Laserfiche WebLink
The distance between Blast #105-02 and the rockfall azea is estimated at 4175 feet, based upon the <br />information provided by Mr. Smith on 6/4/02, and my estimate of the location of the rockfall azea. <br />The log for Blast #105-02 indicates that LCC determined that the maximum allowable weight of <br />explosives that the State's regulations allowed LCC to detonate within any 8-ms interval during this <br />blast was 8836 lbs/8 ms. The log indicates that LCC obtained this value by dividing the 5200-foot <br />distance value by the scaled-distance factor from Rule 4.08.4(10) of 55, rounding this value down to <br />94, and squaring this result. <br />LCC's use of the scaled-distance factor of 55 appears to have been incorrect, however, as that value <br />is used for distances between blasts and protected structures that range from 301 feet to 5000 feet, <br />and as LCC had estimated the distance between Blast #105-02 and the school as 5200 feet. <br />Using my estimated value of 3350 feet, and dividing that value by the scaled-distance factor of 55 <br />as prescribed by Rule 4.08.4(10), not rounding the result, and then squaring the result, I calculated <br />that the maximum weight of explosives per 8-ms interval allowed for Blast #105-02 by the State's <br />regulations would have been 37101bs/8 ms. This value is lower than LCC's calculated value. <br />The log for Blast #105-02 indicates that 7462 lbs of explosives were used to fill the holes drilled for <br />the blast, that the blast had 272 holes, and that the average weight of explosives per hole was 27 <br />lbs/hole (7462 lbs/272 holes). A review of the blast sketch indicates that these values appeaz <br />correct. <br />The maximum number of holes detonated within any 8-ms interval during Blast #105-02 is <br />recorded on the blast log as 5. The value for the maximum weight of explosives detonated within <br />any 8-ms interval during the blast is recorded as 135 lbs/8 ms, which the log indicates LCC derived <br />by multiplying their value of the average weight of explosives per hole of 27 ]bs/hole by LCC's <br />value of 5 holes detonated per 8-ms interval during Blast #105-02. <br />By reconstructing Blast #105-02 from its blast sketch, I determined that the maximum number of <br />holes that detonated within any 8-ms interval was 5. Multiplying the value of 271bs/hole that I had <br />verified above as being correct by 5, I concurred with LCC's calculation that the maximum weight <br />of explosives detonated within any 8-ms interval during Blast #105-02 was 135 lbs/8 ms. <br />LCC's value of 135 lbs/8 ms for the maximum amount of explosives detonated within any 8-ms <br />interval during Blast #105-02 is less than the State limit of 37101bs/8 ms that I determined to be <br />applicable to that blast. <br />Rule 4.08.4(10) indicates that for distances from 301 feet to 5000 feet between blasts and the types <br />of structures described in the rule, the maximum allowable ground vibration at the neazest protected <br />structure, measured as peak particle velocity (PPV), is 1.0 inches per second (ips). The rule <br />additionally indicates that for distances between blasts and protected structures of 5001 feet and <br />greater, the PPV limit is 0.75 ips. <br />The log for Blast #105-02 indicates the distance between the Primero School and the blast was 5200 <br />feet. This would indicate that the maximum ground vibration allowable by Rule 4.08.4(10) would <br />