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WMU C, an approximately 4-acre Class III unit overlies the south end of Trench 4 in WMU A. Because WMU A is a Class I unit, a compacted clay dike was constructed in the north end of Trench 4 to separate the hazardous WMU A wastes from the nonhazardous WMU C wastes. WMU C contains a compacted clay liner and a dendritic LCRS. Operations began in WMU C in 1984. In 1994, the western portion of the waste in WMU C was overlain by an interface liner and blanket LCRS consisting of a geosynthetic clay liner (GCL), a 60-mil high density polyethylene (HDPE) geomembrane, and a geocomposite drainage net. Municipal solid waste and designated wastes were placed over the interface liner. Municipal solid waste was placed over the portions not underlain by an interface liner and LCRS. WMU D comprises a significant portion of the area north of the South Branch and includes several constructed WMUs. WMUs D-87, D-88 N, D-88 S, and D-89 were constructed in 1987, 1988, and 1989, respectively. All of these units met or exceeded the liner construction requirements for Class II landfills at the time they were constructed by providing at least 2-foot thick compacted clay liners. WMUs D-88 N, D-88 S, and D-89 have 4-foot thick liners. WMUs D-87, D-88 N, and D-88 S have dendritic LCRS' and D-89 has a blanket LCRS. Interface liners, as described for WMU C, have been placed over existing waste in WMUs D-88 N, D-88 S, and D-89 to separate municipal solid waste in these units from designated wastes that have been placed above them. WMUs D-93, D-94, D-95, D-97, D-98, D-99, D-00 and D-01 are permitted to receive designated wastes. These units were constructed to meet prescriptive Class II regulatory requirements for base liners and LCRS' and contain the following elements, listed from bottom to top: • Minimum 2-foot thick compacted clay liner with a maximum permeability of 1 x 10-' cm/sec and/or a GCL; • 60-mil HDPE geomembrane; • Blanket LCRS consisting of a minimum 1-foot thick layer of granular drainage material (overlain by a geotextile filter) and/or a geocomposite drainage net and a network of pipes and sumps; and • Minimum 1-foot thick protective operations layer. WMU E is the ash monofill known as the Eastern Ash Disposal Pit. This unit was constructed in 1987 to encompass approximately 4 acres and was expanded in Forward Landfill JTD 4-2 J:\Allied\Forward\JTD Amendment\March 2006 JTD-LEA Resp\JTDUTD Sec 4 Rev.doc: 05/24/02;Amendment No.1: 5/22/2006