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~ S ~ Southwestern Portland Cement <br />i~i <br />Blasting Related Ground Vibration <br />SI-IB AGRA Project E93-7038 <br />Page 2 <br />surface coal mines. As discussed in the Blast Vibration Analysis Report, these criteria are <br />considered to be applicable to the Dowe Flats Quarry and surrounding development. Because <br />the OSMRE regulations consider the effects of the frequency of ground vibration on building <br />response, the limiting peak ground vibration levels change with distance from the blast as does <br />the frequency content of the ground vibration. However, it should be noted that the OSMRE <br />regulatory limits are based on the peak ground velocity measured in any one of three <br />perpendicular directions. The analysis for the Dowe Flats project considered the resultant or <br />cumulative effect of the three components to result in a measure of vibration which is always <br />equal to or greater than any single component. Accordingly, comparison of the estimated of the <br />ground vibration values to the OSMRE standards provides a conservative assessment of <br />structural distress potential. <br />As a relative comparison, Table 2 summarizes the level of damage caused to residential <br />structures by various levels of ground vibration intensities. The ground vibration levels in Table <br />2 are the resultant peak particle velocity which as discussed previously are higher than the single <br />component value on which the OSMRE regulations are based. From a comparison of the ground <br />vibration data presented in Figures 3 through 8 and the damage levels summarized in Table 2, <br />blasting at Dowe Flats in the manner currently done at the Lyons Quarry will induce offsite <br />ground vibrations well below the threshold levels for damage to buildings. <br />An estimation of the relative levels of peak ground vibration currently experienced by the <br />various properties as a result of blasting at the Lyons Quarry was made as also noted on Figures <br />3 through 8. This estimation was made assuming the maximum charge weight per delay of 1600 <br />pounds and a typical charge weight per delay of 400 pounds. The distance was measured from <br />the existing "C" pit at the Lyons Quarry to the property. <br />In summary, this analysis shows that blasting at Dowe Flats, in the manner currently conducted <br />at the Lyons Quarry, will result in peak ground vibrations well below levels that are considered <br />damaging to one and two story residential buildings of modern construction. Sites to the south <br />of the Dowe Flats Quarry could experience peak ground vibrations exceeding the levels caused <br />by current blasting at the Lyons Quarry for the initial four to seven years, depending upon <br />location. After this time, mining will progress to the north a sufficient distance to reduce <br />vibrations levels at these locations to less than present. At the northern end of the Dowe Flats <br />property, maximum ground vibrations are estimated to exceed the current conditions over the <br />entire life of the quarrying operation due to the closer proximity to mining. Maximum levels are <br />however predicted to be well below levels that can cause damage in residences of modem <br />construction. Full-time monitoring is planned for all blasting as is currently done at the Lyons <br />Quarry and will enable verification of the predicted ground vibration levels. <br />L, A G R A <br />Eerth & Environmental Group <br />