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l' <br /> 3 <br /> INTRODUCTION <br /> This report presents the results of a surface and subsurface hydro- <br /> logic investigation in the immediate vicinity of CF&I Steel Corporation's <br /> 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 /> Valley along the Purgatoire River about 30 miles west of Trinidad and im- <br /> mediately west of Weston, Colorado. The Allen Mine is upstream of the <br /> Maxwell Mine approximately 3.5 miles. The Allen Mine has been in production <br /> . for about 30 years and is in its declining years of production. The Maxwell <br /> Mine has more recently been put into production and coal extraction is <br /> planned for many years. <br /> The purposesof the investigations 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 /> 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 /> hydraulic and water quality parameters. These data were used to assist the <br /> t estimation of mine inflows; degree, extent and persistence of the disturbance <br /> of the piezometric surface; and potential influence of mining on the hydro- <br /> logic balance with respect to both quantity and quality of waters. <br /> GEOLOGIC SETTING <br /> 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 flows through the study area and is one of the <br /> master streams that drains the region. It heads in the Sangre de Cristo <br /> Rance south of the Spanish Peaks and has three major headwater tributaries, <br /> 1 the north, middle and south forks that unite near the study area. The study <br /> area is located slightly above 7000 feet in elevation. Cottonwood is common <br /> on the floodplain of the Purgatoire, whereas pinyon, juniper, scrub oak and <br /> mountain mahogany are common to slopes above the river. <br /> I <br /> 1 <br />