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Topography The existing environment in the general area of the Twin Pines No. 2 Mine is a semi-arid, foothill basin located on the eastern slope of the Wet Mountains. The basin, known as the Canon Ciry Coal Field, ranges in elevation from 5,500 feet near the Arkansas River to the northeast to 8,000 feet near the Wet Mountains on the west. The mine is located in the west-central portion of the coal field at an elevation of 5,800 feet. Geology Geological information is found in Section 2.04 of the permit application under the "JFSA" document heading, pages 7 through 12, and a consultant's report from Fred C. Grigsby, pages 19 through 34. Below is a summary of the geology for the Twin Pines No. 2 Mine. The mine is located along the east flank of the Wet Mountains adjacent to the axis of the north plunging Chandler Syncline. The Chandler Syncline parallels the trend of the Wet Mountain Fault to the west. The Wet Mountain Fault is comprised of pre-Cambrian granitic rocks unconformably overlying overturned sedimentary shales and sandstone units of the Cretaceous age. Strata on the northeast limb of the syncline that extend through the mine permit area dip 70 to 80 degrees to the east, forming hogback ridges. In the project area, dips of surface outcrops along the syncline vary from about 30 degrees (in the area of the sales office) to about 7 degrees (in the portal area). Three geologic rock units are of significance in the area; the Pierre Shale, Trinidad Sandstone and the Vermejo Formation. The economic coal beds that occur in the coal basin are found in the upper Cretaceous, Vermejo Formation. The coal seam mined at the Twin Pines No. 2 Mine was the Brookside seam, located 500 feet above the base of the Vermejo Formation. In ascending order, the rock units are sequenced as follows: the Pierre Shale, unconfotmably overlain by the Trinidad Sandstone, overlain by the Vermejo Formation. The Pierre Shale unit consists of 3,900 feet of olive-grey clay mixed with sandy silt layers that contain bentonite and marine fossils. It is anon-coal-bearing unit that exhibits very low hydraulic conductivity and thus is considered to be a relatively impermeable unit. At the top of the Pierre is a sequence of thin, interbedded sandstones and mudstones. The Trinidad Sandstone, duectly above the Pierre Shale, is composed of massive buff to yellow sandstones ranging from 40 to 90 feet in thickness. The unit is thick, horizontally extensive and relatively permeable. The Trinidad Sandstone unit is indicative of a prodeltaic depositional environment. This sandstone unit is the main aquifer for the region. The Vermejo Formation overlies the Trinidad Sandstone and was the coal-bearing unit of interest to the Twin Pines No. 2 Mine operation. The Vermejo consists of a complex network of mudstones, siltstones, and sandstones, interfmgered with as many as sixteen coal seams, seven of which are of economic importance. The Vermejo is indicative of a transgressive sequence, a prograding coastal lagoonal deposit intersected by deltaic erosion and depositional sediments. Thickness for the Vermejo Formation ranges from 550 to 800 feet, with an average of 700 feet in the permitted area. The Brookside coal seam is the 9