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Lorencito Canyon Mine (C-1996-084) <br />Geology, Soils, and Topography <br />MT- 04 <br />The major structural feature in the region of the mine area is the Raton Basin, a broad, asymmetric <br />synclinal basin with its axis trending north -south. Rock units deposited during the Cretaceous period <br />of the Mesozoic Era and during the Paleocene period of the Cenozoic Era are exposed throughout the <br />basin due to uplift and subsequent erosion. Coal seams in the Vermejo Formation and the Raton <br />Formation are exposed at various locations throughout the basin. <br />Soils in the permit area are thin, and in places, non-existent. The exception is the valley bottoms, <br />where soils are moderately well developed. Clay loam, with a low infiltration rate, describes the <br />majority of soils in the area. <br />Elevations within the permit area range from approximately 6,750 feet above mean sea level in the <br />northeast part of the permit area to approximately 7,250 feet in portions of the southwestern permit <br />area. Steep slopes and rugged canyons generally describe the topography of the permit area. V- <br />shaped drainages are rimmed by steep, rocky outcrops, and watersheds are divided by narrow, sharp <br />ridges. <br />Surface Water. Groundwater. Water Usage. and Water Rights <br />The Purgatoire River flows through the region of the mine area and is the major stream that drains <br />the region. Its headwaters are in the Sangre de Cristo mountain range to the west and the Spanish <br />Peaks to the northwest. The North Fork of the Purgatoire drains the area west of the Spanish Peaks, <br />the Middle Fork drains the area west of Stonewall, Colorado, and the South Fork of the Purgatoire <br />drains the areas south of Colorado Highway 12 into New Mexico to the south. The Purgatoire River <br />drains 404 square miles above its confluence with Lorencito Canyon. The United States Geological <br />Survey (USGS) has operated two stream gauging stations in the vicinity: site 07124050 at Stonewall, <br />Colorado and site 07124200 at Madrid, Colorado. The Stonewall site drains 57 square miles, and the <br />Madrid site, above Trinidad Reservoir, drains 505 square miles. Numerous perennial, intermittent, <br />and ephemeral streams drain to the Purgatoire between these two sites. <br />In addition to the two main drainages near the permit area, Lorencito and Cow creeks, numerous <br />other drainages exist within the permit and adjacent area. Chimney, Jeff, Puertecito, Little Pine, <br />Bonita, Alamosa, and Little Alamosa creeks all drain areas within the permit and adjacent area. Only <br />Lorencito Creek demonstrated perennial flows during the baseline collection period; minimum flows <br />at all other sites were recorded as zero at least once during the baseline period. Large flows occur in <br />ephemeral drainages in response to intense precipitation events, typically during the months of July, <br />August, and September. Snowmelt contributes only a small percentage of total runoff, as infiltration, <br />evaporation, and sublimation likely account for most of available snowmelt waters. <br />Page 5 of 10 <br />