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<br />• American Soda proposes to extract nahcolite by solution mining a vertical <br />stratigraphic sequence of the Saline Zone that contains both stratiform (bedded) and <br />disseminated nahcolite. <br />stratiform Nahcolite -The stratiform nahcolite is composed of discrete <br />nahcohlite beds that are commonly interstratified with thin beds and laminae of oil <br />shale. stratiform nahcolite is present in a white granular/crystalline form and a <br />more common brown to tan microcrystalline form that is dense and nonporous. <br />stratiform crystalline nahcolite occurs primarily in the upper and lower salts of the <br />Saline Zone where, in the same stratigraphic interval, it is laterally coincident with <br />halite and nahcolitic halite. This geochemical facies change where halite and <br />nahcolite coexist can occur over a relatively short horizontal distance, commonly <br />referred to as the transition zone (Daub et al. 1985). stratiform crystalline nahcolite <br />beds are present in the area of monitoring well 20-1, where they range from 1.2 to <br />12.6 feet thick and contain nahcolite in the range of approximately 44 to 87 percent <br />by weight. <br />Disseminated Nahcolite -Disseminated nahcolite is the most common type <br />and is composed of nahcolite bodies dispersed throughout an oil shale matrix. The <br />disseminated type makes up in excess of 85 percent of the total nahcolite resource in <br />the basin (Dyni 1981). The disseminated type comprises nahcolite aggregates and <br />crystals, often with high concentrations within a given oil shale interval such that <br />• the nahcolite-bearing stratigraphic interval has lateral continuity. Nahcolite <br />aggregates are bodies composed of two or more individual nahcolite crystals that <br />collectively make up a coherent, solid mass. Aggregate sizes range from less than 1 <br />centimeter to well over 1 meter in diameter. They are commonly dark reddish- <br />brown and are somewhat translucent. Individual nahcolite crystals are commonly <br />found scattered throughout the oil shale. The abundance of nahcolite crystals <br />disseminated in a given oil shale interval is highly variable, ranging from sparsely <br />disseminated (less than 20 percent nahcolite) to honeycomb in appearance (greater <br />than 60 percent nahcolite). <br />Studies of nahcolite-rich intervals in the Saline Zone have shown that 26 mappable <br />horizons are present. Individual beds may be all nahcolite or nahcolitic halite or <br />grade into halite. Beneath the Piceance Site, there are seven nahcolite beds greater <br />than 6 feet thick that have in excess of 43 percent nahcolite by weight. The Love Bed <br />is a tan microcrystalline nahcolite interval present at 1,700 feet below ground level <br />at monitoring well 20-1. The Love Bed is 7.4 feet thick here and averages 53 percent <br />nahcolite by weight. This horizon alone contains a total nahcolite resource of <br />approximately 57 million tons. The Greeno Bed is a honeycomb disseminated <br />nahcolite-rich bed located at a depth of 2,062 feet below grade at monitoring well 20- <br />1. At that location, the Greeno Bed is 5.9 feet thick and averages 76.5 percent <br />nahcolite by weight. The laterally continuous TI Bed is a little deeper than the <br />Greeno Bed, but neither of the Piceance Site drill holes was drilled deep enough to <br />• intersect this unit. It is present throughout the central Piceance Creek Basin and in <br />nearby Horse Draw Mine, where it is 6 feet thick and averages 65 to 70 percent <br />Amencan Soda, L.L.P. 7_11 <br />Commercial Mine Plan <br />August 18, 1998 <br />