Flyrock travels at 300 ft. per second at 204.5 mph, many injuries occur far from the blasting zone. Where blasting occurs in populated areas it is a hazard to people, structures, and equipment NOT on the blasting site. Anyone or any animal within 1500 ft. of a blasting site need to take cover. Flyrock can travel in any direction or multiple directions.
On June 11, 2007, in West Lebanon, NH, Green Mountain Explosives detonated a quarry blast that resulted in flyrock being thrown about 3,000 feet (10 football fields) into an industrial park doing damage to a building and vehicles. This same blast also sent flyrock about 4,000 feet that landed on Lebanon Airport property, including a runway. The manager of Technical Services of Green Mountain Explosives, Tim Rath, is representing Rivers as his blasting expert in environmental court. Mr. Rath testified at an Act 250 hearing on May 2, 2006, that during a blasting event the nearby residents near Rivers' quarry should be in their homes and not out on their property. When asked specifically about the danger from flyrock, Mr. Rath said, "You can never say never." No matter how careful a blaster is there is no certainty a blast will not cause flyrock. There are over 20 homes within 3,000 feet of the proposed quarry with the closest property lines just over 200 feet away.
In a government study released in 2001:
Seven fatalities due to flyrock and lack of blast area security were reported in surface coal mines and sixin nonmetal mines. Out of these, two fatalities (one each in coal and nonmetal mines) occurred outsidethe mine property.
IME has defined flyrock as the rock(s) propelled from the blast area by the force of an explosion [IME1997]. A flyrock related injury is sustained when a blast propels rock beyond the blast area and it injures someone. The primary factors for flyrock are:
• insufficient burden,
• improper blasthole layout, loading, and powder factor
• anomaly in the geology and rock structure,
• insufficient stemming, and
• inadequate delay time (hole to hole or row to row).
Nonmetal Mine, Johnson County, IL: On July 18, 1989, a plant foreman was fatally injured when
flyrock struck the roof of his 1987 Chevrolet C-20, 3/4-ton pickup truck [MSHA 1989b]. The impact
caused the roof to bend downward and strike the foreman’s head.
Twenty-five holes in five rows, on a 10- by 16-ft pattern, in sandstone overburden, were loaded with
6,550 lb of ANFO. Blast holes were 50-ft deep and 5-in diameter. The top 10 ft was stemmed with
The victim was in a pickup truck near the entrance to an access road to the blast site. Upon firing the shot, a sandstone rock weighing 8.5 lb and measuring 8- by 5- by 3-1/2-in, traveled 1,050 ft and hit the roof of the cab.
Causes/prevention: In this flyrock incident, the MSHA investigation report did not indicate which
factors caused this unusual flyrock. There was no evidence of misaligned boreholes, presence of voids or fissures in the limestone rock, or overloading of explosive charge. It is difficult to go back and reconstruct the circumstances leading to this incident.
Nonmetal Mine, Livingston County, IL: On July 11, 1990, flyrock from a limestone quarry traveled
about 930 ft and fatally injured a resident who was mowing grass on his property [MSHA 1990b].
Limestone was mined from a single bench by drilling and blasting.
On the day of this incident, thirty-six holes in three rows, twelve holes per row, were loaded with 2,556 lb of ANFO. The holes were 4-3/4-in diameter and 21-1/2-ft deep. The spacing and burden were 13-1/2 and 9 ft respectively. The upper 5 ft of each hole was stemmed with drill cuttings and crushed stone.
One of the holes near the center of the front row used an additional 18 to 25 lb of ANFO. The blasterdid not consider this unusual. A 70-ft high pile of rock and dirt was between the blast site and the victim’s property.
Walker County, AL: On September 22, 1990, flyrock projected from a surface coal mine
blast fatally injured the owner of a logging company [MSHA 1990c]. He was in the process of
preparing access roads for future logging operations and was outside the mine property.
Fifty-four holes, in six rows, 9-in diameter, 40-ft deep, on a 18- by 18-ft pattern were loaded with
emulsion explosive. Each hole contained about 864 lb of explosives. The stemming length was 10 ft.The pit area was cleared and the shot was fired. The blast projected flyrock about 900 ft and fatally injured the victim. Several large boulders were scattered near the accident site.
Mingo County, WV: On February 1, 1992, a blaster was fatally injured in a surface coal
mine by a 1-ft 5-in by 2-ft 11-in by 8-1/12-in flyrock [MSHA 1992]. The blaster positioned himself
under a Ford 9000, 2-1/2-ton truck while detonating the shot. A flyrock traveled 750 ft and fatally
injured the blaster. The mining company used a blasting contractor for loading and firing the shots.
Campbell County, TN: On June 4, 1993, a 16-year-old passenger, in a car driven by his
parent on interstate 75 (I-75), was fatally injured by flyrock originating from an overburden blast in a nearby coal mine [Shea and Clark 1998]. The closest blasthole was within 75 ft of the Right of Way and 225 ft from the I-75 pavement. This blast generated a large amount of flyrock. The I-75 traffic was not monitored prior to the blast.
The fatal blast was not designed according to the specifications approved in the permit document [Sheaand Clark 1998]. Instead of decking the explosive charges in two columns and priming separately, the entire charge was loaded in one column. Hole diameter and blast pattern used in this blast were different from the approved plan. The stemming was insufficient and the I-75 traffic was not monitored [Shea and Clark 1998]. The blaster, apparently, was unaware of the presence of an 8-ft thick layer of clay on the top of the sandstone overburden. Loading of explosives near the collar zone in unconsolidated material was considered a contributory factor.
Nonmetal Mine, Lancaster County, PA: On December 21, 1999, a 32-year-old equipment operator
was in a pickup truck guarding an access road to the blast site [MSHA1999b]. The pickup truck was
about 800 ft from the blast site. Flyrock entered into the cab through the windshield and fatally struck the victim. The mining company used a drilling contractor.
The major causes of blasting-related injuries in surface mines are lack of blast area security, flyrock, premature blast, misfire, and disposal. Inadequate size of the blast area, flyrock, and lack of blast area security (including lack of blasting shelter) accounted for 68% of the injuries. IME has defined flyrock as the rock(s) propelled from the blast area by the force of an explosion. Fragmented rock is not expected to travel beyond the confines of the blast area. An injury due to flyrock may be sustained when it travels beyond the blast area. The main causative factors responsible for propelling flyrock beyond the blast area are insufficient burden, improper blasthole layout and loading, anomaly in the geology and rock structure, insufficient stemming, excessive powder factor, inadequate firing delays, and inadequate size of the blast area. Injuries due to lack of blast area security were primarily caused by: failure to evacuate the blast area by employees and visitors; failure to understand the instructions of the blaster or supervisor; and inadequate guarding of the access roads leading to the blast area.