My day job has always been in construction. I had a non- union buiilding and restoration business and now I'm a field engineer and work on mostly union projects. The independant, non-union business often doesn't have the resources to work with or the knowlege, but we were always putting safety first.
I have to say that Union jobs are really focused on worker safety and a problem only seems to come up when someone Screws Up or an act of nature...not because the site wasn't safe.
I know from experience though that you NEVER know when a trench will let loose... so shore it up !