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• Concrete Leachate Collection Barrier - A system consisting of a concrete barrier constructed, grouted, and pinned to <br />bed-rock down gradient of the impoundment, including a process water return and recycle pump, will be used to <br />collect and recycle leachate (see drawings of Exhibit E). Additionally it is worth note that the leachate water quality <br />exceeds that of the groundwater as demonstrated in 633(l)(i). <br />A network of 4" plastic corrugated perforated drain line, covered with a geo-textile filter "sock", shall be placed <br />within the impoundment spaced no more than 20' on center. This network shall be connected to the wet sump of the <br />leachate collection and recycle system. These drains facilitate a more rapid de-watering of the tailings to promote <br />quicker stabilization of the impoundment. The drains shall be placed on the interface of the impoundment with pre- <br />existing grade. The drains shall be extended up-gradient as the impoundment expands. <br />As a secondary, backup system, there shall be placed a similar network at each 20' level of the impoundment <br />elevation (corresponding to '/2 bench height). This network shall be placed venting to daylight at the impoundment <br />face. The drain ends shall be connected and piped with solid 4" plastic pipe to the wet sump of the leachate <br />collection and recycle system. <br />Diversion Ditch - Rip-rap will be installed for a channel width of 6 feet and a depth of at least 2 feet at each end of <br />the impoundment benches, at the intersection with the natural grade, to provide a permanent stormwater control. <br />This will be constructed in phases as the impoundment expands. The existence of a natural diversion channel will <br />also be acceptable for stormwater diversion as is found near the bottom half of the impoundment area. This natural <br />channel is incorporated into the sedimentation pond. This system is capable of passing a 100 year/ 24-hour storm <br />event (3.8" as reported by NOAA Atlas 2, Vol. III) For more information on stormwater management refer to <br />6.3.3(2)(c) and Exhibit T. <br />Impoundment - The disposal cell, which is an impoundment and more thoroughly described in 6.3.3(2), will be built <br />up on the down-slope face from the coarser fraction of the waste stream by hydraulic placement and hydraulic <br />• classification. A maximum of 40 square feet of new impoundment face will be formed daily. A maximum slope of <br />1.5h : Iv will be maintained at the face. This is sufficient to provide a stable impoundment embankment with the <br />proposed tailings waste stream. The finer portions of the waste stream are deposited behind the leachate collection <br />barrier and are covered in water. Sufficient clay (approximately 30% of the waste stream by weight) is deposited to <br />seal the joints and fractures in the bedrock. Exhibit E shows the details of the tailings impoundment structure. <br />6.3.3(1)0 <br />The only area subject to significant disturbance is the Tailings Impoundment. For detailed dimensions refer to <br />Exhibit E. <br />6.3.3(1)(g) <br />The access road is a public, county non-maintained road (see engineered evaluation concerning permanent man- <br />made structures in Exhibit L). Currently, the road averages 10 - 12' in width and is constructed of materials <br />developed during its construction. There is no evidence of any improvements or maintenance of this road in several <br />decades performed by the County. This roadway does not continue through to any other major road systems. <br />Occasionally, perhaps once annually depending on conditions, the operations will employ a road grader to maintain <br />the road. This could only be seen as a drastic improvement over the currently existing condition of the road. Clear <br />Creek County Road and Bridge Department publishes standards for how the maintenance is to be done. No new <br />roads are currently forecasted to be constructed. <br />6.3.3(1)(h) <br />Water for the operations is obtained from the municipal water supply of the City of Idaho Springs via a "Water Fill <br />Station Usage Permit". It is delivered to the site by hauling in a water truck and is stored in an open reservoir (as <br />described in 6.3.3(1)(e)) for use in operations. Additionally, all process water is reclaimed/recycled by the means of <br />a pontoon mounted pump or sump pump from the impoundment. <br />Water consumed by the operation consists of losses due to evaporation and interstitial water in the porous spaces <br />between the grains of waste (which is impossible to remove due to capillary pressure). Water consumption is <br />estimated at a maximum of 1,500 gallons per day by evaporation and capillary losses. Additional water of 100-200 <br />gallons per day may be used for dust control on company traveled roads. <br />4