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terrestrial sediments of the Tertiary , and marine deposits of the <br /> Pierre Shale. Channel shape and structure of the Purgatoire also vary <br /> within each of these formations as does the water quality. A natural <br /> deterioration of water quality can be expected as the stream flows out <br /> of the igneous terrains , through sodic sediments , and into marine <br /> sediments . Alluvial deposits in the area of the mines range from their <br /> current location to older terraces of forty to fifty feet above the <br /> Purgatoire. Buried channels filled with alluvium incised into the <br /> underlying Raton Formation have also been found . These alluvial <br /> deposits support typical hydrophytic vegetation characteristic of <br /> floodplains and contain ground water hydrologically connected to the <br /> Purgatoire River. <br /> 3. 1 Surface Water <br /> Surface water availability is directly related to <br /> precipitation received in the drainage . The climate summary, as <br /> described in the mine permit application, indicates total calculated <br /> precipitation for the mines should be 16.92 inches. Precipitation is <br /> measured at both the New Elk and Golden Eagle Mines by continuous <br /> recorders . Results for 1988 are contained in Table 3 of Appendix 1 . <br /> Measured precipitation at New Elk was 12. 25 while the Golden Eagle was <br /> 11 . 90 . These measurements are well below the calculated annual <br /> average . Indications of snow-pack and observed summer thunder showers <br /> were below normal, however, some recorder error may also enter into <br /> this below normal measurement. <br /> The Purgatoire River valley ranges in width from a few <br /> hundred to a few thousand feet. Use of the river in the area of the <br /> mines is limited to stock watering, flood irrigation on bottomland <br /> terraces, water supply for the New Elk Mine and preparation plant, and <br /> industrial supply for mining at both mines. Appendix 2 presents water <br /> uses for mine operations during 1988 which were calculated at 25.8 <br /> ac-ft. It is also estimated that approximately 6000 ac-ft per year are <br /> diverted from the upper Purgatoire River Valley for irrigation use. <br /> -12- <br />