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Explosives!

A specialized mining tool


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It’s not surprising that the federal government has a few regulations regarding the use of explosives in mining: 30 CFR, Part 15 (approval of explosives and sheathed explosive units); 30 CFR Part 56, Subpart E (safety and health standards: surface metal and nonmetal mines: explosives); 30 CFR Part 57, Subpart E (safety and health standards: underground metal and nonmetal mines: explosives); 30 CFR Part 75, Subpart N (mandatory safety standards: underground coal mines: explosives and blasting); and 30 CFR Part 77, Subpart N (mandatory safety standards: surface coal mines and surface work areas of underground coal mines: explosives and blasting) cover the bulk of it.

National entities such as the Mine Safety and Health Administration, the Environmental Protection Agency, the Bureau of Alcohol, Tobacco, Firearms, and Explosives, and the Office of Surface Mining Reclamation and Enforcement all have a part in ensuring that explosives used above or below ground in the pursuit of any commodity are handled in a way that is safe for workers and the environment.

 

Regulating Risk

And then on the state level, the Alaska Department of Labor and Workforce Development also has input as to who blows up what (and when and how).

One significant requirement at the state level is that “all employees doing excavation, tunnel, quarry, earth removal, or construction work, and who are emplacing explosives for detonation, installing primers, fuses, wires, or other means of detonation, or detonating explosives, are required to obtain a certificate of fitness for explosive handlers.”

This certificate is granted only to an individual (not a company or organization) who is over the age of eighteen and “is found competent by reason of training, experience, criminal history and background check, and physical fitness.” That individual then needs to have the certificate on his or her person whenever handling explosives.

A certificate of fitness is valid for three years, but may be cancelled at any time “for cause” by the Department.

Turns out, explosions can be high risk.

Those risks differ from site to site. According to the US Centers for Disease Control and Prevention, “Detonating explosives release toxic gases, primarily oxides of nitrogen and carbon monoxide. Nitric oxide (NO) and nitrogen dioxide (NO2) are produced by large surface blasts in which the explosive does not detonate properly. NO released by the detonation oxidizes to NO2 as the fumes mix with the atmosphere…NO2 is extremely toxic.

“Carbon monoxide (CO) is also released by the detonation of explosives. CO is not a problem after large surface blasts because it quickly dissipates in the atmosphere to safe levels. CO dangers are more of a problem for construction, trench, and underground blasting. If a mine worker walks onto a blast site too soon after a blast, the CO emanating from the muck pile poses a serious risk to the worker.” In the United States, between 1994 and 2005, eight miners were injured by exposure to blasting fumes.

During that same time period, sixty-eight miners were injured because they were within the “blast area” (the area in which rocks are expected to fly) during an explosion and thirty-two miners were injured by “fly rock” (rock or debris flung outside a blast range), according to Centers for Disease Control and Prevention data.

Optimally accidents such as these never take place, but considering the breadth mining activity in the United States, those numbers are low. According to the National Mining Association, in 2017 there were 311,888 mine workers in the United States and 523,034 direct jobs created by the mining industry.

In 2017, of those 523,034 jobs, 4,500 were in Alaska, and the Mine Safety and Health Administration reports only one fatality related to blasting in Alaska between 2008 and 2018.

Alaska’s operating mines implement stringent health and safety guidelines to ensure every employee gets home safe every day. Day in and day out, local mines successfully navigate a range of potential risks, of which handling and deploying explosives is just one.

And explosives are a valuable tool.

According to Paul Worsey, in an interview by Chris Lo for Mining Technology, “Explosives are very important because it’s the only really economic way to break up hard rock… Not only have you got to break it up so you can load it into trucks, it also has to be of a size that you can process easily.

“That said, probably the majority of explosives in the US is used for overburden removal in surface coal mining. We mine more than one billion tons of coal every year, and the vast majority of that is from surface operations. If you’ve got coal in a surface, you’ve usually got shales and siltstones on top of it, and you have to blast to get at it.”

