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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2014-0006 -22- <br />FORWARD INC. AND REPUBLIC SERVICES INC. <br />FORWARD CLASS II LANDFILL <br />SAN JOAQUIN COUNTY <br /> <br /> <br />LANDFILL CLOSURE <br />91. Title 27, section 21090 provides the minimum prescriptive final cover components for landfills <br />consisting of, in ascending order, the following layers: <br />a. Two-foot soil foundation layer. <br />b. One-foot soil low flow-hydraulic conductivity layer, less than 1x10-6 cm/s or equal to <br />the hydraulic conductivity of any bottom liner system. <br />c. Geomembrane layer (this layer is required for composite-lined landfills for equivalency <br />to bottom liner). <br />d. One-foot soil erosion resistant/vegetative layer. <br />92. Title 27 allows engineered alternative final covers provided the alternative design will provide <br />a correspondingly low flow-through rate throughout the post-closure maintenance period. <br />93. The Discharger submitted a December 2008, Preliminary Closure and Postclosure <br />Maintenance Plan (Appendix L in the Joint Technical Document) for closure and post-closure <br />maintenance of all the unlined and composite-lined landfill units at the facility. The Closure <br />Plan proposes eight-staged closure projects over the life of the Landfill. Final closure dates <br />for the various stages will depend on module fill rates. The first closure Stage consists of <br />most of the top deck, north and west side-slopes of the Austin Road Unit and the east, west <br />and south slide-slopes to a height of 150 feet of the Forward Unit. To date, the first stage <br />areas on the Austin Road Unit have a final cover installed but not yet certified as closed. All <br />of the first stage was tentatively scheduled for completion by December 2014. <br />94. Due to Forward Landfill changing development plans, the 2008, Preliminary Closure and <br />Postclosure Maintenance Plan, is outdated and it is unlikely that the 2008 closure stages can <br />occur as projected. This Order requires submittal of an updated Preliminary Closure and <br />Postclosure Maintenance Plan. <br />95. The Discharger proposes an ET final cover for closure of the landfill. The proposed final <br />cover consists of a minimum of one-foot of existing interim cover overlain by a minimum of <br />three-feet of selected fine grained soil. <br />96. From 2006 to 2010, the Discharger completed a demonstration project for an alternative final <br />cover system on the northern slope of the Austin Road Unit. The project involved a three- <br />foot thick soil cover over the existing one-foot thick interim cover. The soils consisted of on- <br />site clayey silt with an as-built minimum hydraulic conductivity of 1 X 10-6 cm/sec. <br />Performance of the demonstration cover was monitored for climate (rainfall, evaporation, <br />solar radiation, relative humidity, barometric pressure, temperature and wind speed) and soil <br />moisture at various depths within the 4-feet thick cover. Lysimeters at the bottom of the <br />cover system measured no breakthrough (no water infiltration through the cover and into the <br />waste) over the four-year test. Soil moisture and heat dissipation sensors installed at various <br />depths within the cover demonstrated overall soil drying trends; upward moisture and soil