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Figure 2 shows that for extremely low levels of production, say 10,000 bbls. per day or less, the Dry Gulch pile would suffice for at least 15 years. At the higher levels of production being considered, the Dry Gulch rock disposal pile would be complete in somewhat more than one year. The rock disposal pile will have an average oil content of approximately 9 gpt. Parts of it will be essentially barren marlstone of such low kerogen content it is not "ore" for any oil shale development process now being con- sidered. The OXY modified in-situ process is expected to utilize rock with a kerogen content well below that used by any other process using a surface retort, yet 9 gpt is too low even for the OXY process. The pile, then, will contain an insignificant amount of oil and what it does contain is not re- coverable by any known process. Oil Shale Waste Disposal Pile Stability The stability of waste materials depends on a number of properties of the materials contained in the pile, the construction methods, and the boundary conditions imposed on the dump materials during storing and during the sub- Sequent dump life. An examination of the materials in oil shale waste piles, which are produced by blasting, indicates this artifically fragmented material is similar in character and behavior to the naturally produced rock fragments of the exist- ing talus slopes which grade up from the base of the hills. Hand level measurements of both dump and natural slopes indicate similar angles in the range from 36 to 38°. The angles, in this case, indicate the dump materials and talus slopes have similar physical properties. A visual comparison be- • tween natural and man-made slopes is shown in Figure 3A. The man-made slopes on the left show almost identical slope angle and physical features as the three natural talus slopes on the right. Surveyed profiles of a talus slope -3-