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Composite Liner System, see Exhibit C for design details <br />and manufacturer specifications. <br />4" Perforated French <br />Drains w/ Filter Sock to <br />Leachate Collection Sump <br />6'Wx2'D <br />Perimeter Stormwater <br />Diversion Ditch <br />Slimes Fraction Average <br />Impounded Grade = 2.1 h : 1 v (25.4 °) <br />Impervious, crystalline <br />metamorphic and <br />igneous rock. <br />& Rock Backfill <br />Coarse Fraction Embankment <br />Face Grade = 1.5h : Iv (33.7°) <br />Final grade will be covered with a 6" of <br />recovered/reclaimed topsoil and /or imported <br />topsoil. This will be netted for erosion control and <br />re- vegetated. See Exhibit D for reclamation details. <br />60' 20' <br />Synteen Technical Fabrics SF350 Geogrid <br />ogrid <br />k �� , Barrier Impoundment (Drawing E5) <br />40' 1 Leachate Collection Concrete Barrier <br />_! ., I _ (see Drawing E 12) <br />-� Natural Grade <br />Avg. = 3.25h: lv <br />Tailings Impoundment Cross - Section <br />Riprap Type L, D50 = 911 <br />, <br />Depth of 18 ", Hand Placed <br />2' Depth, 1:1 <br />X i Side Slope <br />— 6' Bottom Channel Width ' X� <br />1 —� <br />Perimeter <br />Diversion Ditch <br />Scale: V = 2' <br />A trapezoidal channel with a bottom width of 6 feet, side slope of <br />1:1 and a minimum clear depth of 2 feet will be constructed at <br />each end of the impouDdment bench as it is raised, at the <br />intersection with the natural grade, to provide a permanent <br />stormwater control. Type L riprap, sized nominally with a <br />median diameter of D50 =9 inches, shall be hand placed at a depth <br />of 18 inches. Rubble and/or slightly weathered stone sorted <br />on -site from available material that meets this size specification <br />shall be acceptable for use. <br />This perimeter ditch will be constructed in phases as the <br />impoundment expands. Refer to Exhibit E Drawing E7 for the <br />Phase 1 ditch and Drawing E 10 for Phase 2 ditch. Interim <br />diversion along the projected side slope line, prior to raising an <br />impoundment bench, shall be achieved by utilizing woven <br />polypropylene sand bags (nominally 14 "x26" 50# capacity) <br />stacked two bags wide as the first course and one bag wide, <br />centered, as the second course. The sandbags shall be removed as <br />permanent riprapped channel is installed. <br />Stormwatwr & Sediment Collection <br />(see Drawing E13) <br />Composite Liner System Scale V = 50' <br />The DRMS has determined that practice based ground water protection be applied to this operation through the implementation of a composite liner system under the <br />Tailings Impoundment. <br />Venture Resources has sought the expertise of Colorado Lining International in specifying the necessary geosynthetic products suitable for this application. A three <br />component system is specified consisting of a Geosynthetic Clay Liner (Bentomat DN), overlain with a textured 60 mil HDPE Geomembrane impervious liner, overlain <br />with a GeoComposite drainage layer. Specification sheets have been included as an appendix to this Exhibit C. Additionally, extensive tailings geotechnical and interface <br />testing has been conducted and this data can be found in Exhibit C. <br />Tailings Deposition: <br />The tailings leave the flotation plant at approximately 30% pulp density via a 2 double walled HDPE pipeline that gravity feeds down to the Tailings Impoundment. The <br />concrete leachate barrier provides for the first stage starter dyke for the tailings. Directly up- gradient of the concrete leachate barrier is a small "bowl" that will be lined <br />with a composite liner. This first stage has been named the Barrier Bench and can be seen in the drawing of Exhibit E5. <br />The tailings pipeline will cross along the top of concrete leachate barrier. Valved spigots are to be spaced at 20' intervals along the pipeline facing towards the <br />impoundment. These spigots may be variably pitched downward at an angle 20 ° -45° below horizontal. The spigot discharge rate and velocity can be controlled by <br />adjusting the valve. Deposition rates and classification density can be controlled by adjusting the spigot discharge angle. <br />Using this upstream method, an embankment begins to rise as the coarse fraction segregates and is deposited most closely to the point of discharge. The slimes fraction <br />flows on past this rising embankment and forms a beach that slopes gradually downward away from the point of discharge. Process water will begin to pond at the toe of <br />the beach slope as the tailings begin to settle, drain, and consolidate. This water is recycled back to the mill utilizing pumps. Care must be taken to avoid allowing ponding <br />water to encroach too closely to the embankment face, creating a high phreatic surface condition. <br />A beach width (LB, from embankment crest to ponded water) shall be maintained to achieve a ratio of LB /h > 5, where LB is beach width and h is incremental embankment <br />lift height (typically, h = 10 feet). Considering the permeability relationships between the coarse and slimes fractions (reported by TRI in the geotechnical analysis attached <br />in the appendix), this beach length ratio will provide for adequate control of the phreatic surface. This is acceptable, according to Vick's Planning, Design, and Analysis of <br />Tailings Dams, because this is the lowest allowable limit for this upstream method of impoundment over an impermeable liner foundation. Embankment slope stability will <br />be preserved and the phreatic surface will not break out in the embankment face. <br />To further ensure impoundment stability, Synteen Technical Fabrics SF350 Geogrid shall be installed in a horizontal plane s.t 10' vertical lift spacing, except Bench #3 <br />which shall be spaced at 5' vertical lift spacing. The Geogrid shall overlap and lay over the liner system by a minimum of 12 inches. Refer to Exhibit C for specifications <br />and the factors of safety developed from this design enhancement. Additionally, a network of 4" French Drains (perforated pipe w/ filter sock) shall be installed at the liner <br />interface in the middle 1/3 of the tailings impoundment. These drains shall be spaced at `a maximum of 10' and run down the slope to collect at the leachate collection sump <br />located withing the Concrete Leachate Collection facility. The drains will be extended as the impoundment is built upwards. Having the upper end of the drain exposed <br />will allow the ability to purge the lines if they become plugged. I <br />189 <br />10 4 11 <br />°1 <br />tM <br />M <br />n <br />cz <br />o <br />rt �r <br />CS ;A <br />"I <br />� a <br />C� <br />MEMO <br />V <br />O � <br />4� <br />cri <br />o <br />� <br />o <br />N <br />� <br />h.q <br />� <br />• s <br />�,C <br />-�UA� <br />