2016-08-08_REVISION - M1980244 (2)

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Primary containment In the leach circuit at the HGM, the vat leach tanks are considered primary containment. To ensure that overtopping of the primary containment does not occur again Newmont has implemented critical changes and proposes to make another. First,within the circuit of six vat leach tanks a series of"upcomers"were replaced with"downcomers". Downcomers are a series of pipes used to convey process slurry from one tank to another. Downcomers deliver the slurry to the base of the interior of the tank, as opposed to upcomers which moved slurry to the top of each tank. Second, the diameter of the pipes that convey the slurry was increased from 8 inch to 20 inch. With this change,the process slurry was able to flow more easily from tank to tank given the expected available head pressure. Figure 1 shows the comparison of process slurry movement between upcomers and downcomers in the vat leach tanks. Additionally,Newmont proposes to replace the conditioning tank with a simple process slurry delivery line to the vat leach tanks. In each of the afore mentioned improvements the primary containment has been enhanced and the potential for an upset condition to occur has been greatly reduced. JFE — — t —r--t— r r—-----a--- �---t— 1 1 -NW.IL eatr—1 th' I I I I I IT— I E wsu'—r� III 11 � I R ! II I I I I I 1 1 1 I II r- .II i II I I 1 1 1 i II I II 1 ' II '1 11 I I 1 1 I 111 II1 ( I !I ! 1110-47-056 -647-054 1 1 11 11 1 I I I I 1110 111 1 I I Figure 1:Representation of 3 vat leach tanks.Red arrows indicate flow direction of the process slurry with previous upcomer conveyance. Green arrows indicate flow direction of the process slurry with current downcomer conveyance. Each tank is understood to contain mixers shown in the far left tank. Source:FL Smidth,HighGrade Mill Leach Area General Arrangement Sections,Drawing#20-647-32,Issued for construction 02-25-2013 Secondary containment In the leach circuit at the HGM, the concrete curbing surrounding the vat leach tanks is considered secondary containment. Per Amendment 10,Volume 1, Exhibit U, Section 6.3.2, "The leach tank secondary containment will hold 75%of the volume of one tank.". Any leaks or spills occurring on the secondary containment are designed to be collected by a sump and recirculated to the vat leach tanks. In the event of an upset condition within the vat leach tank circuit,the process slurry would be removed from secondary containment within seven days of the event. Tertiary containment At the HGM,the 80 mil textured Linear low-density polyethylene (LLDPE) geomembrane liner beneath the entire facility is considered tertiary containment. Figure 2 shows the original design