Yep, give it a looksee and then you won't kick yourself when they pour the foundation and you hear through the grapevine that an old picnic ground used to be in that same spot. It shouldn't take long to determine if it's worth hunting. Give it a try!!! Then fill us in if you find anything.
If the site ever had previous activity I would try it. If the building is just being built in an open field that never saw any activity then there probably won't be much to find. My moto is: "If in doubt, detect" All you have to loose is your time.
Good luck!
Do what I call a detecting recon. Take a diagonal path across the field with descrimination set high. If you find an old coin, slow down and search that area hard. If it's producing, begin an organized thorough search. Turn the descrimination down as low as you can depending on the trash. You never know, I think back to some killer finds in the oddest of places.