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<br />. <br /> <br />or "recoverable reserve" is best defined as that portion of the entire <br />coal resource which can be recovered (extracted) through established <br />mining practices. <br /> <br />N <br />i- <br />en <br />U\ <br /> <br />That part which constitutes "measured'1 resources is only a portion <br />of an entire coal bed. Estimates are based oa mapping of individual coal <br />units. Points of observation in natural exposure along outc['ops~ mine <br />facies, core samples, and drill holes are used as a basis for the esti- <br />mates of remaining tonnage. Additional tonnage that may be present is <br />classed as l1indicated" or "inferred. II "Indicated" resources are identi- <br />fied by similar mapping and drill sample techniques, while "inferred" <br />L~E0~=~~~ ~~~ t~~~~ ~~ ~~o~c~ ~0~1 ~ed (ontinuity. Thickness and <br />continuity can be estimated fairly accurately givea current levels of <br />sophistication in assessing mineral resources (Averitt, 1975). <br /> <br />. <br /> <br />"Original" resources rerer to those pJ:'2sent prior to any mining taking <br />place, while lIremainingll resources are the unmined resources left in the <br />ground. "Recoverable" resources are those parts of remaining resources <br />which can be processed through ingenuity and increasingly sophisticated <br />techp.ology. Average recoverability is generally considered to be about <br />50 perc~nt, based on past mining experiences. Some strip mining results <br />in far better percentages of recoverability. Figure B.2 illustrates the <br />classification of total mineral resources, as adopted by the U.S. Geological <br />Survey and the U.S. Bureau of Mines. <br /> <br />The following analysis of Upper Colorado River Basin coal deposits <br />gives an overvie~ of the coal resources included in that area of each of <br />the five states in the Upper Colorado River Region. <br /> <br />Ar izona <br /> <br />Of the five Upper Colorado River Region states, Arizoaa is the only <br />one which has no coal deposits ~ithin the drainage area. The principal <br />coal-bearing region in Arizona is the Black Mesa Field. The northern <br />edge of this approximately 3,200 square mile field forms the southern <br />boundary of the Upper Colorado River drainage. The field and the Upper <br />Cretaceous coals within it are under the jurisdiction of the ~avajo and <br />Hopi Indians (Keystone, 1977). <br /> <br />. <br /> <br />The Black Mesa area, though outside the boundary of the study area, <br />should be mentioned because of its proximity and because of the mining <br />and transportation activities taking place there. Peabody Coal, which <br />currently holds the only lease in the field, is supplying coal to the Navajo <br />power plant on the Colorado River near Page, Arizona. A slurry pipeline <br />is carrying additional Black Mesa coal to the Mojave power plant in <br />southern Nevada. Water for all these operations is coming from deep <br />aquifers and does not use surface waters from the Colorado drainage at <br />this time (Peabody Coal Co., 1970).. <br /> <br />B-5 <br />