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4-2 WMU D comprises a significant portion of the area north of the South Branch of the South Fork of Littlejohn's Creek 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 a 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, D-01, and D-02 were permitted to receive designated wastes (Class II special waste). These units were constructed to meet prescriptive Class II regulatory requirements for a base liner 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 10-7 cm/sec and/or a GCL; ♦ 60 -mil high density polyethylene (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. WMUs D-93, D-94, D-95, D-97, D-98, D-99, D-00, D-01, and D-02 are inactive and can be overlain by subsequent units. WMU E is an ash fill, also known as the Eastern Ash Disposal Pit, which was constructed in 1987 to encompass approximately 4 acres and was expanded in 1992 by an additional 2 acres. It is lined with a minimum 2 -foot thick compacted clay liner and contains a blanket LCRS. A liner was placed over the northern, eastern, and western sides of WMU in 1999 and 2000 to separate the ash from designated waste that would be placed above it. It is mainly overlain by WMU D-99 and D-00, so only the south face of it is currently exposed. A final cover was placed on the southern side in 1999. WMU F North is an approximately 1 -acre leachate impoundment located just north of the South Branch of Littlejohn's Creek. WMU F North was constructed in 1999 as a double lined unit and contains a GCL overlain by a 60 -mil HDPE geomembrane, a geonet, and an additional 60 -mil HDPE geomembrane. The leachate impoundment was sized based on actual leachate generation records from 1991 to 1997 and has a design capacity of approximately 3.5 million gallons. In addition, WMU F West, constructed in 2003, is a leachate impoundment located directly west of WMU FU -03 in the northern portion of the existing landfill and has a design capacity of 3.4 million gallons. WMU F West also contains a double liner and LCRS. A third impoundment, WMU F South, is located at the southwest corner of the existing landfill, south of the South Branch of Littlejohn's Creek. WMU F South Forward Landfill SWT Engineering Joint Technical Document - April 2014 z:\projects\allied waste\forward\five year permit rvw 2013\jtd-5 yr pr 2013\text\sec 4_final.dou