The structure to the right in the picture is in fact part of the old Canon City water pipeline, which was constructed of redwood staves held together with thousands of steel rings. The pipeline was 6 miles long and was in service until 1974 when it was replaced with a pumping station right in town, which is much easier to maintain.
A few other changes in the ensuing years since the picture was taken: the chain link fence is still there but has taken a beating from years of falling rocks and derailments. The grade has also been lowered through the Hanging Bridge area to improve clearances - the overhead spans on the Hanging Bridge were also raised for the same reason. This has resulted in the wall the fence is mounted on now being about a foot above the ties instead of even with them as in the picture. This has made the area almost useless as a platform like it once was. It did enable the SP to run double stacks on the Tenn. Pass route, though.
Phil