You have been charged with design of a liner to be used in a cell for a solid waste landfill in Virginia. The cell you will be designing is approximately square and covers 10 hectares. New regulations in the state permit a performance-based design under provisions of RCRA Subtitle D. According to these regulations, two liner systems, an earthen liner and a composite liner, were proposed. The earthen liner includes a 60 cm clay liner compacted in 4 lifts, whereas the proposed composite liner consists of a 60 mil HDPE geomembrane placed on the CCL. In the first phase of the study, the engineer managing the project requested that the toxicologists and hydrogeologists working for her determine an acceptable mass loading to the aquifer, which underlies the new cell. Two contaminants of concern were chloride (Cl- ) and dichloromethane (methylene chloride). The analysis showed that the mass loading for chloride cannot exceed 250 tons/year within 100 years. For methylene chloride, the maximum permissible mass loading is 2kg/year for 100 years. Samples from the leachate collection system in an existing cell suggest that the typical concentration for chloride is 1,500 mg/l. For methylene chloride, the typical concentration is 1.5 mg/l. The effective diffusion coefficient for chloride and methylene chloride are 1 x 10-9 m2 /sec and 5 x 10-10 m2 /sec, respectively. The aqueous concentration percent of solubility of the methylene chloride is 90% with the HDPE geomembrane. A soil resource survey by your company indicates that clay available on site is suitable for constructing a clay liner. Laboratory tests show that the clay has a Gs of 2.7 and can be compacted to achieve hydraulic conductivity of 1 x 10-7 cm/sec. All of the laboratory specimens were compacted at a water content of 24.8% and a dry unit weight of 15.8 kN/m3 . The specimens were essentially saturated as compacted. Also previous studies have shown that, for these soils, the effective porosity is typically 80% of the total porosity and the organic carbon content is typically 1%. Regulations in the state require that the depth of leachate on the liner be maintained at a depth of  0.3 m. Develop the mass loading (flux times area of the cell) versus time plots for the chloride and methylene chloride (for CCL as well as composite liner system). Estimate the mass loading at 100 years (in kg/year) by developing a spreadsheet solution. Check your calculations with those presented by Shackelford (1990) charts where applicable. Use intervals of 10 years for your plot. Which of the liner systems (CCL versus composite) should be used for this design? Discuss your solution and defend your analysis. For the geomembrane/CCL composite liner system, determine the mass loading at the base of the liner and assume a circular defect in the geomembrane along with three different types of contacts, perfect, good, and poor contact. Assume a clay hydraulic conductivity of 1 x 10-7 cm/sec for all cases. Use Foose et al. (1999) solution for the case in which diffusion is dominant.