ATTACHMENT T-6
T-6.
Provide a blasting plan to include the following: Identify as Attachment T-6
General information on anticipated drill (hole) diameter(s), bench height (blast depth), highwall
alignment, and other blast parameters that will affect relief, confinement, explosive distribution and other
factors that influence blast vibrations,
Maximum allowable air blast and ground vibration limits, control of fly rock and dust.
A.
Address how the following factors will be considered when designing blasts:
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Weather effects such as wind speed and direction, temperature inversions and cloud
cover on air blast and dust.
Geologic & topographic conditions including rock lithology, rock strength, rock
hardness, bedding planes, dip, depth of rock units, hydrology (wet holes), joints,
fractures, mud seams, and voids.
Use of the scaled distance formula or other mechanism to control vibration.
For protected structures.
For other structures.
Preventing injury to persons.
Preventing damage to public and private property outside the permit area.
Preventing adverse impacts on an underground mine.
Preventing change in the course channel or availability of ground or surface
water outside the permit area and;
Reducing dust outside the permit area.
Blasting Plan
The operator will comply with all blasting requirements as found in the West Virginia Surface Mining
Regulations.
The operator shall comply with all applicable state and federal laws in the use of explosives. A blaster
certified by the Department of Environmental Protection shall be responsible for all blasting operations
including the transportation, storage, and use of explosives within the permit area in accordance with the
blasting plan.
A.
Maximum allowable airblast and ground vibration limits;
Airblast limits shall not exceed the maximum limits as contained in the regulations at the location of
any dwelling, public buildings, school, church, or community or institutional building outside the
permit area. The operator will conduct periodic monitoring to ensure compliance with the airblast
standards. The Director may require airblast measurements of any or all blasts and may specify the
locations at which such measurements are taken.
If necessary to prevent damage, the Director may specify lower maximum allowable air blasts for use
in the vicinity of a specific blasting operation. The air blast measuring systems used will have any
upper end flat-frequency response of at least 200 Hz. The peak particle velocity in any one of three
mutually perpendicular directions shall not exceed the following values at any protected structure.
Seismograph Measurement
1.25
1.00
0.55
Distance to the Nearest Structure
O to 300 feet
301 to 5,000 feet
5,001 feet or greater
T-6.
(Continued)
A.
General Blasting Plan
Patriot Mining Company, Inc. hereby agrees to be subjected to the terms of 22-3A-5-(g) of the West
Virginia Surface Mine Regulations. A blasting plan for the surface mine was developed based on the
continued mining at the adjacent surface mine permits. Currently, the rotary air drilling equipment
provides a drill hole with a diameter of approximately 6 ¼ inches. The diameter of the drill hole may
vary depending on the hardness of the strata encountered and geology of the overburden to be
fractured. The following criterion was considered when preparing the blast design.
1.
The maximum weight of explosives detonated at one time will not exceed the maximum
allowable weight as calculated using the scaled distance formula unless waivers allowing
alternate peak particle velocities, signed by the owners of the structures are first obtained. If
alternate PPV are proposed, seismic monitoring must be conducted at these structures.
2.
The burden in feet shall be 2-3 times the diameter of the borehole in inches. As a rule of
thumb, the borehole diameter should be approximately one-tenth (0.1) of the face height.
3.
The spacing shall be 1 to 2 times the burden.
4.
The hole depth shall be 1.5 to 4.0 times the burden
5.
The stemming will be 0.5 to 1.3 times the burden. Stemming will consist of drill cuttings or fine
gravel. In wet holes, only fine gravel will be used.
6.
The powder factor will range from 0.25 to 2.5 pounds of explosives per cubic yard of
overburden being shot with the most typical being 0.5 to 1.0 pounds per cubic yard.
Blasting Materials
The types of explosives to be used will consist of the following materials:
Primers will be selected from the list of dynamite, water gels and cast primers. Bulk and/or packaged
explosives will be of ANFO (Ammonium Nitrate and Fuel Oil), water gels and assorted slurries.
General nomenclature identification for these items are used as to selected brand names have been
selectively eliminated from the listing of materials.
Unavoidable Hazards
In the event of an emergency situation where rain, lightning, adverse atmospheric conditions,
personnel or public safety, would dictate an unscheduled detonation, it will be recorded on the
blasting log. The regulatory authority will be notified before or as soon as possible after the
unscheduled detonation.
Wet Holes
Ammonium nitrate and ANFO have no water resistance and contact with water should be avoided.
Gelled and cross linked slurries provide the best water resistance and should be used where ground
water is a problem. ANFO can be used but requires dewatering by pumping or by detonating a small
charge in the hole. A plastic sleeve can be inserted then filled with a dry material with a specific
gravity greater than 1.0 (heavier than water). ANFO can also be used in wet holes by packaging it in
water resistant cartridges or plastic bags. A water resistance primer such as a gelatin dynamite or
cap sensitive water gel or slurry should be used. When shooting wet holes, it is best to use gravel for
stemming and avoid drill cuttings.
T-6.
(Continued)
1.
Weather Effects
The effects of various types of weather can make it difficult to predict or control the motion of air
concussion waves. Heavy cloud or a temperature inversion (a layer of warm air above a layer of cold
air) can cause air blast to bounce back toward the ground. Wind can force air concussion in the
direction it is blowing. Wind direction is also important when mining near structures or dwellings as
they can blow dust onto these structures. The combined effect of wind and temperature inversion can
cause sever air blast problems.
2.
Geologic and Topographic Conditions
There are no inconsistent geologic formations within the boundaries of the proposed blasting. The
overburden at the blast site consists of sandstone and shale. Shale and most sandstone are generally
classified as softer rocks but may require more blasting energy than harder more brittle rock types.
