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5. IRRIGATION WATER <br />The Grand Junction Drainage District operates the irrigation system upstream and through the <br />project area. A major irrigation return canal was dug though the permit area many years ago by the <br />District. There are no users downstream of the United site, therefore, the sole purpose of the canal is <br />to return irrigation water to the River. The canal currently used is the Lower ditch, as shown on Map <br />C-1. A middle and upper ditch are also present, but are no[ being used. The ditches are steeply <br />incised in the flat landscape, and are approximately 12 feet deep with 1H:1 V sideslopes. These <br />ditches do have standing water for a large portion of the year. The Grand Valley Irrigation <br />Company controls the water rights in the canal system. At atl times during and after this operation, <br />the irrigation return water system will be maintained. <br />As described in the mining plan, the irrigation canal will eventually dump into the lakes, which will <br />have two discharge locations cut into the lowest lake (Area 1) which will discharge to the Colorado <br />River. This is shown on Map F. One of these locations is the trapezoidal spillway of 10' width, 2:1 <br />sideslopes, 2.5 feet depth and riprap of 8"-12" size that was used to discharge water from the <br />sediment pond during the mining phase. The spillway would simply be extended to the new lake <br />area after the pond is removed. The other discharge is installed at the north end of Lake 1 to simply <br />provide a secondary outlet. I[ will be the same size as the previously mentioned spillway and will <br />utilize 12" riprap as a lining unfit the original irrigation return drainage is reached. Both of these <br />drainages lead directly to the River. <br />15 Road Pit 10/02 39 <br />