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Adequacy Items <br />SHB AGRA Project E92-7075 <br />_ ~~~ Page 7 <br />• ~~ Bi <br />e 6 -Please provide a map of known faulting and fracture patterns on the site. Was <br />e propagation of blast waves considered for along major faults or structural dislocations? <br />Possibility of reflection off faults? <br />Attachment 8 presents the mapped faults in the vicinity of the mine. Mapped faulting includes <br />two limited extent, northeast and northwest trending faults along the east side of the mine area <br />and a more extensive fault along the northeast side bounding Rabbit Mountain. The two limited <br />extent faults aze based on field mapping by Mallette (1962) where they are shown as inferred <br />features. Other investigators (Hunter, 1947 and Masters, 1957) do not indicate these features. <br />Accordingly, while the features aze shown, there is limited evidence for their existence. <br />Since any change in density of the subsurface materials can act as a reflection or refraction <br />surface, faulting would have the potential to affect propagation of blast-related seismic waves. <br />However, the faults do not bring rock of significantly higher density into contact with the <br />stratified limestone and shale sequence within the mine area. Accordingly, the potential for <br />refraction or reflection off a fault surface would not be expected to be greater than the same <br />propagation effects caused by bedding interfaces. <br />The analysis of existing data from the Lyons Quarry was evaluated by plotting data from blasts <br />recorded up dip, down dip and along strike from the blast location. As discussed in the blasting <br />• impacts report, there was no discernable difference in the magnitude of ground vibration as a <br />function of seismic wave propagation. Accordingly, the occurrence of faulting to the northeast <br />and east of the mine site would not be expected to have a detrimental impact on blast-induced <br />seismic wave propagation. <br />Will all Dowe Flats Quarry blasts be equal or less than Lyons Quarry Blasts (pounds of <br />exp o'sives, delays, etc.)? <br />Blasting procedures used at Dowe Flats will be identical to those currently used at the Lyons <br />Quarry. <br />What are the cumulative affects of both ground motion and air overpressure? <br />The cumulative effects of blasting over a long period of time have been investigated by Stagg, <br />et al. (1984). In this study, a test house was constructed in the path of a surface coal mine. The <br />response of the structure to over 580 blasts resulting in peak particle velocities from 0.10 to 6.94 <br />inches was monitored. The structure was then mechanically shaken at an equivalent 0.5 inches <br />per second for a total of 56,000 cycles before the first cracks appeared. This level of shaking <br />would be comparable to blasting five times daily for a period of 28 years. From the full scale <br />tests, the potential for cumulative effects of ground motions in the range of 0.5 to 0.8 inches per <br />second resulting from one to three blasts per week over the 25-year life of the Dowe Flats mine, <br />would be considered slight. <br /> <br />L~ A G R A <br />Earth & Environmen to/Group <br />