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2. The revision included updated text that shows the proposed changes to the <br />SEDCAD curve numbers, including a bold notation of the "old" curve <br />number. There is, however, no supporting text or documentation explaining <br />why the curve numbers are being changed and why these changes are valid, <br />given the specific conditions at the Colowyo Mine. Please provide the <br />Division with an explanation and documentation as to why the SEDCAD <br />curve numbers are being changes from the single value to the proposed <br />range for each cover type listed on page 3 of the "Methodologies and <br />Assumptions" of Exhibit 7. Please include site-specific data for the <br />Colowyo Mine in this explanation. <br />3. On a somewhat unrelated note (unrelated to SEDCAD curve numbers), under <br />Section 1.9, Base Flow, in Exhibit 7, the current permit text reads "Base flows <br />were not used in any other pond design calculations [excepting West Pit and <br />Streeter]. Discharge of collected water from the open pits, as a result of <br />pumping, will not be permitted during a storm event equal to or greater than <br />the 10-year, 24-hour storm event." This text is not correct and should state <br />"less than or equal to the 10-year, 24-hour storm event." Please change the <br />permit text in Section 1.9 of Exhibit 7 to read "less than or equal to the <br />10-year, 24-hour storm event." <br />This concludes the preliminary adequacy review for Technical Revision 73. The <br />proposed decision date for this revision is 12 July 2008. Colowyo's prompt response to <br />this adequacy letter will ensure meeting this decision date. If you have any questions or <br />comments regarding this adequacy letter please call me at (303) 866-4929. <br />Sincerely, <br />James R. Stark <br />Environmental Protection Specialist <br />cc: Sandy Brown