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WATER INFORMATION EXHIBIT G <br />1. SURFACE WATER GENERAL DISCUSSION <br />It is seen from Map C-1 that a slight portion of the permit area is within the 100 year floodplain of <br />the Colorado Rivet. If a 100 year flood occurs in the River, the 1929 datum shows that the water <br />level at this site will be 4457 at the western end of the permit area and 4460' at the upstream east <br />end. Using the correction of 0.99 meter to convert to the 1988 datum, the actual floodwater <br />elevation is approximately 4460' at the west end and 4463' at the east end. This level has been <br />mapped on Exhibit C-1 and should be more accurate than any regional floodplain map. The latest <br />aerial mapping from Mesa County in 2002 with a 2' contour interval has been used for the base <br />map. Since there are no structures within the mine pit area, the flood would simply be allowed to <br />enter the pit. Once the flood subsides and the water can be pumped cleanly, dewatering of the pit <br />would resume. Any storage provided by the pit would actually serve to lower the peak flow <br />downstream and possibly prevent damage to properties. <br />The lake created from the mining operation is not in any danger of being captured by the River <br />during a flood for two main reasons: <br />1) the distance to the normal bank edge of the River at its closest point to the lake is 650 feet and <br />the Interstate is located between the main river channel and the site. <br />2) this section of River is not eroding the north bank. It is a straight stretch of the River to the <br />northwest. <br />The Mine Plan section describes how surface water runoff from the site will be handled. Basically, <br />a small berm will be placed around the outside perimeter of the site to prevent any runoff from <br />exiting the site. Once excavation of the lake is started, all mnoff will enter the excavation. <br />Portable sanitation facilities will be provided to all workers at the minesite. The waste will betaken <br />off site for treatment in an approved facility. There will be no leach fields or other means of <br />sewage disposal. <br />Gilsonite Pit 10/02 23 <br />