2013-05-10_REVISION - M1977193 (3)

Home Browse Search

Azurite, Inc. 10001 CR 12 P.O. Box 338 Cotopaxi, Colorado 81223 719- 942 -4178 May 8, 2013 Tim Cazier, Environmental Protection Specialist Colorado Division of Reclamation, Mining, and Safety 1313 Sherman Street Room 215 Denver, CO 80203 RE: M- 1977 -193, Tezak Heavy Equipment Company, Inc., Highwall Stability Exhibit Tezak Heavy Equipment Company, Inc. owns and operates The T.H.E. Aggregate Source, LLC, granite gneiss mine located on the western edge of Canon City, Colorado. The deposit has been described as a massive bedrock outcrop of "migmatitic precambrian gneiss, chiefly feldspatic - biotite- quartz- plagioclase gneiss with minor amounts of hornblende gneiss, calc- silicate gneiss, and garnetiferous and sillimantic varieties." The granite gneiss has been extensively mined over the past 15 years, exposing a 350' high x 6001ong highwall excavated to 40'highwall benches ( @.25:1, H:V) with 20' bench widths. At final build -out of the granite gneiss deposit, the largest single run of excavated highwall structure may total 680'high and up to 3000'long. The proposed final highwall bench configuration specifies 40'high x 30'deep benches ( @.25:1, H:V). Field work performed in early 2013 confirmed the 1997 field data as noted in the original highwall investigation as well as documenting some change in certain aspects of the granite gneiss deposit. The purpose of this investigation was to confirm rock characteristics pertaining to mine plan considerations for maximum final highwall stability as well as confirmation of overall long -term slope stability. Rock Characteristics, Foliation, and Jointing The granite gneiss is a competent, massive sequence of granitic (feldspar, quartz, biotite) mineral composition with banded and layered metamorphic rocks interspersed with migmatitic zones of pink feldspar -rich igneous rock. Compositional banding is highly variable from a fraction of an inch to many feet across an outcrop face of like (similar) mineral. For the most part, field measurements of foliation strike and dip resulted in a strike of N30W and near vertical to 85 degree dip to the east, although a number of exceptions to this general trend were encountered in the central portions of the existing highwall exposure. The N30W trending foliation direction appeared variable at some measuring locations to strikes ranging from NIOW to N10E and portraying slightly lower dip angles (70 -85 degrees) along the northern portions of the existing highwall at mid - levels. Foliation direction appears to be fairly consistent in a N by W direction while displaying local variation up to 40 degrees across the length of the excavated highwall