Pros
Very good job security, excellent union (at least in the location I was at). Good as a starter job to get some years experience under your belt as a Planner or Biologist so you can hop to a more fulfilling job later.
Cons
It's incredibly soul-sucking to work here as a biologist. You're working on the side of the highway at all times and are often told to minimize any environmental concerns you have for the sake of staying on schedule with construction. As other reviewers have mentioned it is an engineer's company and the engineers get priority for everything. Biologists get barely functional working tools, outdated safety tools and precautions, very little resources, and are still expected to take on 15-20 projects simultaneously and with very little training. I've seen so many people burn out at this job because of this. Finally, from the perspective of a biologist it feels like you are really just a formality for Caltrans. It often feels like you're just there to check a box with state and federal agencies so that construction can begin. You aren't a scientist in this position. Things move incredibly slow, full of red tape. Very low retention of biologists because once you have the minimum experience needed for an actual scientific job where you're treated like a priority, why stay at a government construction agency?