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Geotechnical Stability Exhibit <br /> • La Plata River Bridge (TR-3) La Plata River Bridge is currently designed <br /> to support an AASHTO truck loading of 54,000 pounds (Exhibit D-3 (TR-3). (Wilson, <br /> 2012) Construction activities were limited to reinforcing the bridge deck with steel I- <br /> beams and installing pedestal supports. The TR-3 is approved-construction pending <br /> • May No. 2 Operational Area Reclaimed Drainage Channel: (TR-4) is approved- <br /> construction is pending <br /> • Chief Operational Area(Portal)and Reclaimed Drainage Channel (TR-5) has been <br /> approved-construction is Rending. The Chief Portal was built before 1926. The portal <br /> was stabilized in 2009 and the bench leading to the portal was graded to remove debris at <br /> the portal entrance. <br /> Adjacent Land Owners <br /> On the basis of our observations and engineering analyses,we conclude that there are no areas <br /> adjacent to the permit area where potential off-site stability impacts could occur. There are no <br /> geologic structures or earthen facilities that have the potential to impact offsite locations. The <br /> closest adjacent properties considered in the assessment include the area parallel to the access <br /> road which was evaluated in connection with the new access road. The private owner property <br /> boundary is approximately 80 feet from the New Access Road cut slope and if the road cut failed <br /> (which is highly unlikely)where a final 3:1 slope was created,the land slide head cut would be <br /> approximately 40 to 45 feet from the private landowner's property boundary. See TR-2 <br /> submitted technical report and analytical data. <br /> Blasting Effects <br /> The effects of blasting on adjacent structures have been conducted by Mr. Terry Morris <br /> (Colorado Registered Professional Engineer No. 28457)and are presented in Attachment 6.5-1. <br /> Mr. Morris concludes that no structural damage is expected using up to 100 pounds of explosive <br /> per blast within the Mayday No. 2 underground workings. As the proposed blasting will be <br /> undertaken in the Mayday No. 1 underground workings further to the east, the existing blasting <br /> analysis is sufficient. As recommended, Wildcat will perform vibration monitoring if the size of <br /> the blasts exceed 200 pounds of explosive per delay. Wildcat Mining Corporation or a licensed <br /> contractor will be utilized to conduct site blasting activities. <br /> Predicting surface air and ground blasting vibration is based on research information published <br /> on March 8, 1993 by US Office of Surface Mining (OSM). OSM developed the "scaled <br /> distance factor(SDF)" which is a conservative and accepted approach to estimating ground <br /> vibration without the use of seismographs. For example, if a structure is located from 0 to 300 <br /> feet from a blast site,the"scaled distance factor"would be 50. If the blast site is located from <br /> 301 to 5,000 feet away,the SDF would be 55 and for blasts where the structure is greater than <br /> 5001 feet away would have a SDF of 65. Using the OSM SDF, blasting can be used to predict <br /> potential impacts according to the following formula: <br /> Wildcat Mining Corporation <br /> 112(d)Permit—May Day and Idaho Mine Application <br /> Revised November 14,2014 <br /> Rule 6.5 Page 3 of 7 <br />