June 2, 2011
Guard against highwall and stockpile incidents by staying aware of hazards, inspecting the areas, and controlling access to the areas.
By Tina Grady Barbaccia, News/Digital Editor
To keep your operation’s employees safe when working around and with stockpiles and highwalls, the Mine Safety and Health Administration (MSHA) offers five best practices:
• Be aware of overhanging material when loading from stockpiles and highwalls.
• Stay back from the edge and build a berm.
• Stay clear of draw points above surge tunnels.
• Always scale the highwall back.
• Never place yourself between the equipment and the stockpile or highwall.
“When looking at your pits, always look for berms on the backside,” says Pat Hayden, regional safety manager for Mountain States at Knife River. “Make sure no one is going to sneak into a pit. You don’t want a farmer or someone to come over the edge of your mine in the dark.”
On the backside of a highwall, berms must be kept in top-notch condition. “We have a 980 loader that is used to maintain a gravel berm about 3 feet high,” Hayden says. “You need at least that.”
In high-traffic area, signs should be erected to keep people out of the pit that do not belong there.
A good rule of thumb, Hayden says, is to keep people away from a highwall with the same height to distance ratio. “If you have a 20-foot highwall, people should never get within 20 feet of it,” Hayden notes.
Since 2007,MSHA reports that there have been no reported fatalities from falling off a face/rib/highwall in the metal-non-metal mining sector.
Employees also need to be aware of the highwall structure when loading from stockpiles and highwalls, especially overhanging material. “They need to watch out for material frozen in the top part of the highwall,” Hayden points out. “You can hit a frozen layer as you’re moving through the highwall. If it’s good gravel, it tends to just fall down as you mine it. But if it’s frozen or the ground has quite a bit of water in it, you could undermine the wall.”
If a highwall is visibly undermined, Hayden says, it may need to be pushed down with a loader. “The base is always going to have an alluvial plane,” he says. “Hopefully, there is material in the base.” Typically, a vertical edge cannot be seen, Hayden notes, adding, “You don’t want it to come down in a vertical piece. You want it to slough off. You hardly ever see a clean edge.”
When working close to the crest, MSHA emphasizes keeping a safe a distance because of a high potential for injury for unprotected employees in the fall hazard zone. Before an employee begins work, the highwall area should be inspected by a “competent” person. “This person goes out, evaluates the area, and determines if there are any issues,” Hayden says. “As a rule, it doesn’t matter that it’s required. You always need to look around your work area. If you have a major storm the night before, make sure highwall, guardrail, or berm conditions haven’t changed. Make sure they are still safe.”
Even if there hasn’t been a storm, when a highwall is being mined out, conditions are always changing, Hayden says. This needs to be noted. As part of the highwall inspection, he says, the person inspecting the area should ask, “What does this look like every day? Is it doing what it normally does?”
Moreover, special consideration must be given if the highwall is in an area where the potential exists for underground utilities or pipelines. “Make sure you also ask, ‘Do you have power or anything running in that highwall that, when you put your bucket in it, there could potentially be a hazard,’” Hayden suggests. He also advises calling in your “locates,” especially in a new pit. “All the huge pipelines in the United States run in the middle of nowhere,” he says. “It’s better to know what you have in the ground than be up against a potential hazard.”
Hayden recalls an incident several years ago — not at Knife River — where a mechanic backed off the highwall. “He went to work on a piece of equipment, but misjudged where he was,” Hayden says. The worker was uninjured, but the point is, Hayden says, “You need to always be aware of your surroundings.”
Knife River Corp., based in Bismarck, N.D., has several operations in the northern United States, where daylight hours can be short, especially during the winter months. “In the north, we work quite a bit in the dark, and the mechanics are always out there after hours,” Hayden says. “You always need to know where you are.” Always know your hazards. Discuss the hazards and how they can lead to an accident. Have there been past slips or trips near the highwall?
Even with lights on a crusher and a loader, “You really need to keep your bearings,” Hayden warns, adding that people not working on the equipment need to stay away from it. He suggests talking to someone on a radio instead of being out in the pit. “If you absolutely have to go down there, get visual contact, turn on your beacon, or flash your lights,” Hayden advises. And though it may seem obvious, Hayden reminds workers that they need to wear reflective clothing and hard hats. And if a person cannot accomplish a task by radio and absolutely must go out in the pit near the highwall or stockpile, “Do not go near the operator until he or she stops,” Hayden cautions.
When stockpiling with a loader, there needs to be good berms on either side of the roadway. “A good berm is mid-axle height of the largest piece of equipment traveling the roadway, according to MSHA law,” says Hayden. “This is the berm standard. All of the berms need to be mid-axle height of the largest piece of mobile equipment that usually travels the roadway.”
With the stockpiles themselves, the equipment operators need to ensure there is no slabbing. For example, if crushing is done in one place and then material is taken to another place, the stockpile will be long and thin with berms on both sides if a belly dump and blade are used. With all the trucks then driving over the top of the stockpile, the weight compacts it. “In these kinds of stockpiles, you can have slabbing,” Hayden says. “If large chunks of material collapse onto the loader bucket, it can raise the back of the loader or can pick you up if a loader of insufficient size is used. If you’re in the pit, it can fall down.” Hayden says a good rule to follow is, “If in doubt, push it down.”
Top tips for highwall and berm safety
Inspect, inspect, inspect. Build good berms, inspect them, and maintain them.
Control access to highwalls and stockpiles.
Be aware of your surroundings and control your hazards. Conduct examinations of the highwall before, during, and after every rain, freeze, or thaw.
Inspect your stockpile and berms. Inspect and evaluate them, and eliminate or control any hazards. Scale down loose, hazardous material, and do not work under loose material for any reason.
If it’s a new pit, call for your locates and know what’s in the ground. You don’t want to hit a major gas line or pipe line.
Pay special attention when working in the corners of box cuts.
Increase the number of benches at each highwall to catch falling material.
The Small Mine Office developed a series of weekly ToolBox talks that can be used by small mine operators and others to hold safety and health discussions for employees at their mining operations. These ToolBox talks were developed in consultation with members of the mining community. To get the free app, enter http://www.gettag.mobi into your browser.