Laserfiche WebLink
STATE OF COLORADO <br /> DIVISION OF MINERALS AND GEOLOGY <br /> Department of Natural Resources T,Q�(C ( VI / <br /> 1313 Sk erman St.,Room 215 �� L-I j j /1�� j�15 C O L O RA D O <br /> Denver,Colorado 80203 •� D I V I S I O N O F <br /> Phone:(303)866-3567 MINERALS <br /> FAX:(303)832-8106 G E O L O G Y <br /> REC LAMATION•MINING <br /> SAFETY•SCIE N CE <br /> Bill Owens <br /> DATE: June 3,2004 Governor <br /> Russell George <br /> TO: Tom Schreiner Executive Director <br /> Ronald W.Cattany <br /> Division Director <br /> FROM: Allen Sorenson/j�� Natural Resource Trustee <br /> RE. Review of Slope Stability Analyses, Hilltop Aquatic Investments,�LLC, ��// <br /> Raindance Sand and Gravel Mine,File No.M-2004-022 C& :Alkl� <br /> The Division of Minerals and Geology(DMG)geotechnical engineering staff has completed a review of <br /> i <br /> the slope stability analyses prepared by the Applicant's consultants for the above referenced proposed <br /> operation. DMG has determined that the proposed mining operation will have no adverse impacts on <br /> nearby structures worthy of protection; these structures are: <br /> • Town of Windsor water pipeline; <br /> • Poudre River Trail; <br /> • Eaton Ditch; <br /> • Everitt Barn. <br /> This determination relies on the mine operator's strict adherence to the setbacks from these structures that <br /> were input to the stability analyses. The Applicant must understand that these setbacks are enforceable <br /> conditions of the mined land reclamation permit,and that failure to abide by the setbacks will be looked <br /> upon as a serious violation of the terms of the permit. <br /> It should be noted that DMG identified one concern with the inputs to the Applicant's analyses,but found <br /> that this concern was not relevant to the determination of stability due to the magnitude of the mining <br /> setbacks in this particular case. The concern is with the shear strength values assigned to the weathered <br /> bedrock that underlies the sand and gravel deposit. This weathered material behaves as an over <br /> consolidated, stiff fissured clay, and upon unloading caused by mining this clay may degrade to its fully <br /> softened strength and locally to its residual strength,which can be quite low. However,in this case,with <br /> the required and enforceable setbacks,degradation of the weathered bedrock would not result in slope <br /> failure that could impact the nearby structures. <br /> cc: Carl Mount,DMG (via email) <br /> c:\acs\WANER MACHINE1My Documents\raindance stability analysis.doc <br /> Office of Office of Colorado <br /> Mined Land Reclamation Active and Inactive Mines Geological Survey <br />