 

Explosives in Alaska

Usibelli Coal Mine (UCM), the only coal mine currently operating in Alaska, “uses explosives when overburden or coal needs to be broken in order to excavate or mine it,” according to Lorali Simon, UCM vice president of external affairs. Primarily UCM uses ammonium nitrate/fuel oil (ANFO), a widely-used bulk industrial explosive, combined with boosters and non-electric or electric detonators. “UCM uses explosives by drilling holes into the sandstone or coal, loading those holes with explosives, and then initiating the blast from a safe location,” Simon says.

On average UCM blasts overburden (the layer of earth material on top of a coal seam) or coal once or twice a month.

Simon explains there are pros and cons to using explosives as part of the mining process. They increase efficiency by increasing the digging rate and save wear and tear on mining equipment by reducing the hardness of the material; however, there is an added cost to acquire the explosives, and “it requires special training for all involved employees and added record keeping and permitting requirements.”

Wendie MacNaughton, the external affairs manager for Sumitomo Metal Mining Pogo, also says explosives add to efficiency. But she adds, “There is large effort in planning, control of materials, and staying current on safety and regulatory requirements. Explosives can generate ground vibration or noise (air blast)—so there are special controls and communication required to avoid problems with mine neighbors.”

Pogo is an underground gold mine, and the explosives are used to break up solid rock that can’t be efficiently excavated by heavy equipment. MacNaughton explains that “explosives can be bulk slurry material (pumped from truck hauled tanks) or solid cartridges (from fifty-pound boxes) that are handled individually—two pounds per ‘stick.’ Bulk explosives require high energy caps to initiate them.” Caps, also referred to as detonators, are handled separately and then combined with bulk explosive in individual drill holes, she says.

At Red Dog, one of the world’s largest zinc mines, explosives are used on a daily basis to fracture rock so it can be excavated and hauled out, according to Laura Orenga de Gaffory, community relations coordinator for Teck Alaska. “Explosives are loaded into 6.5-inch holes that are approximately 30 feet deep, arranged in a geometrical pattern designed to optimize the rock breakage. Since the rock at Red Dog is largely considered hard, nearly all of the material mined required blasting in order to excavate. The rock must be blasted to a small enough size to A) be excavated by front end loaders into haul trucks and B) be small enough for the Gyratory crusher if it is mineralized ore,” she explains. The crusher reduces larger rocks to less than five inches in size, the size required for milling.

De Gaffory continues: “Red Dog employs modernized electronic initiation and delay systems from Orica to control the detonation timing and orientation of blast hole patterns. In so doing, aspects such as fly rock, air blast, and vibration are controlled in order to avoid unwanted collateral damage to infrastructure or the final walls of the pit(s). The system works well enough that technical staff are able to separate material in different directions by initiating a blast in a particular fashion.”

De Gaffory says explosives are “wholly necessary in the mining process at Red Dog,” though buying and transporting them does add cost, as does the need for specialized equipment and permitting.

 

Suppliers

Red Dog uses Orica systems but sources explosives from Maxam, founded in 1979 and headquartered in Salt Lake City, Utah. Maxam is a worldwide manufacturer and distributor of commercial explosives, as well as technical services. The company states, “In 1981, Maxam North America introduced an advanced explosives system to the mining industry based on HEF-High Energy Fuel, which when blended with ammonium nitrate prills forms Heavy ANFO. Heavy ANFO has significant water resistance, higher density, and greater energy than ANFO.”

UCM sources its explosives from Orica, an international provider of commercial explosives and blasting systems. The company was founded in 1874 and has 11,500 employees across the globe. It says: “Our strategy is to be the trusted partner of choice for our customers by creating, developing, and delivering mining and civil blasting and ground control solutions that help them be more productive and manage their critical risks.” The company’s range of products includes electronic blasting systems, initiating systems, packaged explosives, and blasting services.

Locally, Advanced Blasting Services is a “comprehensive drilling and blasting contractor/subcontractor,” headquartered in Anchorage. Advanced Blasting Services has completed jobs in “every climate and condition encountered in Alaska,” and maintains “a perfect safety record after years of blasting in residential areas and close to existing buildings and utilities,” it says.

 

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