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Therefore, South Portal discharge capacity was increased through the <br />installation of a pipe from the No.2 South Mains sump to outfall 001. The <br />routing of this "South Portal" 4-inch diameter pipe is presented on Figure <br />t4-6. The capacity of this discharge pipe is about 75 - 100 gpm. See <br />Figure 14-6 Roadside South Portal Mine Water Discharge System and <br />Figure 14-7 Roadside South Portal Dewatering Schematic. <br />The Northwest Intake Pool (see Figure 14-7) must be maintained between <br />elevation 4755 and 4762 to assure the siphon continues to function. The <br />level of the pool is measured through monitoring well N-1 which is located <br />at the reclaimed North Decline. This 7-foot elevation range equates to <br />about 2.3 million gallons per foot or about 16.1 million gallons (ref. AHR <br />Table M-3). The discharge from the siphon is increased or decreased, by <br />adjusting a valve, depending on water level measurements in well N-1. <br />Changes in the elevation of the Northwest Intake Pool are gradual <br />because each foot of increase or decrease represents 2.3 million gallons. <br />The operator considers the combination of the siphon and the South <br />Portal dewatering pipe to be an effective mine water discharge system for <br />.. the South Portal. However, this mine dewatering system does require a <br />high level of monitoring and some periodic maintenance. <br />An alternative plan has been developed which should be virtually <br />monitoring and maintenance free. The operator has identified a location <br />where an angled hole can be drilled into the mine. Once this hole is <br />completed, water will flow by gravity from the mine. This plan is presented <br />on Figure 14-8 Mine Dewatering -Plan and Profile. This new "North <br />Decline" mine dewatering pipe will be 8-inches in diameter and will have a <br />flow capacity of 350 gpm (see figure 14-10). <br />After this new North Decline gravity dewatering system is installed, it will <br />become the primary dewatering system for the mine. The siphon and <br />South Portal dewatering pipe will be maintained and monitored in <br />accordance with permit requirements until the gravity dewatering system <br />is fully and adequately functional. The siphon and South Portal <br />dewatering pipe will then be considered backup systems. <br />14-30 (Rev. 1 /26/01) <br />~,,t~,4.....,. r 3 <br />