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GENERAL41266
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GENERAL41266
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Last modified
8/24/2016 8:00:23 PM
Creation date
11/23/2007 11:06:52 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1996084
IBM Index Class Name
General Documents
Doc Date
6/17/2002
Doc Name
Investigative Report Citizens Request for Inspection
From
DMG
To
Lorencito Coal Company
Permit Index Doc Type
Citizen Complaints
Media Type
D
Archive
No
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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 #107-02 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 information provided by Mr. Smith on 614/02 <br />indicates the distance between the school and the blast was 4500 feet. Using the smaller distance, <br />the maximum ground vibration allowable by Rule 4.08.4(10) at the Primero School for Blast #107- <br />02 would have been 1.0 ips <br />According to the log for Blast #107-02, a seismograph was located 1100 feet north of the blast. A <br />check of the seismograph's distance from Blast #107-02, based upon the information provided by <br />Mr. Smith on 6!4102, indicates the distance from the seismograph to the blast was approximately <br />1350 feet. The log indicates that the seismograph recorded a maximum ground vibration level of <br />0.11 ips. <br />According to the information provided by Mr. Smith on 5/29/02, the seismograph microphone had a <br />low end frequency of 2 Hz; as such, the maximum level of airblast allowed by Rule 4.08.4(6)(a) at <br />the Primero School would have been 133 dB. According to the log for Blast #107-02, the <br />seismograph used to monitor Blast # 107-02 recorded a value of 129.7 d3. <br />As mentioned previously, Rule 4.08.5(17) requires seismograph and airblast records, where <br />required, to contain calibration signals of the seismograph's gain setting, or certifications of annual <br />seismograph calibrations. None of these appeazed available. <br />Comparing the log from Blast #107-02 with the requirements of the Lorencito pemut, 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 74 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 the holes were 21 feet deep. The permit states that the holes will be 30 to 60 <br />feet deep. <br />• The log indicates that the average weight of explosive used per hole was 2341bs. My review <br />estimated the average weight of explosive used per hole was 235 lbs. The permit states that the <br />maximum weight of explosives per hole will be 7401bs. <br />• The log indicates that the total weight of explosives used in the blast was 17,3661bs. The <br />permit states that the maximum weight of explosives used per blast will be 54,7201bs. <br />• The log indicates that explosive material was placed in the holes no closer than 8 feet from the <br />surface. The permit states that explosive material will be placed no closer that 10 feet from the <br />surface. <br />• The log indicates that the blast was initiated with an electric initiation system. The permit states <br />initiation will be with anon-electric system. <br />• The log and blast sketch indicate that surface delays along rows were 17 ms. The permit states <br />that surface delays along rows will be 9 ms. , <br />
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