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1.0 Introduction <br />This report presents the results of a geotechnical investigation performed in connection <br />with planned improvements to the Chief Portal (the portal) located on Little Deadwood Gulch at <br />the May Day Idaho Mine Complex, on County Road 124, Hesperus, La Plata County, Colorado <br />(Figure 1). This investigation was performed to provide criteria for design of planned <br />improvements, and in fulfillment of requirements for additional geotechnical investigation <br />activities as described in the Colorado Division of Reclamation, Mining, and Safety's sixth <br />adequacy letter dated September 30, 2011, and the Permit 112d -1 Permit approval, dated <br />December 12, 2011. The scope of work included reviewing existing information, performing a <br />subsurface investigation, field and laboratory testing, engineering analyses to develop criteria for <br />design of the portal improvements, and preparation of this report. <br />1.1 Site Description <br />Historical mining activities (pre -1926) included construction of the portal, and disposing <br />of run -of mine -rock in the adjacent Little Deadwood Gulch (the drainage channel), a tributary to <br />the La Plata River. The portal was reconstructed in 2009 and the bench leading to the portal was <br />graded to remove debris at the portal entrance. <br />1.2. Objectives of the Work <br />The objectives of the planned improvements to the portal are listed below. <br />1. Remove pre -1985 fill from and re- establish the pre -mine drainage channel in Little <br />Deadwood Gulch; <br />2. Re- establish, and stabilize the portal as a escape manway and for mine ventilation; <br />3. Stabilize the section of Incas Road above the portal; and <br />4. Maintain all- terrain vehicle access to portal. <br />2.0 Investigation <br />The investigation included a document review, subsurface investigation, and geotechnical <br />analysis. Existing maps and publications of the geology of the portal vicinity were reviewed and <br />potential geological hazards discussed with Dr. David Gonzales of Fort Lewis College <br />(Gonzales, 2012). <br />The subsurface investigation included excavating five test pits at the approximate <br />locations shown in Figure 2. Test pits were excavated with a backhoe and extended to practical <br />Rule 6.5 Geotechnical Stability Technical Revision <br />Chief Portal <br />March 16, 2013 <br />Page 1 <br />