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potential air blast, after each blast event. The peak velocity value and other instrumentation <br />data will be printed out as shown in Attachment 2.05.3(6)(a) -4. The recorded digital seismic <br />data will be downloaded and kept on file, along with the blast report from the contractor, at the <br />mine office. <br />Production <br />Bagged or dry ANFO explosive will be used at different times to properly fracture the <br />overburden at the NHN Mine. Powder factors will vary with each shot due to ever changing <br />geologic rock formations. Powder factors for each shot will be selected after the following <br />criteria have been taken into consideration: <br />a. Examining the highwall for geologic rock formation thickness and rock type. <br />b. Consult with the blast -hole drill operator for hardness of the rock and thickness within <br />the proposed blast area. <br />c. Consult with the overburden shovel operator for size of blasted rock and ease of <br />digging. <br />d. Location of shot in relationship to dwellings and other structures. <br />e. Reviewing previous seismic blast records for peak particle velocity. Peak particle <br />velocities for each shot will be closely monitored by seismic recorders and will be kept <br />below the 1 in /sec limit at any inhabited structure off the mine property. WFC will <br />make every attempt to keep the PPV as low as practical while still getting the <br />overburden fractured to our satisfaction. <br />Production patterns will vary in burden and spacing dimensions. Burden spacing will range from <br />10 to 15 plus feet. Spacing will vary from 15 to 20 plus feet. Burden and spacing dimensions <br />are governed on drill bit size (5.25 to 7 inch diameter), hardness of rock and degree of <br />fragmentation desired. Normal production blasting will be a rectangular pattern with on- echelon <br />delays. Staggered patterns have been used in the past with success and will be used in the <br />future as conditions warrant. Stemming will be washed gravel to contain the pressures. <br />Section 2.05.3 (6) (a) Page 4 <br />