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9 6.3 Additional Site Controls <br />It is important to understand that the geomebrane, the composite liner system, and the <br />LCRS are only components of an extensive and integrated environmental control and <br />monitoring system at the site. These and other environmental control systems provide <br />redundant and complementary protection and monitoring for the proposed landfill. <br />Discussion of additional site controls that are integral to the overall performance of the <br />system is presented below. <br />Operations Layer and First Lift of Refuse - While it is anticipated that all of the <br />composite liner system components will be constructed in strict accordance with the <br />project plans and specifications and will be monitored under stringent CQA protocols, <br />any post construction damage can be detrimental to the containment characteristics of the <br />finished system. In order to provide protection to the composite liner, one foot of select <br />operations layer soils will be placed over the LCRS geotextile and the first layer of refuse <br />will consist of select waste that excludes large angular particles capable of puncturing the <br />system. During this waste placement operation, landfill inspectors will monitor waste <br />placement and will identify and exclude materials that could potentially be a threat to the <br />liner. An additional benefit of the Forward site is the ready availability of relatively fine- <br />grained soils for use in the protective/operations layer. The general lack of large angular <br />particles minimizes the risk of puncture and distress to the FML. <br />Leachate Management - Leachate collected in the LCRS will flow through the drainage <br />i layer to the pipes and subsequently into leachate collection sumps. Submersible pumps <br />! located in each sump will pump leachate into a force main located outside the lined <br />landfill area. The force main will discharge to lined surface impoundments in which the <br />leachate will evaporate. Three leachate evaporation impoundments are currently planned <br />for the site. The leachate impoundments are intended to serve as a primary mechanism <br />for disposal of collected leachate. However, the impoundments may be supplemented by <br />other disposal methods during peak years of operation, if necessary. Leachate in excess <br />of the impoundment's capacity will either be pumped to temporary on-site tanks or <br />trucked for off-site disposal. <br />11 <br />Leachate Chemistry Trends - Class IFIII landfills are prohibited from accepting known <br />hazardous wastes. This has greatly reduced the inflow of hazardous chemicals into the <br />municipal solid waste stream, and the results are evident in the leachate chemistry data <br />obtained from more modern facilities. In addition, studies conducted on the chemical <br />composition of landfill leachates suggest that leachate chemistry is the most problematic <br />during the operating life of the site and within one to two years after the site closure <br />(Tchobanoglous, et. al., 1993 and McBean, et. al., 1995). Shortly thereafter, chemical <br />concentrations in leachate typically decrease, often dramatically. In fact, an analysis of <br />leachate quality by Tchobanoglous, et. al., 1993 compared the quality of leachate from <br />new landfills (less than two years old) with the quality of leachate from mature landfills <br />(greater than ten years old), and concluded that leachate quality improves substantially <br />over time, with concentrations of individual constituents decreasing by factors of 10 to <br />100 over that eight year time span. Similar observations have been made at lined <br />C:\2000-048\Forwsrd Composite Liner V3 .doe109/19/02 <br />ffm <br />Geologic Associates <br />