Voids and zones of weakness such as fractures, faults and mud seams create serious blasting
problems. Explosive energy seeks the path of least resistance and result in poor fragmentation,
excessive flyrock and/or airbase. When loading holes in areas of inconsistent geologic formations,
inert stemming material should be loaded through these weak zones. Jointing and bedding planes can
affect both fragmentation and highwall stability. Close jointing usually gives good fragmentation
while wide jointing does not. The best solution to control these zones of weakness is smaller blast
holes tighter pattern or closer together.
The location of all known mine workings within and adjacent to the blasting area, along with strike
and dip of the coal seams and all mapped lineament traces have been shown on the Blasting Map to
aid the certified blaster in the blast design. The keys to characterizing the rock are a good geologist
and a good driller. Knowledge of rocks and their physical characteristics can help in the initial blast
design. An observant driller can help in assessing rock variations. Slow penetration, vibration and
excessive noise indicated hard rock while fast penetration and a quiet drill indicate softer rock. No
resistance, absence of drill cuttings or return of air indicates a void created by a underground mine
heading.
Any geologic anomalies including mine voids encountered by the drill operator while drilling will be
noted and conveyed either to the foreman or directly to the blaster prior to any shot being loaded.
Any written notes will be attached to the respective blast log.
3.
Scaled Distance Formula
A.
The nearest protected structure to the blast site will be used to determine the maximum
allowable weight of explosives to be detonated during any eight (8) millisecond delay.
B.
Other structures, such as roads, power lines, gas lines, etc. shall be used if they are closer than
the protected structure unless signed waivers allowing alternate peak particle velocities are
obtained from the owners of the structures. If alternate PPV’s are proposed, seismic
monitoring must be conducted at the nearest structure.
Seismograph monitoring may be required at more than a single site, if alternate PPV limits,
present an options to the blaster-in-charge to exceed the scaled distance formula while still
protecting the public and associated structures and remaining under the alternate PPV limit.
T-6.
(Continued)
4.
Preventing Injuries to Persons
Information prevented in this Section and T-8 shall minimize the risk of injury during the loading
and blasting operations.
Post Blast Safety
Following a blasting event, the blaster should stay in the shelter or other protected structure fro a
minute or two to allow flyrock to drop and any toxic gases to disperse. The leads shall be
disconnected or shunted and the firing switch locked. The blaster shall then inspect the site looking
for evidence of misfires, unexploded materials or burning of explosive materials. A check for loose
rock, back break, overhangs or other unstable conditions should also be conducted. Other personnel
shall be prohibited from entering area until it is certain that no hazards exist.
Misfires
When misfired holes or undetonated explosives remain after a blast is fired, a hazardous condition
exists until the materials are properly removed. In the event of a known or suspected misfire, a
waiting period of at least 30 minutes shall be observed. After the waiting period, the blaster shall
inspect the area and check all observable initiation system components using the appropriate
instrument checks.
Where possible, unfired charges shall be reconnected and fired successfully. If this procedure cannot
be conducted safely, then the maximum amount of charge shall be neutralized. Methods used to
neutralize the explosive column may include:
a.
washing out the explosive column with a stream of water and removing the cartridge with nonsparking, retrieving tools;
b.
placing another primer on top of the powder column and detonating it;
c.
drilling, loading and firing another hole adjacent to the misfire;
d.
digging the charge out.
The last two alternatives are extremely hazardous and should only be considered as a last resort.
Only competent experienced personnel should be involved in the disposal of misfires or the workings
of personnel and equipment in areas where misfires are present.
Should a shot misfire, and it will be determined by the blaster-in-charge that the stemming material
be washed out with air or water, a replacement primer and cap would be placed on top of the powder
column and choice stemming material replaced in the blast hole, the hole would then be fired. Based
upon the opinion of the blaster-in-charge, mats may be employed to further insure that flyrock is
contained and air-over-pressure controlled.
5.
Preventing Damage Outside the Permit Area
Properly designed blast in accordance with the criteria in Attachment T-2.B shall minimize the risk of
damage due to ground vibration, Airblast and/or flyrock. Compliance with the maximum weight of
explosives as calculated by the scaled distance formula shall prevent excessive ground vibrations.
Adequate stemming shall be used to minimize airblast and blasting shall be avoided during periods of
inclement weather. Flyrock shall be controlled by using the correct powder factor for the type or
rock that is being blasted, proper burden and proper stemming. Even with good blast design and
careful planning; flyrock may occur and must always be protected against. Flyrock, including any
blasted material traveling along the ground, shall not be cast more than half the distance to the
nearest dwelling and in no case beyond the limits of the permit area. Flyrock has not been a problem
in the adjacent mining operations. Mats shall be used should flyrock present a problem.
T-6.
(Continued)
6.
Preventing adverse impacts on an underground mine
There are no underground mines within 500 feet of the proposed blasting. Abandoned mine workings
in the Sewickley and Pittsburgh coal seams are located approximately 300 and 440 feet below the
proposed surface mining area. See Attachment T-2 labeled “Site Specific Blast Design”.
7.
Preventing change in surface / groundwater
No change in surface / groundwater is anticipated from the permit application. Surface and Water
monitoring locations are identified in Section U of the MR-4 application. The monitoring sites will be
monitored quarterly and if a problem arises the appropriate steps will be taken as outlined in Section
J of the MR-4 application.
8.
Dust Control
Water wagons shall be used to control dust on the haulroads and in the working areas. Dust from
blasting shall be controlled by proper blast designs. The use of adequate stemming and the correct
powder factor for the type of overburden being shot shall minimize the amount of dust from the blast,
while, insuring good breakage of the overburden. The velocity and direction of the wind are also
important factors in reducing dust outside of the permit area. Blasting should be avoided on windy
days, especially when it is blowing in the direction of dwellings or other structures.