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CVRWQCB staff requested the leachate fate and transport analyses included here in Appendix A which neglect biodegradation and focus on leachate dispersion in the CCL and vadose zone. The results of these analyses indicate that the CCL and underlying vadose zone soils provide an efficient buffer for leachate leaks, and the impacts to groundwater associated with leachate leaks would be statistically insignificant and, thus, in a real sense, would not be measurable. State regulation requires that the LCRS gravel portions of the liner also be stable against potential chemical degradation and, as a result, failure of these systems by leachate is also extremely unlikely. In addition, the system is designed to accommodate several times the peak anticipated flows calculated from detailed infiltration modeling, and the geotextile that overlies the LCRS will effectively filter out fine sediments that would otherwise enter the LCRS. As a result of the engineered redundancies in the design of the LCRS, the low volumes of leachate that are generally expected, the LCRS should function effectively throughout the operating life of the landfill and through the post -closure maintenance period. 6KIN V 01119. O 113310 911 11 IM -MIZA R 17 ® Whether or not a leak in the FML component of a composite liner system could actually carry landfill constituents into the underlying vadose zone and/or groundwater is dependant on several factors including: the volume of the leak, the chemicals that leak, the concentrations of the leaking chemicals, the distance and time of travel through the CCL element of the liner system and the dilution -attenuation characteristics of the CCL itself. 3.1 Proposed Forward Liner Design The base and slope liner systems for the future Forward Landfill are consistent with all applicable State and Federal standards and include the following elements: The base liner system is designed in accordance with 27 CCR, Section 20330 requirements for a Class 11 liner system. The base liner components for the Forward Landfill consists of: • Prepared subgrade; • A 24 -inch thick low -permeability soil (maximum permeability of 1 x 10"7 cm/sec) • A 60 -mil high density polyethylene (HDPE) liner (textured); • A 12-ounce/square yard cushion geotextile (can be omitted provided the LCRS is sub -angular to rounded); M CA2000-0487orw.rd Composite Liner V] .doc\09/19/02 Geologic Associates