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VII. Probable Hydrologic Consequences of Mining and Cumulative Hydrol The following cumulative hydrologic impact study (CRIB) has been prepared for the portion of the Purgatoire River Basin above Madrid, Colorado, pursuant to Rule 2.07.6 (2 )(c ). This CHIS assesses the projected cumulative hydrologic impacts of all anticipated mining operations in the general area of the Golden Eagle Mine. Mining operations included in the analysis include the New Elk (CMLRD Permit Number C-81-012) and Golden Eagle (CMLRD Permit Number C-81-013) mines. These mines are existing underground mines located in the Stonewall and Picketwire valleys within the Purgatoire River drainage. This assessment is based primarily upon data and analysis contained in the New Elk and Golden Eagle Mines permit applications, and upon the observations of Division personnel during inspections of the mine site. Some additional analysis was performed by the Division to complete the finding. This discussion is divided into four major subsections: Description of the Existing Environment, the Probable Fydrologic Consequences of Mining, the Cumulative Hydrologic Impacts of Mining, and Continued Monitoring Requirements. Surface and ground water are discussed separately in each subsection. DESCRIPTION OF THE EXISTING ENVIRONMENT The study area is situated in the Park Plateau, a subdivision of the Great Plains physiographic province, which consists of the dissected highlands that separate the High Plains to the east from the Rocky Mountains to the west. The Purgatoire River flows through the study area and is one of the major streams that drains the region. It forms in the Sangre de Cristo Range south of the Spanish Peaks and has three major headwater tributaries; the North For*, Middle Fork and South Fork which converge near the study area. The study area ranges in elevation from 7,000 to 9,000 feet. Cottonwood is common on the floodplain of the Purgatoire River, whereas pinyon, juniper, scrub oak and mountain mahogany are common to the upland slopes. A. Geology - The principal structural feature of the region is the Raton Basin, a broad, asymmetric synclinal basin with an axis trending north-south. The western limb is gently dipping in the study area. Steeper eastern dips are found west of the mine, outside the study area. The Raton Basin was formed during the latter phases of the Laramide Revolution when the Sangre de Cristo Range was thrust eastward. The applicant has submitted geologic maps (Map 5) and geologic cross-sections (Map 6) with the renewal application, The Golden Eagle and New Elk (dines are located on the western limb of the Raton Basin, The dip of the strata is 20 to the northeast in the general area of the mines. The coal seam at the western limit of the New Elk Mine has a dip which increases to 14 to 16 degrees, -11-