2020-03-30_HYDROLOGY - M1981021 - Laserfiche WebLink

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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT on the northern slope of Disappointment Valley, the underground workings are approximately 600 ft below the ground surface (CDM & Denison, 2009). Vegetation is relatively sparse in the area and consists of various grasses as well as sagebrush and cactus on the valley floors. Pinon-juniper communities are present on the bounding slopes and ridges of small mountain ranges. The initial mining permit (May 1978) for the Sunday Mine estimated actual natural vegetation cover at the mine area of 16% and consisting of: 10% pinon- juniper, 14% small sagebrush, 43% grasses (galleta 26%, Indian ricegrass 17%, and blue grama 2%), 21% Russian thistle, with the remaining cover consisting of cactus, yucca, snakeweed and other miscellaneous forbs. The valley floor vegetative cover was estimated at 15% consisting of: 51% Russian thistle, 34% grasses (galleta 21%, blue grama 10%, Indian ricegrass 3%), 4% snakeweed, 11% big sagebrush, juniper, shadscale saltbrush, cactus, and miscellaneous forbs (DRMS, 1977). Climate summary data acquired from the Western Regional Climate Center (VVRCC) is shown in Table 2-1. (WRCC, 2020). The data are from the National Oceanic and Atmospheric Administration (NOAA) Co-op station No. 058560 located in Uravan, Colorado. The Uravan station is the closest recorded climatic data with the longest period of record (1960 to 2016). Based on a period of record from 1960 to 2016, average low and high air temperatures for Uravan are 37.3 and 69.1 °F, respectively. The average temperature is 53.3 °F. The average annual precipitation is 12.54 inches and average snowfall is 11.1 inches. Graph 2-1 shows a graphical representation of average monthly precipitation. The annual evaporation from a free- water surface was estimated to be 65 inches along the San Juan River and slightly less than 45 inches in the mountains (Farnsworth and others, 1982). 3.0 HISTORIC MINING Mining at the SMC has occurred since the 1950s. Historical records indicate at least nine companies have been involved in ownership or mining of the SMC claims since that time. Companies with ownership included Matterhorn Mining, Climax Uranium, Union Carbide Corporation, Atlas Minerals, Energy Fuels Nuclear, International Uranium Corp., Denison, and EFR. PRM acquired the mines in April 2014. Colorado required mining permits beginning in 1977, and formal records of mining and permitting activities at the SMC are available on the DRMS website. According to Denison (2008), historical maps show the SMC in operation in the 1950s. Adkins (2015) indicates that Western Water& Land, Inc. 4