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4-11 Is 4.4 Waste Inflow Rates For the purpose of estimating remaining site life, the estimated average annual inflow rate to the Forward Landfill over the next five years (2014 through 2018) is estimated to be approximately 1,764,000 tons, which corresponds to a weekly average inflow rate of approximately 34,000 tons. Actual quantities received may vary from these amounts. The diminishing landfill capacity for the Forward Landfill is included on Table 8. 4.5 Refuse to Cover Ratio The Forward Landfill remaining capacity and associated site life are dependent on a number of factors including the refuse -to -cover ratio. The Forward Landfill refuse -to -soil cover ratio (volume) is 4:1 (refuse to cover). Refuse -to -soil cover ratios can range from 3:1 to 5:1. The 4:1 ratio is generally accepted in the solid waste industry as an appropriate ratio for a properly operated sanitary landfill. As discussed above, Forward Landfill utilizes a number of other materials which are used as ADC, as discussed in Section 6.4.7. Typically, the Forward Landfill utilizes soil and the following ADC materials: PGM, TASW, synthetic tarps and shredded tires. Forward utilizes a refuse -to -cover ratio of 4:1 for purposes of calculating the landfill's remaining capacity and site life. In addition, the remaining waste capacity and site life are reviewed annually by Forward Landfill personnel and are required to be updated in accordance with 27 CCR, Section 21640, in conjunction with a review of the SWFP every five years. 4.6 Site Capacity As previously discussed, the permitted disposal area footprint consists of approximately 354.5 acres. The total site capacity is based on the difference between the estimated subgrade excavation and the final disposal area contours. The total remaining airspace for the Forward Landfill, as of the last aerial survey is approximately 20.2 million cubic yards (mcy) (GLA, 2013), less liner and final cover volumes. The date of last aerial survey was March 13, 2013. Using tonnage records through March 31, 2014, the remaining airspace was calculated to be approximately 20.0 mcy. Appendix F presents information regarding air space, final, intermediate and daily cover requirements and remaining refuse capacity. The remaining site life is based on a refuse to soil volume ratio of 4:1 and a refuse density of 1,588 pounds per cubic yard. Forward's consultants compare the two aerial topographic maps to estimate the volume of fill (refuse and cover soil) placed during the period between the two aerials. The site capacity calculations reflecting this information are included in Appendix F. Forward Landfill SWT Engineering Joint Technical Document - April 2014; Amended June 2014 zAprojects\allied waste\forward\five year permit rvw 2013\jtd-5 yr pr 2013\text\sec 4_finai.dou