ARCHIVED REPORTS_2013 - Laserfiche WebLink

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' Corral Hollow LFG System Audit and Upgrade Report performance goals of Title 27 as an accepted engineered cover system. The work was completed ' in 2013. The Site's total closure area is approximately 45 acres now that this additional closure is complete. ' Surrounding Land Use The adjacent and surrounding land uses are compatible with CHLF. Land uses within one mile ' of the Site include transportation (Interstate 580) to the north, grazing to the south, agriculture, low density housing, and transportation(Interstate 580)to the east, and grazing to the west. ' Land within 1,000 feet of the Site is zoned as General Agriculture (GA). There are no occupied residences or structures located within 1,000 feet of the existing disposal footprint. The nearest occupied residence is located approximately 1.8 miles north-northeast from the Site's permitted ' disposal boundary. A recent groundwater well survey conducted by the County indicated that there is one active public (Well# 21), two active industrial (Well# 22 and #25), and one active irrigation(Well# 12) supply wells within one mile of the Facility (RWQCB, Sept. 2013). Site Vadose Zone Geology and Hydrology Past drilling and geologic investigations at the Site suggest that the landfill is underlain by recent alluvium, Quaternary stream terrace deposits, and relatively unconsolidated sedimentary rock of the Plio-Pleistocene age Turlock Formation. Lithology within these three units is similar, and includes assemblages of clays, silts, sands, and gravels. The Corcoran Clay member of the ' Corcoran Formation (also referred to as the Turlock Formation) has been identified in exploratory boreholes drilled around the northern third of the landfill. The Corcoran Formation is characterized as moderately to high plastic clays, and mixtures of clays with silts, sands, and ' gravels (RWQCB, 2013). The first encountered groundwater ranges from about 12 feet to 65 feet below the native ground ' surface. This shallow perched aquifer is found beneath the northeast and east side of the landfill property. This aquifer is not found west of the landfill. Groundwater elevations range from about 228 feet MSL to 237 feet MSL. The direction of shallow perched groundwater flow varies due to ' groundwater mounding at groundwater monitoring well SB-1. However, there are indications of shallow groundwater flowing northeasterly from the Site due to groundwater elevation monitoring in wells MW-9A through MW-11A located offsite. The estimated average gradient ' of the shallow aquifer is approximately 0.02 feet per foot. The estimated average groundwater velocity is 5.6 feet per year(CB&I, 2013). ' The existing groundwater monitoring system includes seven wells screened in the shallow, perched aquifer on the eastern side of the landfill. These wells are identified as SB-1, MW-4, MW-5, MW-8, MW-9A, MW-10A, and MW-I IA. MW-9A through MW-11A were installed in ' 2012 as evaluation monitoring wells to determine the extent of off-property shallow groundwater impacts. Two replacement deep aquifer wells MW-6 and MW-7 are installed at 385 and 330 feet bgs respectively. 3 December 2013 1