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1.1 Landfill <br /> LF-1 is the original Foothill Landfill disposal module. This unit predated Title 27 <br /> regulatory standards and was not constructed with a base liner or a leachate collection <br /> and removal system (LCRS). The top deck area was partially-closed with an ET cover <br /> in 2006. The base elevation is estimated to be about 250 feet MSL. The maximum <br /> elevation of LF-1 is 432 feet MSL, or approximately 170 feet above surrounding grade. <br /> LF-1's exterior side slopes were graded to an average of about four horizontal to one <br /> vertical (4H:1V) with 15-foot wide benches every 50 feet along the slope. A <br /> geomembrane barrier layer was installed on the lower portion of the southern slope <br /> during the second phase of Module 1 construction. <br /> 1.2 Landfill <br /> LF-2 has an approved composite base liner system and LCRS. The first phase of Module <br /> 1 (M-IA) was constructed in 2003. M-IA consisted of a 34-acre expansion of the <br /> landfill footprint immediately south of LF-1. The second phase of Module 1 (M-1B) <br /> was constructed in 2006 and consisted of a northward extension of the landfill footprint <br /> between LF-1 and LF-2 and the filling of wastes up against the lower slopes of unlined <br /> Unit LF-1. LF-2's composite liner system consists of the following from top to bottom: <br /> 2-foot-thick soil operations layer <br /> • 8 oz./synthetic nonwoven geotextile separator/filter <br /> Drainage layer: <br /> — Base: 0.75-foot-thick gravel drainage layer with leachate collection <br /> troughs with 4-inch-diameter piping <br /> — Side slopes: geocomposite drain layer with nonwoven geotextile <br /> separator/filter <br /> • 60-mil HDPE geomembrane <br /> • Geosynthetic clay liner on prepared surface <br /> 1-foot thick prepared subgrade (base only) <br /> Foothill WQPS Rev Ldoc 1-2 <br />