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The need for temporary refuse storage site at <br /> each of the existing mine portals will be greatly reduced. <br /> Virtually all the refuse materials resulting from the mining <br /> operations will be transported to the surface through the rock <br /> tunnel and thence to an approved disposal site in a single operation. <br /> Most of the surplus waters that accumulate <br /> from time to time in the underground workings will be collected <br /> and discharged via the rock tunnel. Generously-sized settling <br /> ponds will assure that the final product discharged meets applicable <br /> water-quality standards. <br /> (4) Water control structures <br /> The main rock tunnel portal site is located <br /> immediately adjacent to the confluence of the south fork of Dutch <br /> Creek and the north fork of Dutch Creek--both perennial streams. <br /> Galvanized corrugated steel culvert sections are installed in <br /> both drainages. <br /> The north fork of Dutch Creek is routed <br /> through a temporary 10-foot diameter culvert designed to convey <br /> the peak flow runoff from a 100-year, 24-hour storm event. This <br /> culvert is placed in a temporary fill area which is part of the <br /> rock tunnel yard area and across which the main haul roads to the <br /> No. 1 and No. 3 mines are located. This culvert is classified as <br /> temporary because it will be removed at the cessation of mining <br /> activities unless approved for retention as part of the postmining <br /> land use plan. An arched multiplate-type culvert with a cross- <br /> sectional area of 158 square feet has been placed in the south <br /> fork of Dutch Creek to provide access to the rock disposal area. <br /> 1 37 <br />