Current through Register Vol. 48, No. 39, March 25, 2024
Subpart 1.
Air overpressure standards.
Air overpressure standards:
A. Air overpressure on lands not owned or
controlled by the permittee shall not exceed 130 decibels as measured on a
linear peak scale, sensitive to a frequency band ranging from six cycles per
second to 200 cycles per second.
B.
All open pit blasts shall be monitored by the operator. Monitoring stations
shall be located adjacent to the nearest structure located on lands not owned
or controlled by the permittee, and where the commissioner deems necessary to
investigate complaints. Scram operators are not required to conduct air
overpressure monitoring except as required for complaint
investigation.
C. All open pit
mining operators shall keep a blaster's log of production blasts for a period
of at least six years containing the following:
(1) date and time of blast;
(2) type of explosive used;
(3) ignition layout with locations of blast
holes and time intervals of delay;
(4) pounds of explosives per each delay of
eight milliseconds or more;
(5)
total pounds of explosives;
(6)
type of material blasted;
(7)
monitoring locations and results of monitoring when conducted;
(8) meteorological conditions, including
temperature inversions, wind speed, and directions as can be determined from
the U. S. Weather Bureau, and ground-based observations;
(9) directional orientation of free faces of
bench to be blasted; and
(10) other
information which the commissioner finds necessary to determine if the
standards of this part and part
6130.3800 are achieved.
D. If a focusing condition is
detected which could cause the blast to adversely affect populated areas,
blasting shall be postponed until the condition is no longer present.
E. Blasting shall take place only during
daylight hours unless a hazardous condition requires blasting at another
time.
Subp. 2.
Ground vibration control.
Ground vibration control:
A. The maximum peak particle velocity from
blasting shall not exceed one inch per second at the location of any structure
located on lands not owned or controlled by the permittee.
B. The permittee shall either:
(1) monitor production blasts for peak
particle velocity using a seismograph capable of measuring three mutually
perpendicular peak particle velocities, with the peak particle velocity being
the largest of these measurements; or
(2) utilize the scale distance formula
W=(d/60)2
where: W= the charge weight per delay (eight milliseconds or
more), and d= the distance (in feet) from the blast to the nearest structure
located on lands not owned or controlled by the permittee to determine the
weight of allowable explosive per decay.
When the monitoring is chosen, or complaints are received,
seismic measurements shall be conducted adjacent to the nearest structure
located on lands not owned or controlled by the permittee and where the
commissioner deems necessary to investigate complaints.
C. In the event of a complaint or
when ground vibrations have or are likely to exceed the one inch per second
standard, the commissioner shall require permittees using underground mining
methods to maintain a blaster's log for the purpose of assessing ground
vibration control.
Subp.
3.
Retention of monitoring data.
All monitoring data collected shall be saved for a period of
six years and made available to the commissioner upon request.
