It was at this point where the Oregon and Northwestern Railroad line from Burns to Seneca passed through a short tunnel. The railroad ceased operations in 1984 but the tunnel (although barricaded from entry) remained until roughly 1996, when the Forest Service permanently closed the hole due to liability concerns.
The cache is a short sidetrip west off Highway 395 on the paved Forest Road 31, then a short jaunt to the cache. Winter access could be tricky. You're looking for a camoed plastic container.