You generally need monitoring at a minimum, and maintenance to shore up degradation of any unstable containment materials (i.e. those used to prevent water leeching, etc).

Plus security. You need to keep people out- there's always going to be some idiot who wants to get too close or use it for Evil.

That said, I imagine the costs are far less than the alternatives. Rebuilding the grid to satisfy continental-wide wind will produce a lot of CO2.