A community of agents decide to provide itself with a noxious facility. To do so, they call on a firm that will be in charge of the siting and the construction of the facility. In such a context, the firm propose a siting/pricing mechanism to the community. Under incomplete information, we show that optimal mechanisms facilitating the siting and pricing of the facility exhibit allocative inefficiencies due to the informational rent given to each agents. In two cases drawn from the general cases (diffuse extenailities and local externalities), we fully characterize the optimal auction.