Laserfiche WebLink
indicates the distance between the blast and the Primero School was 4500 feet, when used in <br />conjunction with LCC Map 2.05.03-4 "Surface Blasting Area" (certifted 7/31/01). <br />The distance between Blast #107-02 and the rockfall azea is estimated at 5750 feet, based upon the <br />information provided by Mrs. Smith on 6!4/02, and my estimate of the location of the rockfall azea. <br />The log for Blast #107-02 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 10,6091bs/8 ms. The log indicates that LCC obtained this value by dividing the 5700-foot <br />distance value by the scaled-distance factor from Rule 4.08.4(10) of 55, rounding this value down to <br />103, 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 to 5000 feet, and <br />as LCC had estimated the distance between Blast #107-02 and the school as 5700 feet. <br />Using my estimated value of 4500 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 />the maximum weight of explosives per 8-ms interval allowed for Blast #107-02 by the State's <br />regulations would have been 66941bs/8 ms. This is lower than LCC's calculated value. <br />The log for Blast #107-02 indicates that 17,3661bs of explosives were used to fill the holes drilled <br />for the blast, that the blast had 74 holes, and that the average weight of explosives per hole was 234 <br />lbs/hole (17,366 Ibs/74 holes, apparently rounded down). A review of the blast sketch indicates that <br />these values appeaz correct (although 17,3661bs/74 holes calculates to an average of weight of <br />explosives per hole value of 234.681bs/hole, which could be rounded up to 2351bs/hole). <br />The maximum number of holes detonated within any 8-ms interval Blast #107-02 is recorded on the <br />blast log as 3. The value for the maximum weight of explosives detoanted within any 8-ms interval <br />during the blast is recorded as 702 lbs/8 ms, which the log indicates LCC derived by multiplying <br />their value of the average weight of explosives per hole of 2341bs/hole by LCC's value of 3 holes <br />detonated per 8-ms interval during Blast #107-02. <br />By reconstructing Blast #107-OS from its blast sketch, I determined that the maximum number of <br />hales that were detonated within any 8-ms interval was 3. Multiplying my calculated value of 235 <br />lbs of explosives hole by my value of 3 holes detonated during any 8-ms interval, I caiculated the <br />maximum weight of explosives detonated within any 8-ms interval during Blast #107-02 was 705 <br />lbs/8 ms. <br />My calculated value of the maximum amount of explosives detonated per 8-ms interval during Blast <br />#107-02 of 705 lbs/hole is 3 Ibs/hole greater than LCC's estimate of 7021bs/hole. Both values are <br />less than the State limit of 66941bs18 ms that I determined to be applicable to Blast #107-02. <br />Rule 4.08.4(10) indicates that for distances from 301 to 5000 feet between blasts and the types of <br />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 />