2021-03-06_PERMIT FILE - C1981008A

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In conclusion, the shallow aquifer chemistry at the New Horizon Mine is unsuitable for domestic and irrigation purposes. Only the New Horizon 1 overburden, the underburden aquifer at both mining areas and the spoils and alluvial aquifers appear to be chemically suitable for use as livestock water. Aquifer yields are too low for irrigation use and can only be considered marginal to poor for domestic or livestock uses. Considering the combined criteria, only certain aquifers (underburden, spoils and alluvium) would be marginally suitable for use as livestock drinking water. Regional Surface Water Characteristics The New Horizon 1 and New Horizon 2 mining areas are drained by Tuttle and Calamity Draws, respectively. Both draws are perennial tributaries of the San Miguel River which in turn flows into the Dolores River and finally to the Colorado River. These river systems are explained thoroughly in Iorns' et al. (1965) USGS Professional Paper, Water Resources of the Upper Colorado River Basin - Technical Report. In this report, these river drainages are placed in the Grand Division of the Upper Colorado River Basin and in the subdivision between the Gunnison and Green Rivers. Because of the gradual increase in the development of water resources within the Grand Division in this century, streamflow records used for this report (1914-1957) were adjusted to reflect the level of water -use developments (diversions, dams, irrigation, etc.) that existed in 1957. Although the 1957 levels of development varied from basin to basin, the adjustments made in the reported streamflow records were useful for comparing stream characteristics among the different basins while accounting for the changes in streamflow and water quality caused by the increased developments. Since little additional activity (diversions, dams, etc.) has occurred within the San Miguel River basin since 1957, the information presented in Iorns' et al. (1965) report is considered to be representative of present conditions. Reeional Surface Water Flow The precipitation that falls on the basins within the Upper Grand Division of the Colorado is generated from large air masses originating from the Pacific Ocean and the Gulf of Mexico. These air masses originating from these sources are pushed high into the atmosphere, losing much of their moisture prior to entering these basins. The Pacific air masses dominate from October through April, and the Gulf of Mexico air masses dominate during late spring and summer. The higher streamflows within the Grand Division largely result from snowmelt during late spring and early summer. By late July, most stream discharges recede to base flow. Little contributions are made to stream discharges resulting from the infrequent summer thunderstorms. In the lower altitudes of the subdivision between the Gunnison and Green River, little snow accumulates during the winter months; therefore, most spring runoff events occur principally in the head waters of the Dolores, San Miguel Rivers, and in the LaSal Mountains. On a more local basis, short duration, high intensity thunderstorms that fall on undeveloped (natural) watersheds provide some of the summer runoff. In addition, return water from irrigation, and water from localized ground -water reservoirs augment streamflow during the summer months. Spring runoff is the principal contributor to flow during April, May and June with individual events during the summer months adding to the overall flow. Ground water also contributes to the stream baseflow during the summer months. Histograms of total monthly flows taken at the USGS gaging stations during the 1977 water year for the San Miguel River at Naturita, Colorado and the San Miguel River at Uravan, Colorado, respectively reflect the Page 2.04.7-15 March 2017 (TR -77)