Shad, Call me and I can get you some prints on building it

Anything the produced water touches will have to be coated. Most are done with threads and Victaulic couplings. Some of the water is so bad they can cause leaks in less than a month on sch 80. The specifications should tell you what type of fittings to use and the drawings should show the tank lay out. Most of these installations will have a supply house like MJR or Wilson put a fitting trailer on the site and the client gets charged by what gets taken out of the trailer.
Be careful the crew is not building another facility on the side with your trailer. When the project is done they will do a fitting count and you better be really close on what came out of the supply trailer and what gets put in on the construction.

A lot will depend on what kind of volume they are expecting,how much of that volume they presume will be oil, and how far the will have to pump to the disposal well. We hook them up from gathering tanks to the well including pulsation control. One word of advice ( if they aren't just building it to sell it) run stainless on all your lower branch lines connecting your tanks on the gathering side and sending side. It will last longer than coated steel pipe or even fiberglass plus once you add up the cost of coated pipe vs sch 10 stainless it's not much more.