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<br />Proposed underground mining activity is not expected to contribute an increase in ground motion <br />over what is already expected with current surface mining activities. The charge weights per <br />delay period in surface blasting are of a larger size than typical underground blasting. The <br />energy released in surface blasting creates surface waves that radiate concentrically from the <br />energy source. Underground blasting typically results in lower surface wave amplitudes as the <br />path from the energy source along surfaces is much longer. The energy released in an <br />underground blast attenuates significantly before the wave train arrives at the surface. The <br />concern in underground blasting is usually limited to the effects on ground stability in the <br />immediate vicinity of the energy release, e.g. the effect on stope pillars. <br /> <br />MMC recommends confirmation of the relatively low vibrations created in underground blasting <br />by measurement with calibrated seismographs once the underground blasting commences. If <br />underground blasting is forecast to approach adjacent underground workings it would be prudent <br />to measure the ground motion at these adjacent locations. <br /> <br />Blasting creates a range of seismic affects, the most important of which are surface waves and <br />how they impact other surface facilities. Underground blasting creates very modest amounts of <br />surface waves especially when compared to open pit production blasting. <br /> <br />MMC will be pleased to verify these statements once underground blasting commences. <br /> <br /> <br /> <br />Sincerely, <br /> Colin M. Matheson, <br />President, Matheson Mining Consultants, Inc.