In an effort to achieve a delicate balance between preserving resources, protecting visitors, and supporting an historic way of enjoying Glacier National Park, park officials on occasion find it necessary to use explosives to open trails in the summer.
The small hand charges are strategically placed to create treads across snowfields slow to melt. Usually only three areas require such help: the trail to Ahern Pass, Ptarmigan Tunnel, and the Highline Trail, says Jack Potter, the park's supervisory biologist.
Running north of Logan Pass to the Granite Park Chalet, the Highline Trail lies directly below the Garden Wall that rises along the Continental Divide. Not surprisingly, the trail is frequently buried deep under snow come summer. Relying only on warm weather and sunshine to clear the snow would severely impact the chalet's short summer season, says Mr. Potter.
“We’ve been doing that since 1925," he says of the use of explosives to clear trail paths through deep snows. "If they leave them, that means that you could take a 50-mile loop and have to have ice axes or crampons for about 50 yards of snow.
“So, what they used to do is do that extensively in more places and do it all the time. I remember when I first started on the trails crews ... we would start in late June and spend weeks doing this blasting, and only to get it open a couple weeks earlier so the concessionaire wouldn’t complain that he couldn’t get his people up there," recalled Mr. Potter.
Crews determine what areas to blast by surveying how extensive snowfields are in the early summer. While Mr. Potter couldn't specify a distance -- "There are some benchmarks, visual, that they use to say, 'This is possible, this isn’t possible,' and that’s what’s used to make those determinations.” -- he said if a half-mile of snow was covering the trail they wouldn't attempt to clear a path through it.
Once a decision is made to blast, the work is fairly straightforward, he said, and quickly done when compared to clearing a path by hand.
"The problem with doing it all by hand is that you’d have to go on a daily basis. Chopping the steps doesn’t work as well," said Mr. Potter. "So when you use a little bit of explosives that they use, it makes a tread that generally will last for the duration until it melts.
“You dig some holes, and put in some explosives. And when they blast they create a surface to walk on that’s almost five feet wide. And that will last. You won’t have to go back up and shovel it again.”
In January 2009 Glacier officials issued a biological assessment (attached) that looked into the use of explosives in the park and how they might affect wildlife. The explosives -- usually ammonium nitrate and fuel oil -- come into play for clearing trails of landslides or rockfalls, as well as deep snow, and digging holes for backcountry pit toilets.
(Another use is to, essentially, vaporize carcasses of wildlife or pack animals that die along or near trails so they don't lure bears. In Dinosaur National Monument, master blasters for the Park Service somewhat delicately removed a layer of rock with explosives to help paleontologists reach a fossil.)
In their assessment, Glacier's managers determined that blasting at times might be performed in areas of the park known to lie within the habitat of lynx, a threatened species; in areas used by gray wolf, an endangered species, for denning and rendezvous sites, and; in areas frequented by grizzly bears, a threatened species. In each case, the assessment concluded that blasting work might affect, but was not likely to adversely affect, any species.
And yet, the assessment also acknowledged that "(I)n general, wildlife respond to explosives use but little is known about the extent, duration, or intensity of response, especially for carnivorous mammals. Behavioral and physiological responses to explosives use may result in accidental injury, reproductive loss, energy loss, habitat avoidance and abandonment."
Mr. Potter, who can count 33 years of either working on or overseeing trail maintenance crews in Glacier, said he couldn't recall any negative conflicts between the blasting and wildlife.
"Most animals look over and then go back to whatever they were doing," he said. "It’s not very loud in the sense that there’s thunderstorms that rumble through all the time. So these fixed isolated events of a blast, they don’t really scare the animals."
In fact, years ago when other types of explosives were used the blasts were akin to dinner bells for mountain goats, the biologist said.
"The biggest problem we used to have was when we had the explosives that still had salt residues in them back in the old days," said Mr. Potter. "The goats would come running and lick up the residue. That was not a pretty sight. They would hear the blast and come charging from all over the place.
“I was working at Gunsight and they would be on that stuff in about two seconds. And they’d be licking it like crazy. Now, the Park service doesn’t even use those types of explosives any more."
This practice might seem in direct conflict with the Park Service's decision in 2008 not to allow Burlington Northern Santa Fe Railroad to lob explosive charges into avalanche chutes on the park's southern boundary to prevent slides from blocking the tracks that run along that boundary.
However, points out Mr. Potter, the use of explosives in the two situations are greatly different. “What the railroad wanted to do was this sustained blasting program up in the winter range with the idea being to generate shock waves," he said.
So while the railroad's intent was to create loud explosions with powerful shock waves to trigger avalanches, with trail maintenance the blasts are focused and designed to move small areas of snow, he said.
"You’ve got these very short sections of trail where if you blast them, you increase by two to three weeks the time that people who don’t have specialized equipment -- ropes, ice axes, crampons -- can go across them," Mr. Potter explained. "That’s it. That’s the reason.”
Now, there are other areas in the National Park System where travel across snow can be dangerous -- the approach to the Lower Saddle of the Grand Teton in Grand Teton National Park is one -- but the biologist pointed out that your typical park visitor who's heading to the Lower Saddle is much more accomplished and equipped for snow travel than the visitor heading to the Granite Park Chalet.
"You’re getting people who are of a much different class of skill," he said.