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The water quality in the Northwest Intake Pool has met CDPS discharge <br /> requirements so no treatment has been required. The water quality is not <br /> expected to change so no treatment is anticipated. <br /> The North Decline gravity dewatering system is the primary dewatering system for <br /> the mine. The siphon will be maintained as a backup dewatering system. The <br /> South Portal dewatering pipe will be abandoned. <br /> As stated above the Northwest Intake Siphon has a capacity of about 220 gpm. <br /> As a backup system, it will be able to handle the majority of the flow if the North <br /> Decline gravity dewatering system requires maintenance due to decreasing flow <br /> capacity. <br /> The South Portal dewatering pipe was plugged with concrete grout. <br /> Approximately 6 cubic yards of grout was pumped into the South Portal <br /> dewatering pipe in January 2008. This should have been an adequate volume of <br /> grout to plug approximately 2,000 feet of the 4-inch pipe. However, the grouting <br /> did not achieve a complete plug of the pipe and water continued to leak at less <br /> than 1 gpm. To control the leakage, the end of the pipe was capped off and <br /> encased in approximately one (1)cubic yard of concrete. The end of the South <br /> Portal dewatering pipe was buried in the portal backfill. <br /> The french drain system explained above on page 14-7 has handled minor <br /> seepage from the mine portal seals since it was installed during 2008. The minor <br /> seepage typically evaporates and soaks into the ground before it reaches the end <br /> of the north collection ditch shown on Figure 6C. <br /> There was a heavy snowpack during the winter of 2010 to 2011. In the spring of <br /> 2011, a landowner above the mine was able to fill an irrigation pond that had not <br /> been filled since the portals had been sealed. The dip of the mine workings is <br /> about 2 to 5 degrees north 30 degrees east. The pond is located roughly south <br /> 20 degrees west of the mine portal. During late spring 2011, water from the <br /> irrigation pond percolated through the rock strata and significantly increased the <br /> flow in the french drain system. Flows varied from 2 to 15 gpm during late spring <br /> and summer of 2011. Late in 2011 the flow rate through the french drain system <br /> returned to the normal minor flow. The increase in flow rate also occurred during <br /> late spring and summer of 2012 and flow was collected in sediment Pond 9. The <br /> irrigation pond located southwest of the mine portals is believed to be solely <br /> responsible for the increase in flow rate in the french drain system. In years when <br /> the irrigation pond was dry, there was no flow increase in the french drain system. <br /> TR-63 14-30i 11/12 <br />