2008-09-29_PERMIT FILE - C1981019A (6)

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RULE 2 PERMITS ........................ . 7: 1 The 1979 LRCWE report documented the absence of groundwater on the property. This report is attached in Exhibit 7, Item 1. Whereas most of the sandstones on the Colowyo Coal Company property are lenticular and interbedded with shales, the Trout Creek Sandstone is a regional geologic unit that can be mapped across the mine property and regionally. This sandstone occurs approximately 800 feet beneath the lowestmost coals to be surface mined. It is exposed to the surface north of the mine property because of the uplift in the Axial Basin. The sandstone is 75 feet thick and consists of white, fine-grained and well sorted sand, cemented with calcareous materials. The sandstone is relatively uniform across the area and can be correlated throughout most of northwestern Colorado. Unlike the sandstone above the coals to be mined on the property, the Trout Creek Sandstone is believed to contain water in storage because it occurs at an elevation beneath Goodspring Creek. However, limited data are available to describe the characteristics of the sandstone. Its recharge area is projected to be south of the mine property, or in an area where the Trout Creek Sandstone is above the elevation of Goodspring Creek and is exposed to the surface. Recharge is also expected to occur south of the mine property principally because annual precipitation increases at higher elevations. The direction of groundwater flow in the Trout Creek Sandstone is projected to be in a generally northeast direction following the general geologic structure. The principal discharge areas for the Trout Creek Sandstones are in the valleys of Goodspring and Taylor Creeks where the sandstones subcrop in the valley bottom. The Trout Creek Sandstone is removed by erosion in this general area. As a result, all groundwater in the sandstone is forced to the surface. Further evidence of the lack of groundwater above the coals currently being mined may be found by examining test hole data records collected while the property was being explored. Seventeen (17) observation wells were established to measure fluctuations in water levels at the Colowyo site prior to mining. Locations of these wells are shown on the Regional Hydrology Maps (Map 10). Depth-to-water in these wells ranged from less than 20 feet to more than 500 feet as shown in Table 2.04.7-1, Well Logs and Water Level Measurements. Four (4) of the holes were augered to a depth of 25 feet by the USGS. Three of the test holes were completed in the floodplains of Goodspring, Taylor and Wilson Creeks. The fourth test hole was completed near the west of the ridge on the east side of the mine site. The Bureau of Reclamation drilled two (2) core test holes to a depth of 200 feet; these were completed as observation wells. W. R. Grace & Co. completed seven (7) exploration core holes as observation wells. In addition to these wells, the USGS drilled four (4) test holes in the valleys of Streeter and Taylor Creeks. These holes were drilled to depths of 60 to 100 feet and none produced more than 5 gallons per minute (gpm). Of the four 25 foot augered holes completed by the USGS, the water level in No. 3 on Taylor Creek declined below the bottom on the hole in the early fall when a tributary stopped flowing, and the others showed only small water level fluctuations. The rest of the holes in bedrock showed normal water level fluctuations. Examination of the water level data indicate that some bedrock wells in the stream valleys penetrate aquifers under pressure. The wells that had not been removed by mining and could still be located were remeasured by LRCWE in 1979. The water levels in these wells had not changed significantly. In four of the W. R. Grace & Co. core holes, Nos. 27, 33, 35 and 45, water at depths of less than 100 feet was cascading from perched aquifers. In Grace core holes Nos. 33 and 35 there was no accumulation of water to depths of 280 feet and 500 feet respectively.. Similarly, in Grace No. 27 water was cascading from a depth of about 80 feet, and measurements were stable only near the plugback depth of 295 feet. Rule 2 Permits 2.04.7-3 Revision Date: 6/23/08 Revision No.: MR-91