto the subject site. 3.3 GROUNDWATER Terrestrial, marine, and volcanic rocks deposited in the intermountain valleys compose Coastal Basin Aquifers (located in the area of the subject property). The intermountain basins in the coastal mountains of California are structural troughs or depressions that parallel the coastline and formed as a result of folding and faulting. Most of the folds and faults trend northwest and area result of deformation of older rocks by the intense pressures of colliding continental plates. The rocks that underlie the basins and form the surrounding mountains are primarily marine sediments and metamorphic and igneous rocks, all of which are of Mesozoic age but locally include rocks of Cenozoic age. The Coastal Basin aquifers contain fresh water located in continental deposits of sand and gravel that is usually inter-bedded with confining units of fine-grained material, such as silt and clay. The largest amount of water recharge into the Coastal Basin aquifers is from runoff of precipitation falling on the surrounding mountains and percolation of water through streambeds. It is important to note that flow through Coastal Basin aquifers is most often parallel to the long axis of the basin (because of the impermeable rocks that commonly form a barrier between the basin and the sea). According to information obtained from EDR, the depth to groundwater in the area of the subject property is anticipated to range from approximately 15 to 35 feet below ground surface. The EDR-Radius Map report also indicates groundwater flows to the north in the vicinity of the subject site.