Would definitely ask permission, it's private property, expensive heavy equipment (sometimes stolen or tampered with). Never know, might get lucky, but construction guys don't usually like seeing people wandering around the site, that aren't involved with the project. It's not near one of those 'historical' areas? Historical finds, can be a real project killer, or at least cause delays, and lost bonus money. Would steer clear on using 'historical', 'relic', artifacts', or anything that might give the impression you are from a local university... Sounds like a big project, thinking low probability they will be receptive. Never know though, lots of people in the hobby these days...