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occur from May to late June with moderate pocks, large volumes, and long flow duration. <br />Avezage flow is 345 cubic feet per second (cfs) with a range of 12 to 6,690 efs. The San Miguel <br />flows are influenced by upstream diversions, storage, and irrigation <br />Principal tributaries to the San Miguel River in the vicinity of Uravan include Spring, Atkinson, <br />Tabeguache, and Hieroglyphic Creeks. Tabeguachc Creek is perennial. The other streams are <br />generally dry and flow in response to rain events. Peak flows occur most frequently in spring and <br />summer. <br />4.6 Uses of Adjacent Lands and Waters <br />Land owners adjacent to the facility arc the Bureau of Land Management (BLM), Nature <br />Conservancy, and Umetco Minerals Corporation. Land use adjacent to the Uravan site include <br />livestock grazing, uranium vanadium mining, and recreational use such as hunting and camping. <br />There are no permanent residences within a 5-mile radius of the site. Much of the surrounding <br />land is held by the BLM and is leased to ranchers for grazing. The United States Department of <br />Energy holds title to Upper Burbank Repository where the Naturita Mill Tailings reside. There are <br />no irrigated farmlands or domestic water wells within 5 miles of the disposal site due to the lack <br />of an adequate water supply and general inaccessibility of the area. Population in the area is low <br />with the majority of the population located near small towns. The closest towns are Naturita and <br />Nucla, approximately 12 miles southeast of the disposal area. Major land use activities in the <br />general area include agriculture in the Nucla area attd cattle grazing on the mesa tops and in the <br />river valleys. <br />5.0 GrROUNDWATER CHARACTERISTICS <br />5.1 HXdroloaic Setting <br />The Uravan area is situated between the Uncompahgre Plateau and the Paradox Basin and is <br />within the San Miguel RiverSasin. Regionally, hydrogeologic units potentially capable of <br />producing water in economic quantities include the Dakota and Burro Canyon Formations, the <br />Salt Wash Member of the Morrison Formation, and the Ennada, Kayenta and Wingate <br />Sandstones. Strata which are not capable of transmitting significant amounts of water and <br />represent aquitards in the area include the Brushy Basin Member of the Morrison Formation, and <br />the Summerville and Chinle Formations. The site is divided into two areas for the purpose of <br />describing the hydrogeology: the San Miguc] River Valley Area and The Club Mesa Area. The <br />San Miguel River Valley Area is defined as the valley bottom from the Town Area downstream to <br />the Atkinson Creek Disposal Area. The Club Mesa Area is directly west and southwest of Uravan <br />and includes the upper portion of the mill (B-Plant), the former ore storage and barrel storage <br />area, the heap leach site, Club Mesa Tailings Piles, and the Club Mesa Spray Area. <br />5.2 Regional Hydrogeoloev <br />The groundwater hydrogeology of the Uravan area has been described in numerous studies as <br />summarized in Appendix A of the Fina! Plans and Specifrcations jor Remedial Activities the B- <br />P1antRepository (LTmetco August,1998, Peel, 1994a and b). <br />Five principal hydrostratigraphic units occur within the upper 800 feet of sedimentary rocks in <br />Umetca-Uravan DA Februarylt,2000 13 <br />£t/8i 39t1d t1~~IlN dJOU J3110U L8LL7980L6 9Z:ti L00Z/St/90 <br />