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And V!W� 2ujQm.qf JkMILI, In a contour plot elevation along a line. A closed . contour Eine.represents the same contour therefore indicates either a depression or a mound The pr=nco of closed contours representing a deep depression is an unacceptable condition fi, the design of a liner system. The deformed surface -elevations in each grid point are calculated by the computer program. The deformed surface contours on the 7 percent sloping surface are then plotted for each case, as shown on Figures EX—1 - EX 4. Where the thickness-of the soil/wastc layer is 1.8 m (6 feet), as shown on Figure EX 1, the Presence of the void will create a depression 9 cm (06 feet) deep. This depression could trap and accumulate liquids, hindering the free flow of leachate- towards a collection point. When the thickness of the soil/waste Layer above the void is increased to-2.25 in (7.5 feet), the depression is reduced to less than 3 cm (0.1 foot); as shown on Figure EX 2. With a 2.7 in (9 foot) thick soil/waste layer over the void, the depression disappears. The disturbance in the liner surface decreases as the depth to the void increases, as seen when the thickness of the soil/waste layer is increased to 3.6 m (12 feet) (Figure EX 3 and EX_4). To evaluate the potential for grade reversal, a characteristic curve of required soil/waste thicknesses M over a 0.9 m (3 feet) wide by 0.9 in (3 feet) deep by 1.8 m (6 feet) long void versus liner surface grades (a) is illustrated on Figure 3. 5.0 E EZ H4.0 0 -0 0 0 -0 3.0 '0 C -C 0 V- L) 0 1! 2 OO 0- � 0 0 0 1 .0 Q: 0 0 0.0 0 5 10 15 9*20 25 30 35 40 Confoinment Liner Grade (degree) Figure 3 Required controlled fill thickness to prevent grade reversal (1) Vversus containment liner grade (a) on 0.9m x 0.9m x 1-8m (3'x3'x6') void Gtosynftdr-s93-Vancouver,Canada-1303