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_2_ ~ <br />Excavations for rock underdrains were completed in November, 1980. <br />The drains were constructed at about the locations we recommended <br />with one exception. The southern underdrain turned south from the <br />planned location at about mid-point in the pile footprint. The <br />deviation from the planned location was to intercept a local drain- <br />age which entered the pile area at the south. We concurred with <br />the change and believe that it will result in the drain being more <br />effective. The drain excavations were backfilled using sandstones <br />developed from open pits on the Energy Fuels' mine. Photographs <br />of the drain excavations and rock backfill materials are included <br />in Appendix A. <br />The placement of excess spoil began in the disposal area after con- <br />struction of the buttress fill and underdrains had been completed. <br />The procedure for placement of excess spoil was similar to that <br />used for the construction of spoil area 2-A. Spoil was transported <br />to the desired locations in overburden trucks and dumped in loose <br />piles. The resulting piles were leveled and spread by bulldozers <br />into average lifts about 4 feet thick. Overburden trucks were <br />directed across the top of the leveled area to obtain compaction of <br />the fill. <br />Our continuous observation of construction was discontinued in <br />January, 1981, after construction of the toe buttress and under- <br />drains were completed. Since January, 1981, we have made quarterly <br />inspections of the pile in conformance with 2 CCR 407-2, Section <br />2.09.1 (11). Inspections were made in March, June and September, <br />1981. The purpose of our inspections was to observe construction <br />procedures and to examine for evidence of instabilities of the pile. <br />Materials being placed in the disposal area consisted of combinations <br />of sandstone and clays tone. The placement procedure was similar to <br />that previously described. Lift thickness varied between 3 and 6 <br />feet, but averaged about 4 feet. Photographs of the types of mate- <br />rials being placed and the placement procedure are included with <br />this letter. <br />Outslopes of the fill appeared to be about 2.5:1 (horizontal to <br />vertical). The lowest outslope of the pile was about 3: 1. Vertical <br />distances between benches was about 50 feet. It appears that the <br />excess spoil pile is being constructed in general conformance with <br />our recommendations presented in our Job No. 5664 B. No areas of <br />instability were evident during our inspections. It appears that <br />the spoil pile is stable at this time. <br />