Create a cover story for something that needs a lot of the same resources: huge amounts of underground excavation, many miles of superconductive magnets and infrastructure for same, computing resources, etc. That sounds like a collider, but on an unprecidented scale: a superconductive super collider! You also choose a site good for underground chamber making and free from seismic activity, just as for building a collider.
People see the published (cover) specs, and see how much chalk and shale is coming up, and assume that you are making a huge circle tunnel, but a large chamber with several small tunnels have the same volume of digging. Be sure to design in an access hatch by which a huge wheel-shaped instrument can be lowered later.
Then, when money is spent and the needed work is done, you cancel the project. You skip hooking up the huge power feed to the huge intake you built, never running power lines into the area, so people assume the site really is dead—nobody knows about the off-the-grid Naquadah reactor.
The newly discovered high-temperature superconductor material — this “invention” had to be leaked to general scientific community in order to provide for industrial quantities to be manufactured — turned out to be fatally flawed for the supercollider usage, as it is not only brittle but can't handle the stress of the magnetic field it was made for. This fiasco was the very excuse for cancelling the project with such high sunk costs, and everyone in the scientific community can see for themselves that it is true and repeatable: they crumble like dry soda crackers, and only handle a fraction of the magnetic strength predicted in theory and extrapolated from small samples.
But, it is all a ruse. The use case is actually different from what the public thinks, and a stabilizing coating was kept secret and not revealed with the material proper. The 80 killometers of superconductor is safely stashed in the hole, refit to its real purpose.
So, I conclude that the place to put the stargate command is near Waxahachie Texas.
Finally, as a disinformation campaign to camouflage and repudiate leaks, create a TV show with the same rough premise, but campy and differing in actual detail, including the use of a high-profile location for the command center.
it would need a lot of energy, and we have no other alien technology, other then the stargate itself.
The original plan was to use a reactor from an aircraft carrier, with additional cover stories about “loosing” one. But small Naquadah generators were discovered on early missions and easily scaled up.
[cover for] An alien Invasion by the Goa'uld
People already run around in strange costumes, and this started in 1981. This was just 2 years before the SSC project was publicly endorsed, about the time it was first planned as a cover. In fact, it was itself a cover story for a camp of relocated offworlders living with medeval technology. The newspaper was told “oh, they're re-enactors (or larping)” and everyone decided to join in. The large movement of people through the normally rual area was an initial lure to do more project-related activities there.