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• Foundation Layer: A minimum two -foot thick layer of soil placed <br />immediately over the entire surface of the last lift of refuse. This layer shall <br />have the appropriate engineering properties, so as to provide a relatively <br />unyielding surface upon which to place and compact the low -hydraulic - <br />conductivity layer. <br />Low -Hydraulic -Conductivity Layer: A minimum one -foot thick layer of clean <br />low -hydraulic -conductivity soil containing no waste or leachate placed over <br />the foundation layer. The low -hydraulic -conductivity (or low through -flow <br />rate) soils shall be placed on top of the -foundation layer and compacted to <br />attain a hydraulic conductivity, which is the lesser of either; <br />- 1 x 10-6 cm/sec. <br />- The hydraulic conductivity of any -bottom liner system or underlying <br />natural geologic materials. <br />• Erosion Resistant Layer: A minimum one -foot thick layer of soil containing <br />no waste or leachate" placed on top of ail 'portions of1h'e Sow -hydraulic <br />conductivity layer. Vegetation root depths must not exceed the topsoil layer <br />thickness. Vegetation is to be replanted, as needed, to provide effective <br />erosion resistance. <br />The final cover should be designed to_allow for minimal maintenance. The final <br />grading design for areas flatter than 5:1 (horizontal:vertical) shall have a gradient <br />of at least three percent; to pTevent'p°onding'and-accommodate'settlement. <br />Federal Final Cover Prescriptive Design Standard <br />The minimum final cover standards for the Forward Landfill, as outlined in the <br />closure criteria of 40 CFR, Subpart F, Section 258.60jraclude: <br />• A cover with a permeability less than or equal to the hydrauli�o-conductivity of <br />any bottom liner system or natural sub -soils present, or a permeability no <br />greater than 1 x 195 cm/sec, whichever is less. The barrier layer shall consist <br />of a minimum 18 inches of earthen material. <br />• A cover which minimizes erosion of the final cover by the use of an erosion <br />resistant layer that contains a minimum six inches of earthen material and is <br />capable of sustaining native plant growth. <br />3.2.1.2 PROPOSED FINAL COVER DESIGN <br />The final cover will be designed by a registered civil engineer in accordance with <br />State and Federal regulations and will be constructed in accordance with an <br />Forward Landfill PCPCMP 3-2 <br />L:\Allied\2000.193\Reports\FinaIPCPCMP:FL-sec3: 8/20/01 BRYAN A. STIRRAT s ASSOCIATES <br />