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�=:4 � �'4^r�g �'� �',t ..5^?.:. s>.f,F 3 .._f.i._. ak -. •.ix pi "�'a'"�fa..��"� Presentation and Discussion of Results. In a contour plot, a contour line represents the same elevation along a line. A closed contour therefore indicates either,a depression or a mound. The presence of closed contours representing a deep depression is an unacceptable condition in 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/waste layer is 1.8 m (6 feet), as shown on Figure EX 1, the presence of the void will create a depression 9 cm (0.3 feet) deep. This depression could trap and accumulate liquids, hindering•the free flow of leachate towards a collection point. i When the thickness of the soil/waste layer above the void is increased to 2.25 m (7.5 j feet), the depression is reduced to less than 3 cm (0.1 foot), as shown on Figure EX 2. With a 2.7 m (9 foot) thick soil/waste layer over the void, the depression disappears. The disturbance Iin the liner surface decreases as the depth to the void increases, as seen when the thickness of Ithe 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 m (3 feet) deep by 1.8 m (6 feet) long void versus liner surface grades (a) is illustrated on Figure 3. 5.0 4.0 O N 1 '0 N d � O � 0 L �2 3.0 O o � X00 U r O.O` -- (1 N 2.0 ...._. 0- (U L � O O 0 1 .0 O V) 0.0 0 5 10 15 20 25 30 35 40 Containment Liner Grade (degree) - Figure 3 Required controlled fill thickness to prevent grade reversal (T) versus containment liner grade (a) on 0.9m x 0.9m x 1.8m (3'x3'x6') void Gmsynftdcs'93-Vancouver,Canada-1505