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Response to Preliminary County Comments Received on March 17, 2011 <br />Idaho mill building) on the Idaho Mill property or moved off site for analysis. Core holes <br />will be abandoned in accordance with State of Engineer's office requirements and <br />reclaimed in accordance with DRMS reclamation requirements. In addition, pre-existing <br />access roads used for exploration drilling activities will be graded to conform to the existing <br />topography and reseeded using approved seed mixes. <br />Adequacy Issue #21 <br />Section 6.4.4(1) of Exhibit D indicates explosives will be utilized and directs the reader to <br />Exhibit 6.5, Geotechnical Stability Exhibit, for a blasting report. Attachment 6.5.6 contains a <br />certified report from Terry Morris, PE, addressing underground blasting at 1,500 foot depth. <br />Attachment 6.5.7 contains a statement from Franklin Drilling and Blasting, Inc., addressing <br />underground blasting at 1,000 foot depth. Neither of the statements addresses the potential <br />effects of blasting at or nearby surface. Near surface blasting has occurred at the site as recently <br />as September 3, 2009, during the construction of the illegal portal at the May Day 1 level. <br />Additionally, near surface blasting could be necessary during the re-construction of the failed <br />portal at the May Day 1 level and during construction of the access roads to the eleven drill pads. <br />Please provide the information required under Rules 6.4.4(1) and 6.5(4) for surface, as well as <br />underground, use of explosives. <br />Response #21 <br />Predicting surface air and ground blasting vibration is based on research information <br />published on March 8,1993 by the US Office of Surface Mining (OSM). OSM developed <br />the "scaled distance factor (SDF)" which is a conservative and accepted approach to <br />estimating ground vibration without the use of seismographs. For example, if a structure is <br />located from 0 to 300 feet from a blast site, the "scaled distance factor" would be 50. If the <br />blast site is located from 301 to 5,000 feet away, the SDF would be 55 and for blasts where <br />the structure is greater than 5001 feet away they would have a SDF of 65. Using the OSM <br />SDF, blasting can be used to predict potential impacts according to the following formula. <br />W= (D/SDF)' <br />Where <br />W=weight in pounds of detonated explosive in any period greater than 8 <br />milliseconds. <br />D=is distance in feet from the structure of concern <br />SDF=Scaled Distance Factor <br />As an example, <br />Revised <br />4/14/2011 <br />13