Left Over From Blasting During Construction?

Out along the Sumpter Valley Ry. mainline and on Baker White Pine Lumber Co.'s Curry Line there are places where you can see scattered black powder cans such as this. Complete cans are getting to be rare both from deterioration in the elements and from ones with nice stamped lettering on the ends being harvested. This photo was taken in 1981. The caption on the back does not give the location, but says they were left from blasting out snow drifts. The locations where I have seen them are always adjacent to cuts, so I guess this is possible, but my assumption has been that they were left from the actual construction where black powder was used to break up the granite rock encountered. The scan is from the SVRR Archive.