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<br />ditches. Discharge of ground water is into the St. Vrain and the South Branch. At <br />times of low ground water conditions the St. Vrain may be rechazging the ground water. <br />Western Mobile has installed a ground water monitoring system in the areas of <br />current and future mining. The system consists of 27 piezometers installed in the <br />alluvium and staff gauges in irrigation ditches, ponds, and the St. Vrain. Water level <br />elevations are measured monthly in the piezometers and at staff gauges. The locations of <br />the various monitoring stations aze shown on the "surface features" map that is part of <br />this document. Hydrographs for piezometers and staff gauges are presented in <br />Appendix C. Ground water quality is monitored quarterly from five of the piezometers. <br />Western Mobile's hydrologic monitoring system has been installed to obtain <br />baseline information on the water table, ground water quality, and surface water - <br />ground water relationship, and to monitor possible future impacts due to mining. <br />In order to ensure that the proposed mining does not adversely impact the <br />prevailing hydrologic balance in the vicinity of the Lyons site, Western Mobile will <br />utilize two mitigation techniques. The first of these is the slurry wall. The company <br />recently employed the slurry wall technique at the Lyons operation in order to create <br />a sealed water storage reservoir from one of the previously excavated mining stages on <br />the Rockin' WP-North parcel. <br />Slurry walls are subsurface, nonstructural walls that act as barriers to the lateral <br />flow of ground water. These cutoff walls are constructed using the slurry trench <br />technique and are composed primarily of soil and bentonite, a natural clay mineral. <br />Western Mobile's use of this technique at the Lyon's site has been successfully <br />demonstrated and will be used to mitigate ground water impacts due to mining. <br />The second ground water mitigation method that Western Mobile will employ at <br />the Lyons site is the compaction of backfilled slopes. This method has been <br />successfully employed by the company and other sand and gravel producers who <br />needed to seal off excavated areas from ground water infiltration. <br />Over the life of the Lyons mining operation it will be necessary to relocate and/or <br />remove two irrigation ditches that are used to irrigate the Lyons site, including the <br />Goss Private #l, Montgomery private ditch, and the several laterals off the Smead <br />ditch. Owners of water rights in the area will not be adversely impacted as a result of <br />the contemplated ditch relocations and/or removals. <br />The state engineer's records were reseazched in order to identify all registered <br />wells within 500 feet of the Lyons project. There are a number of domestic wells in <br />the vicinity of the proposed project area. These are shallow alluvial wells that do not <br />Western Mobile Lyons - Rockin' WP G-5 <br />