2012-10-01_REVISION - M1977305 (16)

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Factors of geology, geochemistry and arid climatic conditions have combined to form the Uravan Mineral Belt - dominantly sandstone deposits of uranium, vanadium and associated metals. These same conditions restrict the movement of these minerals into the environment. The only viable transport mechanism for the migration of these minerals from ore deposits located deep in geologic formations to possible exposure in the environment is via a groundwater pathway. 8.3 Regional Groundwater To understand possible exposure routes resulting from mining, the geology that forms the framework for the movement of groundwater needs to be understood. 8.3.1 Area Aquifers According the Geologic Quadrangle for the area (Cater et al., 1955), there are two mapped springs in the area within two miles of the mine site. Horsethief Spring, located to the west, is mapped in the Burro Canyon Formation. Recent field observations located the spring in a small side canyon located below massive sandstone /pebble conglomerate blocks at the contact of shale units. These shale units could be within the Burro Canyon Formation but the location of the spring near the base of a small side canyon, at a lower elevation than indicated on the map, suggests that the shales of the Brushy Basin Member of the Morrison Formation are restricting the downward movement of groundwater resulting in the discharge of water into the spring. It is difficult to estimate discharge quantities since the spring is characterized by small seepage areas with several phreatophytes such as willows and aspen trees, and cattails surrounding a small pond. Field surveys were unable to locate the unnamed spring but the mapped location suggests a similar hydrologic situation where groundwater from the Burro Canyon Formation encounters the impermeable shales of the Brushy Basin and discharge along incised canyon walls. The Burro Canyon Formation in the Long Park area consists of isolated erosional remnants of resistant sandstone and pebble conglomerates that form highlands containing native species such as oak brush and ponderosa pine trees that require additional amounts of water compared to the typical pinyon - juniper sagebrush areas. Large areas of exposed sandstone along the top of the highland areas provide access for precipitation to collect in depressions and infiltrate into the bedrock. Compared to the available recharge areas along canyon walls, the Burro Canyon highlands provide a significant increase in the area available for recharge of the limited amount of precipitation. Mining activities in the area would have no impact on the overlying groundwater in the Burro Canyon. Conversely, there is no indication of springs in the Burro Canyon highlands immediately above the LP -21 mine site. Any groundwater in Burro Canyon Formation would be restricted from recharging the mineralized zone in the Salt Wash Member by the low permeable shales in the Brushy Basin Member of the Morrison Formation. O'Connor Design Group Inc. U - 10