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Geosyntee Consultants 6 . Estimate the operation and maintenance cost of Cell 2 as an unlined C&D landfill 7 . Compare the estimated costs of the two disposal alternatives based on monthly delivery records of April 2006 through March 2007 . A summary of the first 6 steps can be found in Table 1 . Figure 2 presents a comparison of landfill disposal costs of the two alternatives. The results indicate that the economics of a particular landfill disposal method depends on the amount of C&D debris delivered for landfilling. A breakeven quantity of C&D debris was estimated from the intersection point of the two lines to be approximately 7750 ton per month. Separate C&D debris disposal in an unlined landfill is more costly to SWDD than the codisposal approach in a lined Class I landfill below the breakeven quantity (December 2006 through March 2007) and less costly above the breakeven value (April 2006 through November 2006). Figure 3 presents a cost comparison of the two landfill disposal alternatives for three projections of annual quantities of C&D debris deliveries to the landfill, calculated for 95 percent confidence limits, designated : low, average and high projections . The computations are based on SWDD records of annual landfill disposal volumes consumed by C&D debris from 1996 through 2004 and population projections (5). The projections are based on an average per capita C&D debris generation rate of 1098 pound and a standard deviation of 233 pound (see Appendix C) . The results indicate that the codisposal approach would be more cost effective for the entire period of the low projection scenario; for the first 13 year of the average projection scenario and after the first 10 year of the high projection scenario. With the high projection scenario, it is assumed that the SWDD would have to periodically increase its operating budget under the separate disposal alternative to add equipment and operating personal to handle the large increase in C&D waste stream. This analysis assumes that such budget increase would occur every sixth year at an annual rate of 20 percent. Since historical records of SWDD indicate that the quantities of C&D debris generated in the County are more likely to follow the low to average projections, the codisposal alternative where C&D debris is landfilled in a Class I facility commingled with MSW will be the less costly disposal approach for SWDD. JR70184 8 7/13/2007