Laserfiche WebLink
<br />Description of the Environment <br />General Area <br />The Lorencito Canyon mine is situated near the center of the Raton Basin, southeast of the town <br />of Weston, Colorado. The County Map Topographic Series, Las Animas County, Colorado, <br />sheet 4 of 7, published by the Uni[ed States Geological Survey, depicts the greater mine area. <br />Lands in this azea are a small part of the larger Pazk Plateau, a portion of the Great Plains <br />physiographic province, consisting of dissected highlands that separate the High Plains to the east <br />from the Rocky Mountains to the west. <br />The major structural feature of the region of the mine area is the Raton Basin, a broad, <br />asymmetric synclinal basin with its axis trending north-south. Rock units deposited during the <br />Cretaceous period of the Mesozoic Era and during the Paleocene period of the Cenozoic Era are <br />exposed throughout the basin due to uplift and subsequent erosion. Coal seams in the Vermejo <br />Formation and the Raton Formation are exposed at various locations throughout the basin. Coal <br />Honing is no newcomer to the region, as mining has been conducted since the 1850's, mostly in <br />underground mines faced-up into coal seam outcrops in the valleys. Coal quality is generally <br />very good, with a low sulfur conteat and good coking qualities in many of the seams. Due to <br />parting and splits in the seams, much of the coal mined in the region requires washing prior to <br />loadout and shipment. <br />The Purgatoire River flows through the area and is the major stream which drains the region. Its <br />headwaters are in the Sangre de Cristo mountain range to the west and the Spanish Peaks to the <br />northwest. The North Fork of the Purgatoire drains the Spanish Peaks area, the Middle Fork <br />drains the area west of Stonewall, Colorado, and the South Fork of the Purgatoire drains the areas <br />south of Highway 12 into New Mexico ro the south. The Purgatoire River drains 404 square <br />miles above its confluence with Lorencito Canyon. The United States Geological Survey <br />(USGS) has operated two stream gaging stations in the vicinity; site 07124050 at Stonewall, <br />Colorado and site 07124200 at Madrid, Colorado. The Stonewall site drains 57 square miles and <br />the Madrid site, abor•e Trinidad Reservoir, drains 505 square miles. Numerous perennial, <br />intermittent, and ephemeral streams drain to the Purgatoire between these two sites. <br />Surface water quality is acalcium-sodium bicarbonate water, neutral to slightly alkaline ,and a <br />low hardness. pH ranges from 6.15 to 8.8 and Total Dissolved Solids (TDS) ranges from 50-650 <br />mg/1. <br />Ground water occurrence in the region can best be described as limited. Consolidated bedrock <br />aquifers generally have a low hydraulic conductivity and a low storativity, rendering bedrock <br />aquifers unusable for sources of economic water. Alluvial groundwater is present in the major <br />alluvial valleys of the region and is used for domestic purposes associated with ranching <br />activities. <br />Ground water quality is variable, but can generally be described as fair quality. Alluvial water <br />use is suitable for most uses, where TDS levels are not elevated. Bedrock water quality is fair <br />io <br />