1999-06-15_PERMIT FILE - M1999069

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iJ 5� EXHIBIT G WATER INFORMATION Surface Water The mine site is north of the Big Thompson River. A portion of the Big Thompson River 100 year floodplain lies within the southern portion of the east half of the permit area. The west area (Kauffman property) does not lie within the floodplain (see Exhibit Q. Since this is the outer portion of the floodplain, velocities are low. All overburden and stockpiles will be located well out of the floodplain. The operator does not claim any special benefits from water storage volume during mining operations, and will not request that the floodplain delineation be changed due to this project. There are small lakes to the west, south and east of the proposed permit boundary. These lakes are the result of mining and channel adjustments of the Big Thompson River. The topography in this area is rather gentle and slopes to the southeast. There is a natural drainageway on the north end of the site that flows to the east. The Boyd Lake outlet ditch crossses the western half of the site from north to south. Stormwater from the mining-impact areas will drain to the excavation before being pumped from the dewatering trench during the mining phase. Groundwater The excavated area will intercept the alluvial aquifer which supplies water to the Big Thompson River. The groundwater is relatively shallow in the area, only 2 or 3 feet below the original surface. The dry mining operation will be established by excavating a dewatering trench around the parameter of the excavation. Water will flow by gravity toward a collection basin. The groundwater will be pumped to either a natural drainage ditch on the northeast comer of the site, directly to the Big Thompson or to the Boyd Lake outlet ditch which discharges directly to the river on the south side of the existing permit, #M-78-327. Dewatering Effects on Adjacent Wells and Water Rights A map and tabulation of surrounding water rights and well permits are included in Attachment G1. Water rights and well permits for shallow wells which are located within 1/2 mile radius of the permit boundary are located on Exhibit G-2. The Big Thompson River is a natural hydrologic boundary, so no water rights or well permits located south of the river were identified. The pit will be dewatered during the mining phase, and some drawdown of the existing water table will occur. Several circumstances decrease the potential for injury to any of the neighboring water rights. Some of the mitigating factors are: