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b) Filter Building <br />See discussion below on Chemical Handling Systems and Containment. <br />c) Thickener <br />The thickener is 26 feet in diameter and 8 feet deep. The total height of the thickener from the ground is 15 <br />feet. The volume of the thickener is a maximum of 4400 cubic feet of slurry. The concrete containment is bigger <br />than the thickener itself and will handle a minimum of 110% of the full volume of the thickener. The thickener <br />has a 6 inch thick reinforced concrete containment, as shown on Map 1. <br />Based on the footprint area of 1693 sq. ft, as measured from the site inspection and using a minimum wall <br />height of 3.0 feet, this results in a containment volume of 5079 cu. ft. Since there is approximately 200 cu. ft. of <br />structures in the containment, the actual volume of containment is 5079 — 200 = 4879 cu. ft, which is 111% of <br />the tank volume. The plans correspond to the designs presented in TR -05. The plan view of the foundation <br />shown on Map 1. <br />In the case of a rupture of the thickener tank or piping, a slurry pump is located at the low point of the thickener <br />containment, which would then pump the slurry back to the 18000 gallon tailings tank located in the filter <br />building. See Map 1. In this way, no tailings will be allowed to leave the area, although by the time that the <br />tailings enter the thickener, they will be inert anyway. Therefore, with this system, there is actually triple <br />containment of the tailings slurry at the thickener. These are 1) the tank itself, 2) the concrete secondary <br />containment and 3) the sediment pond capture system. <br />The slurry will be transported from the filter building to the thickener by overhead HDPE process water lines of <br />8" diameter. A return slurry line for concentrated slurry and a return waterline is installed on the bridge. The <br />bridge will consist of a steel truss structure of 6 feet width and 100 feet long. An air line and electric cable is also <br />suspended in the same bridge. The bridge is 18 feet high to allow clearance and all support structures are shown <br />on Map TH-1 of the permit. As seen on this Map, there will be two support structures; one at the filter building <br />end of the overhead truss and the other at the thickener end, and the distance between them is 100 feet. The <br />truss supports at both ends will be steel supports in a foundation which is separate from both the thickener and <br />the filter building, as shown on the revised TH drawings in the permit. <br />Revenue Mill Certification Page 14 of 20 <br />