Turn north off the highway onto Finnmark Rd. The more maintained road turns into Flett Rd. A four way junction is actually where the old railroad came through. This has been turned into a logging road (although I don't think they are logging anymore).
Follow west and you will arrive at the old railway tunnel. It is driveable and in good condition. There is a parking/turnaround on the west side of the tunnel.
Container is a small brown lockable geo cache container. Getting an accurate GPS reading may be tricky as you get closer to the tunnel. The hint should prevent any frustration however.