What's your guess?
Look up while you are searching. What is the purpose of those large orange balls? Are they floats for utility lines? Are they part of an alert that there is a problem if they need to float? Is their purpose to scare off birds or to prevent them from nesting under the bridge like the peregrine falcons do under the Veterans Memorial Bridge downriver?
Update: oldmillcarl pointed me to the article in LNP by The Scribbler (Jack Brubaker) who asked the Columbia borough manager. The balls keep the electrical wires from running into each other during high winds. Screenshot of article from 3/22/2017 in gallery.
Hide is fairly obvious. In winter, it's easily visible if you are looking. But most people won't look here, so it should be safe. Be stealthy if you have company. I went with the "float" theme. Bring your own pencil.
Congratulations to MidnightsRaiders on the First-To-Find.