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• <br />DIVISION OF MINERALS AND GEOLOGY <br />Depurlmenl of NaWral Resuurcc~ <br />1713 Sherman St., Room 27 5 <br />Denvcr, Colorudu 80203 <br />Phone: 13071 866-35h7 <br />FA% I3fR1 832 8106 <br />April 16, 1996 <br />Michael Keegan <br />Kaiser Ventures Inc. <br />P.O. Box 37 <br />Desert Center, CA 92239 <br />RE: Adequacy Review, TR-29, Chimney Rock Mine, Permit No. C-81-023 <br />Dear Mr. Keegan: <br />II~ <br />DEPAIZi'MEfJT OF <br />NATLJRAI. <br />RESOURCES <br />Ror Rome: <br />Gavemm <br />1amr~ S Unhhcul <br />E~eculi.~c Durr wr <br />hLChacl 8. Lm~; <br />Dnnum Dire mr <br />The Division has completed the adequacy review for Technical Revision 29 (Revision to <br />Appendix 7, Sediment Control Design Criteria). The following items require further <br />information or modifications: <br />1. Rule 4.05.6(11)(f) requires the combined upstream and downstream slopes of the <br />settled embankment not be steeper than Sh:ly, with neither slope steeper than 2h:ly. <br />Currently, according to the as built drawings in the permit document, ponds 2, 4, & <br />5 do not meet this requirement. These may be approved if the Division is provided <br />appropriate analysis that the embankments are stable. <br />2. Rule 4.05.6(11)(h) requires the minimum topwidth of the embankment shall not <br />be less than the quotient of (H+35)/5 where H, in feet, is the height of the <br />embankment as measured from the upstream toe of the embankment. Currently, <br />pond 2 does not meet this requirement. <br />3. Map 8, Drainage Control, and Table 7-7-1 contain 3 different Ditch Sf. This can <br />be cofusing at times and perhaps it would be in order to renumber the ditch <br />segments at this time. <br />4. Ditch 41b (west extension) and the Previous Road Ditch could not be located on <br />Map 8, Drainage Control. - <br />5. The supplemental information for each of the ponds should be associated with or <br />on the back of the "as builts" for each pond. Additionally, the D10, D50, and Dmax <br />for the Emergency Spillway Riprap is not listed for ponds 3, 4, and 5 as it is for pond <br />2. <br />• iiii iiiiuiii <br />STATE OF COLORADO <br />