Laserfiche WebLink
Mining activities in the area would have no impact on the overlying groundwater in the <br />Burro Canyon. Conversely, there is no indication of springs in the Burro Canyon <br />highlands immediately above the SR -13A mine site. Any groundwater in Burro Canyon <br />Formation would be restricted from recharging the mineralized zone in the Salt Wash <br />Member by the low permeable shales in the Brushy Basin Member of the Morrison <br />Formation. <br />A review of well records from the Colorado State Engineers office indicates that there are <br />numerous wells located within two miles of the SR -13A mine site. The mine is near the <br />former uranium mill tailings site that was remediated as part of the UMTRA Project <br />conducted by the DOE. Over thirty monitoring wells were installed in the river alluvium <br />to monitor the transport of contaminants associated with the uranium mill tailings. Most <br />of these wells are shallow and were completed in the saturated alluvium that is in <br />hydraulic connection with the Dolores River. There are several wells, however, that were <br />completed in the bedrock underlying the river. According to Cater (1955), the Dolores <br />River has eroded bedrock formations in areas, exposing the upper portion of the Entrada <br />Formation that is in direct hydraulic communication with the overlying saturated river <br />alluvium. Several wells in the area, ranging in depth from 150 to 202 feet, were <br />completed in the Entrada Formation. A few of the deeper wells penetrate the Navajo <br />Sandstone. Water depths in bedrock wells located in the Dolores River Valley are <br />reported to be approximately 50 feet below land surface. Several of these wells were <br />drilled in the 1950's by the Union Carbide Corporation for industrial purposes. Colorado <br />State Engineer's Office records indicate that some of these wells are capable of <br />producing up to 50 gallons per minute. <br />The well data clearly show that the upper most aquifer in the SR -13A area is the Entrada <br />Formation. Protection of this aquifer is the focus of the hydrologic analysis presented in <br />this permit. <br />In Section 35, T44N R19W, a deep well was drilled into the Wingate Formation. This <br />well is west of the Dolores River and drilled to a depth of 850 ft. According to the state <br />records, this is an artesian well. Based on this information, the Wingate is a separate <br />hydrologic system from the overlying Entrada including different areas where recharge <br />occurs for the formations. <br />With the exception of the Wingate well, there are no wells located down - gradient or to <br />the east of the SR -13A mine site. Almost all of the wells in the area, whether drilled in <br />the river alluvium or underlying bedrock, are located in the Dolores River Valley. <br />8.3.2 Hvdrostratigraphic Structure <br />The geologic structure of the area is also important in predicting the direction of <br />groundwater flow. SR -13A is located on the flank of the Disappointment Valley syncline <br />with the geologic formations dipping to the east - northeast at 0.15. Groundwater flow <br />O'Connor Design Group Inc. T - 11 <br />