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<br /> <br />Slopes below the Mahogany Ledge closely resemble those above the Ledge. They <br />are rocky and steep with essentially no A horizon. Large areas of the slope <br />below the Mahogany Ledge are covered with fresh oil shale talus. <br />Hung (1975) has estimated evapotranspiration and snow sublimation for the <br />OXY property leading to an estimate of average annual runoff. In summary, <br />his conclusions are: <br />1. Average annual precipitation on the plateau above the Mahogany Ledge <br />is about 15.8 inches of water. <br />2. Average annual evapotranspiration is expected to be about 20 inches, <br />plus or minus 10%. <br />3. Average annual sublimation is expected to be about 4.4 inches of water. <br /> 4. The predominantly loamy soil is expected to have a moisture-holding <br />• capacity of 1.7 - 2.3 inches of water per foot of soil. <br />5. The maximum accumulated amount of water at any one time (just as the <br />snow begins to melt) is expected to be 4.8 inches - within the moisture- <br />holding capacity of the soil. <br />6. Average annual runoff from the plateau is expected to be about 1 inch <br />of water. <br />7. Basin recharge by infiltration is expected to be minimal. <br />8. Existing groundwater supply probably represents an accumulation of small <br />precipitation excesses which have occasionally occurred over a very long <br />period. <br />Dry Gulch has not been observed to flow since OXY began work in June, <br />• 1972. Hung estimates flows from the plateau to be very low. During the <br />period of emplacement of the mineral waste disposal pile annual flow rates <br />will be zero or very low except during infrequent thunderstorms. Dry Gulch <br />-10- <br />