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<br />The stratigraphy underlying the Piceance Site is the same as that described above for <br />the region. Specific geology for the pipeline corridor and the Parachute Site are not <br />included in this Exhibit because mining does not occur at either area. Amore detailed <br />geology discussion for the entire project area is provided in the BLM Draft EIS for the <br />Yankee Gulch Project. <br />D.7 Nahcolite Resource <br />The Piceance Creek Basin contains the world's largest and most economically <br />significant nahcolite resource. Conservative estimates of in-place nahcolite in the basin <br />have been reported at 29 billion tons (Dyni 1981). The nahcolitic oil shale has been <br />estimated to cover some 257 square miles of the Piceance Creek Basin (Smith et al. <br />1973). The thickest and richest nahcolite-bearing stratigraphic intervals are known to <br />occur in the depositional center of the basin in T1S and T2S, R97W and R98W. The <br />Yankee Gulch Joint Venture Leases, of which 4,084 acres are included in the Piceance <br />Site, encompasses approximately 4,954 acres overlying the depositional center of the <br />basli~. Current drill hole data taken from near monitoring well 20-1 and the <br />experimental test cavities indicate the presence of significant sodium resources, with a <br />total saline interval almost 770 feet thick at an average nahcolite content in excess of 26 <br />percent by weight (Dyni 1974). This equates to 333 million tons of nahcolite per square <br />mile. Considering other drill hole data at the Piceance Site, this results in an in-place <br />average nahcolite resource of 313 million tons per square mile for a total Piceance Site <br />resource estimate of some 2 billion tons of nahcolite. <br />Studies of nahcolite-rich intervals in the Saline Zone have shown that 26 mappable <br />horizons are present within an 800-foot interval from about 1,400 to 2,200 feet below <br />ground surface. Individual beds may be all nahcolite or nahcolitic/halite or grade into <br />halite. Beneath the Piceance Site, there are seven nahcolite beds greater than 6 feet thick <br />that have in excess of 43 percent nahcolite by weight. The Love Bed is a tan <br />microcrystalline nahcolite interval present at 1,700 feet below ground level at <br />monitoring well 20-1. The Love Bed is 7.4 feet thick here and averages 53 percent <br />nahcolite by weight. The Greeno Bed is a honeycomb disseminated nahcolite-rich bed <br />located at a depth of 2,062 feet below grade at monitoring well 20-1. At that location, <br />the Greeno Bed is 5.9 feet thick and averages 76.5 percent nahcolite by weight. The <br />laterally continuous TI Bed is a little deeper than the Greeno Bed, but neither of the <br />Piceance Site drill holes was drilled deep enough to intersect this unit. It is present <br />throughout the central Piceance Creek Basin and in nearby Horse Draw Mine, where it <br />is 6 feet thick and averages 65 to 70 percent nahcolite by weight. <br />D.S Overburden <br />The nahcolite resource is generally located between 1,400 and 2,200 feet below ground <br />surface, based on a surface elevation of approximately 6,200 feet. A 150-foot buffer will <br />D-16 <br />