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Phase I Environmental Site Assessment 2329 East Vine Street, Stockton, CA- Page 4 GPI Environmental Management property has been identified within an area of low amplification shaking and seismic hazard by the California Geological and US Geological Surveys. 3.7.2 Site Hydrology The subject property is underlain by a upper soil sequence that has been derived from the recent stream channel,overbank and terrace alluvium deposits from the Calaveras River system.The subject property is in the Lower Calaveras River hydrologic sub-basin. The regional and near-surface groundwater flow direction at the subject property would likely follow local topography to the west-northwest towards the Calaveras River located approximately 2 miles to the north-northwest. Within the recent stream channel, overbank and terrace alluvial deposits, highly permeable alluvial sands and gravels are interbedded with less permeable to impervious clayey silt units, creating a complex system of near- surface groundwater bearing zones within the upper alluvial deposits. Within a speck vertical section, movement of groundwater would be dependent upon the transmissibility coefficient of adjacent beds. The upper near-surface groundwater bearing zones when present, most likely represents perched groundwater restricted to pervious to semi-pervious sandy and sandy clay lenses and/or small channels at differing elevations. These semi-pervious zones are laterally discontinuous. Near-surface groundwater elevations and direction would also be governed by the orientation, density and thickness of the groundwater bearing semi-permeable to permeable _ soil deposits. The depth to significant near surface groundwater has been documented in three production groundwater wells within a half mile radius of the subject property to range between 40 and 100 feet below ground surface (bgs) r since 1960. Groundwater levels at the subject property would respond to groundwater pumping rates, recharge rate, and seasonal changes in precipitation. The maximum static groundwater elevations occurring between January and April, coinciding with the periods of maximum precipitation and towards the end of the hydrologic wet season. The minimum static groundwater elevation occurs towards the end of the dry season (October/November). The source of groundwater in the area is rainfall, which recharges the groundwater by infiltration and deep penetration within the near-surface soil zone and by lateral and downward percolation from the Calaveras River system through relatively more permeable soil zones.