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l' 3 <br /> <br />I! This report presents the results of a surface and subsurface hydro- <br />logic investigation in the immediate vicinity of CFBI Steel Corporation's <br />1 Maxwell and Allen Mines in Las Animas County in southern Colorado. Both <br />mines are underground coal mines with entries located in the Picketwire <br />11 Valley along the Purgatoire River about 30 miles west of Trinidad and im- <br />mediately west of Heston, Colorado. The Allen Mtne is upstream of the <br />Maxwell Mine approximately 3.5 miles. The Allen Mine has been in production <br />1~ for about 30 vears and is in its declining years of production. The Maxwell <br />Mine has more recently peen put into production and coal extraction is <br />~~ planned for many years.; <br />1~ The purposes of thelnvestigations reported herein were to gather and <br /> analyze the hydrologic ,. water quality, and selected geologic data pertinent <br />~ to the application for a mining permit. Because of the expected phase out, <br />1. the~item of major concern at the Allen Mine is the effect of the active <br /> waste dump upon the quality of waters in the adjacent Purgatoire River, <br />~~ and this concern is analyzed in detail. The study at the Maxwell Mine in- <br /> cluded characterization~of the bedrock and alluvial deposits relative to <br />II hydraulic and water quality parameters. These data were used to assist the <br /> estimation of mine inflows; degree, extent and persistence of the disturbance <br />i of the piezometric surface; and potential influence of mining on the hydro- <br />I iogic balance with respect to both quantity and quality of waters. <br />' <br />II GEOLOGIC SETTING <br />Il The study area is situated in the Park Plateau, a subidivision of the <br /> Great Plains physiographic province which is applied to dissected highlands <br /> that separate the High Plains to the east from the Rocky Mountains to the <br />' west. The Purgatoire River flaws through the study area and is one of the <br /> master streams that drains the region. It heads 1n the Sangre de Cristo <br />I Range south of the Spanish Peaks and has three major headwater tributaries, <br /> the north, middle and south forks that unite near the study area. The study <br />II area is located slightly above 7000 feet in elevation. Cottonwood is common <br />'`~ <br />1 on the floodplain of the Purgatoire, whereas pinyon, ,juniper, scrub oak and <br />/ I <br />I <br />mountain mahogany are common to slopes above the river. <br />