SR 06:208 - Laserfiche WebLink

whether soil meets the physical and chemical criteria for Prime rarmland or Farmland of Statewide Importance. Fannlands arc further discussed under Agriculture and Grazing below. Soil Types for Groundwater Recharre '!1,e majority of groundwater recharge derives from stream recha'l~e through gravelly streambeds across the valley floor. Zone 7 recharges groundwater by releasing water into streambeds with high percolation rates and in Lake I of the Chain of L~ke with its gravelly western shore. Soil Supports Stmctures Buildings need stable soils for support. DurinI' seismic activity. some soil types are not as capable of supporting stmctures as other soil types. Ground motions during earthcluakes arc related mainly to local soil conditions. Local soil conditions and subsurface geologic characteristics arc two of the six major components - including magnitude and distance - related to structural damage from an earthquake. In addition. where loose granular sands arc present. soils tend to compact resulting in soillicjuefaction and settlement. 9 Landslides and soil erosion arc also related to surface and subsurface soil characteristics. Soil type is just one of numerous factors that contribute to landslides including slope steepness. aspect'" rainfall. rock type. land use. distance (roln fault. distance [tOOl water sources and vegetative cover. See the Public Safety Element for a discussion of geologic hazards alonv with l'oals policies and programs related to geologic safety. Water Resources II Croundwatef Pleasanton lies within the Alameda Creek watershed, a drainage basin encompassing about 675 s'luare miles between Mount Hamilton and Mount Diablo. Alameda Creek, the principal stream, flows from its origin on Mount IIamilton until it meets the Arroyo de la l.aguna near Sunol and then nllls west through Niles Canyon to San rrancisco Bay. 'lbe Arroyo de la Laguna collects the surface water mnoff from the ,\rn"tlor Li, ElI..ore Tt1 Valley and carries it south to Alameda Creek. 11,e General Plan Map designates these creeks along with other areas as Public Health and Safety with a Wildlands Overlay Although all of the creeks feeding the Arroyo de la Laguna arc naturally seasonal, Zone 7 of the Alameda County Flood Control and \Vater Conservation District releases controlled amountj of both stored water from the Del Valle Reservoir and imported water from the South Bay Allueduct into ') Seed, H. Bolton, Department of Civil Engineering, University of California, Berkeley and I.M. ldriss, \Voouward-Clyde Consultants, Ground Ala/iolls anti Soil Liquefacliol1 J)urin~~ Earthquakes, Earthquake Engineering Institute, Berkeley, California, 1982. In Aspect of a slope is exposure to a particular direction. 11 Zone 7 Water Agency, Stream Almlagemm/ Alaster Pkm, March 2006. Con os Ekmcnl, CC 082906, redlinc VII-9