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Permit M77-424 Amendment 1 <br />Exhibit D <br />Page 3 of 6 <br />was constructed; several manhole access vaults and siphon vaults exceed I S feet in depth <br />in this area within 2,400 feet of the evaporation pond inlet. Details of the pipeline <br />construction are shown on Sheet 8 of Exhibit D. <br />Evaporation Pond <br />The construction details of the evaporation pond are shown on Sheet 2 of Exhibit D. The <br />pond system consists of an overflow spilling pond {initial settling pond) and the main <br />evaporation pond. The pond design incorporates a leak detection system comprised of <br />gravel under-drains and 2-inch perforated PVC pipe connected to a collection and <br />inspection vault. High density polyethylene {HDPE) liners were installed in both ponds; <br />the settling pond was constructed with a 100 mil liner and the evaporation pond was <br />constructed with 80 mil liner. <br />The bottom of the settling pond measures approximately 80 feet long by 10 feet wide <br />with a total exposed liner footprint of approximately 140 feet long by 70 feet wide. The <br />bottom of the evaporation pond measures 393 feet long by 393 feet wide, the high water <br />line footprint measures approximately 417 feet long by 417 feet wide, and the exposed <br />liner footprint is approximately 453 feet long by 453 feet wide. As shown in Sheet 6 of <br />Exhibit D, the construction design of the evaporation pond includes an 8-foot high <br />wildlife security fence that surrounds the pond site. The estimated total disturbed area for <br />the initial settling pond and evaporation pond includes the area within the wildlife <br />security fence, an area of 10.0 acres. <br />Surface stormwater diversion structures including small diversion ditches and channels <br />were constructed along the evaporation pond access road to divert stormwater from the <br />road and pond. Sheet 2 of Exhibit Dshows arun-on ditch feature that was constructed on <br />the hillslope above and to the northeast of the pond. <br />D) The size of areas to be worked at any one time. <br />The construction schedule is not considered relevant for this amendment because <br />construction of the water transmission pipeline and evaporation pond was conducted in <br />1984 and no documentation of construction schedules is available. It is assumed that <br />several hundred feet of water transmission pipeline was constructed at any one time, and <br />the entire evaporation pond area was constructed within a 6-month period. <br />E) Approximate timetable to describe mining operation. <br />The timetable associated with initial mine development is presented in the original mine <br />permit M77-424 as required in the regulations and rules at that time. The timetable <br />associated with construction of the water transmission pipeline and evaporation pond <br />(this amendment) is not relevant to this amendment as the facilities have already been <br />constructed. It is assumed that construction of the pipeline and pond took place <br />simultaneously. Because the final grade overlying the pipeline matches the surrounding <br />