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Page 2 April 4, 1989 This operation plan does not change the design or the intent of these ditches; it simply provides procedures for refuse placement that will be implemented [o avoid drainage problems during construction. Once a 50 feet refuse lift has been placed, side collection ditches will be graded to the final configuration in that portion and erosion protection material will be installed as previously described in the permit. Concern over maintaining adequate drainage exist during construction az the refuse is actually being placed. First, it is very difficult during placement of material to maintain a consistent downgrade in the side collection ditches. The dozers and other heavy equipment move large volumes of material in each cycle and only one 6 inch rise in a small area can cause minor ponding during a rainfall event. Figures 1 and 2 show a placement procedure that should eliminate the this concern. By placing an initial material thickness of approximately 4 feet (2-2 foot lifts for compaction) in the furthest uphill location, material can then he placed in subsequent downhill locations as shown. An appreciable downgrade (5%-12%) will also be maintained from the upper end of refuse placement to the outslope face. Crowning of the embankment has been designed for 3% to 5% from the middle to either side for the final configuration. During construction, a sleeper crowning may be maintained. This crowning could be from 5% to 12%, which will help eliminate water running down the outslope face. These steps mill maintain a constant drop in the side collection ditches and over the entire refuse placement area, thus eliminating ponding during construction. The second construction concern is that of undisturbed area runoff entering the refuse placement area during lift construction. This problem can be avoided by establishing the ditch outline during construction at the juncture of original ground and the refuse. As shown in Figure 3(a), each subsequent 2 foot lift continually re-establishes the ditch configuration. With the exception of the long bench reach, [he side collection ditches have been designed as triangular channels with 3H:1V sideslopes and a 2.75 feet depth. Allowance in this depth has been made for 1 foot of freeboard. Due to the steep grade of the embankment outslope, the channels are lined µ~th gabion blankets of 9 inch thickness to resist erosion. The design ditch cross-sectional area is 22.7 fee[. As the refuse is placed during construction, the ditch will be established with one side in the original ground and the other side in the refuse, as shown in Figure 3(a). Since i[ is difficult to establish an exact 3H:IV grade during construction, it is therefore specified that, during refuse placement, the side collection ditches of the current working area will be constructed in an approximate triangular form and will have a cross-sectional area of at least ?3 square feet. This area is adequate to pass the 100-year 24-hour maximum design flow of 99 cLs. The construction portion of the side collection ditches will not be protected for erosion control due to the temporary nature of the ditches. WFC will maintain the flow lines of [here ditches as the refuse is being placed. This will include a check at the end of each shift to insure that the Oow lines are open and the gown and downgrade are in a positive flow condition. In addition, the side collection ditches will be checked at least once per week to assure that the necessary cross-sectional area is maintained [o pass the design event described above.