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iii iiiiiiiiiiiuiii <br />999 <br />STATE OF COLORP~UU <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Nannal Resources <br />1313 Sherman fit., Room 215 <br />Denver, Colorado 80201 <br />Vhone~13031866-35fi7 <br />FAY 1103) 811-8106 <br />Date: December 18, 1998 <br />To: Dan Mathews <br />From: David Berry <br />Re: TR 12 -Munger Canyon Miue - C-81-020 <br />I~ <br />~I~ .. <br />DEPARTMENT OI <br />NATURAL <br />RESOURCE. <br />Roy Romer <br />Go.-error <br />lames 5. LodrheaA <br />Esrcmice Duecror <br />nhchariB Long <br />Division Director <br />I have reviewed the hydrology aspects of the above-referenced technical revision submittal dated <br />October 12, 1998. The proposal to use the erosion control product is acceptable; however, <br />installation and long term field success should be monitored. Installation should be in accordance <br />with all manufacturers recomntendations. An alternate erosion control method such as riprap <br />might be required if ongoing erosion occurs afrer the proposal is implemented. We should <br />caution the operator that a noncompliance situation could develop if the product installation does <br />not successfidly correctthe erosion problems. Proper installation and subsequent maintenance <br />will be needed to ensure ongoing compliance. <br />I note that the submittal references our "insistence" that flow velocity calculations must assume <br />clear water runoff. Such an assumption may not be appropriate since storm runoff in most areas <br />of [lie state will carry significant sediment load. I suspect that the runoff which would occur at <br />the Munger Mine would contain sediment. Each site should be assessed with site specific <br />consideration, and we can probably allow a less conservative design assumption in this case. <br />Regardless, the proposed plans are acceptable as submitted, notwithstanding the need for correct <br />installation and maintenance to ensure ongoing compliance. <br />I have referred the bond estimate to Larry ~ utten for further review assignment. <br />Give,,call if you have any questions. <br />