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-5- c s i` 2. The surface of the proposed waste embankment area should be ' graded to develop a low zone which will perform <is a sump in ;' " the center of the disposal area. Moisture which collects on the refuse will flow rapidly through the relatively permeable refuse and collect on,the surface of the hard bedrock which will occur throughout the disposal area. ~3. A gravel drain system should be constructed in the sump area. We anticipate the sump area to consist of a site approximately 100 feet in diameter about 2 to 3 feet below the surrounding area. The entire surrounding disposal area should drain toward the sump. All existing sand and gravel should be stripped to provide a direct impermeable barrier below the entire disposal site. ~4. An 6-inch perforated drain pipe,'cjonstructed with either clay drain pipe, open-joint tile, or a"durable plastic drain material, should be installed from the bottom of the sump and should lead in a southerly direction to a point of discharge in the area of the existing sediment pond. The drain line should be bedded in coarse, washed gravel. The entire sump area should be backfilled with the clean, on-site sands and gravels. ~;5. After the sump area has been constructed, the refuse should be deposited in dump piles by truck methods. On a periodic basis .:zthe piles should be spread in approximately horizontal layers, `- y~rolled and compacted to a minimum of 90 percent of the maximum dry density determined using AASHTO Method 7-99. The presently planned rate of production indicates that approximately 1.7 feet of fill will be developed during the early years of use. As time pro- gresses and the refuse pile increases in height, the surface area will reduce and the increase in height will be such that 2 to 2.5 feet of fill may be produced on an annual basis. ~o. In order to meet the requirements for compaction, we suggest that the refuse be piled in piles and compacted on approximately a 6-month basis. This will preclude the possibility of developing excessively thick layers for compaction. At the time of compaction, it will be relatively simple to make density tests to determine compliance with the required density. This would result in an inspection of the pile approximately each months o operation. 7. No samples of the materials for construction of the pile were available at the time of this investigation. We have conducted analyses of stability of numerous waste disposal areas for large mine wastes constructed out of the. overburden materials in the surrounding areas. Based on these investigations, as well as observation of performance of waste piles, indicates that the