1. Below ground, except where control and pumping equipment come into play. Below the permafrost line, so it varies.
2. Usually they pay "rent" to a landholder. Eminent domain comes into play, but usually they try to negotiate before that happens. It gets costly in court for both side.
3. Not just shutoff valve but pump stations. And all of this infrastructure needs to be maintained. And the equipment gets sent out for repair. Lots and lots of jobs doing all of this.