The discussion of unexploded ordinance on the slopes of Sylvan Pass in Yellowstone National Park left over from avalanche control efforts seems to emerge every couple years. The truth is, Park officials don’t know where or how many there are, but assures they pose no threat to the visiting public. Years ago, people hiking Teton Pass near Jackson turned up howitzer shells that had failed to explode – but since the installation of Gazex® exploders, the need to bomb the avalanche-laden slopes there was all but eliminated. However Yellowstone Spokesman Al Nash says such devices are not likely to be built on the Yellowstone pass. He says explosives are usually delivered by a howitzer there, but the park has also dropped explosives on the avalanches from a helicopter. Still, some explosives fail to go off and end up lying on the mountainside, and while they have turned up on rare occasions, he says they are not likely to be accidentally turned up by visitors to the park. He says they have been found on rare occasion over the past years, but it is a place people drive through and not an area that people use for hiking or climbing. Nash says the avalanche control is staged not only to keep the pass safe for winter access from the East entrance, but to enable the route to be opened in the springtime.