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- 18 - <br />located along the boundaries of the Uncompahgre Plateau and in the <br />Rocky Mountain area to the east. The largest of these earthquakes <br />produced modified Mercalli intensities of VII. For the purpose of our <br />evaluation of the short term earthquake exposure at the site, we have <br />assumed that an intensity VII earthquake may occur along the south- <br />eastern boundary fault of the Uncompahgre Plateau. We estimate that <br />an earthquake of this size would produce a site intensity of VI in the <br />vicinity of the JD-5 lease. In evaluating seismic effects on struc- <br />tures for the short term operational phase of the project, Uniform <br />Building Code Seismic Zone 1 criterion will be appropriate. Seismic <br />coefficients of 0.025 g are appropriate in evaluating short term <br />stability of stockpiles and embankments. <br />When considering the long term seismic exposure, it is our <br />opinion that the historic record is not sufficient in evaluating <br />earthquake potential. Considering the length of the faults which <br />bound the Uncompahgre Plateau and the lack of detailed information on <br />their recent geologic history, it is our opinion that these faults <br />should be assumed capable of producing moderate to large earthquakes <br />with relatively long recurrence intervals. If a moderate to large <br />earthquake were located on these faults, site intensities of VII to <br />VIII would likely be experienced in the vicinity of the JD-5 lease. <br />The proposed subsurface waste rock disposal site, in the mine, is <br />invulnerable even in the event of a large nearby earthquake. <br />