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• There also appears to be an increase in TDS and soluble mineral components <br />in the downgradient portions. This is possibly due to increased <br />infiltration through the relatively permeable colluvial/alluvial terrace <br />deposits and subsequent discharge to the surface water system at the <br />exposed margins where local drainages intersect these deposits. Except <br />in major surface drainages with extensive contributing drainage basin <br />areas, available surface water quantities are limited and beneficial use <br />is constrained both by water availability and relatively high TSS and <br />mineral content. <br />Locations, relationships and drainage sub-basins for principle drainages <br />are shown on the Regional Hydrogeologic Map, (Map 5). <br />Identification of Surface Water Drainages. The mine and adjacent areas <br />are drained by the Magpie, Newlin and Second Alkali Creek drainage. <br />Newlin Creek is considered a perennial stream from its headwaters to the <br />• point of diversion for the City of Florence municipal water supply <br />upstream of the mine area. With diversion of essentially the entire <br />surface base flow of Newlin Creek, flows downgradient of the diversion are <br />ephemeral as are flows for Magpie and Second Alkali Creeks. <br />Magpie Creek is a relatively small ephemeral drainage with a drainage area <br />of only 2.4 square miles. The Magpie Greek headwaters are just south and <br />west of the mine area at an elevation of approximately 8,700 feet and the <br />creek flows less than three (3) miles from its headwaters to its junction <br />with Newlin Creek just downstream from the mine area. Magpie Creek <br />exhibits characteristics typical of a transitional drainage with moderate <br />flow gradients, a wide, flat channel with limited vegetation, and a base <br />consisting primarily of large unconsolidated colluvial outwash materials. <br />Within the mine area, Magpie Creek has been diverted to the southeast and <br />flows through a diversion channel designed to pass the peak flows from the <br />100-year, 24-hour storm event. The diversion channel, which was jointly <br />constructed by Dorchester and GEC discharges to the natural Magpie Creek <br />• channel just downstream from the mine area and above its junction with <br />Newlin Creek. <br />2.04.7-22 <br />