Laserfiche WebLink
By reconstructing Blast #108-02 from its blast sketch, I determined that the maximum number of <br />holes that detonated within any 8-ms interval was 4. Multiplying the value of 2261bs of <br />explosives hole (that I had verified above as being correct) by 4 holes detonated during any 8-ms <br />interval, I calculated that the maximum weight of explosives detonated within any 8-ms interval <br />during Blast #108-02 was 9041bs/8 ms. <br />My calculated value of the maximum amount of explosives detonated per 8-ms interval during Blast <br /># 106-02 of 9041bs/8 ms is greater that LCC's recorded value of 678 Ibs18 ms. Both values, <br />however, aze less that the State limit of 4711 lbs/8 ms that I determined to be applicable to Blast <br />#108-02. <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 1.00 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 #108-02 indicates the distance between the Primero School and the blast was 5700 <br />feet. This would indicate that the maximum ground vibration allowable by Rule 4.08.4(10) would <br />have been 0.75 ips. However, a review of the infarmation provided by Mr. Smith on 6/4(02 <br />indicates the distance between the school and the blast was 3775 feet. Using the smaller distance, <br />the maximum ground vibration allowable by Rule 4.08.4(10) at the Primero School for Blast #108- <br />02 would have been 1.00 ips. <br />According to the log for Blast #108-02, a seismograph was located 1000 feet north of the blast. A <br />check of the seismograph's distance from Blast #108-02, based upon the information provided by <br />Mr. Smith on 6/4/02, indicates the distance from the seismograph to the blast was approximately <br />1100 feet. The log indicates that the seismograph recorded a maximum ground vibration level of <br />0.055 ips. <br />According to information provided by Mr. Smith on 5/29/02, the seismograph had a low end <br />frequency of 2 Hz; as such, the maximum level of airblast allowed by Rule 4.08.4(6)(a) at the <br />Primero School would have been 133 dB. According to the log for Blast #108-02, the seismograph <br />used to monitor Blast #108-02 recorded a value of 119.1 dB. <br />Comparing the log from Blast #108-02 with the requirements of the Lorencito permit, I determined <br />the following: <br />• The blast log indicates that ammonium nitrate was the blasting agent used. The permit states <br />that ammonium nitrate will be used. <br />• The log indicates that 87 holes were drilled for the blast. The permit states that the maximum <br />number of holes per blast will be 72. <br />• The log indicates that the holes were 23 feet deep. The permit states that the holes will be 30 to <br />60 feet deep. <br />• The log indicates that the average weight of explosive used per hole was 2261bs. The permit <br />states that the maximum weight of explosives used per hole will be 7401bs. <br />