When a requirement develops for a new installation or the extension of an existing installation, site selection will be the primary responsibility of the using service. A representative of the appropriate Division or District Engineer will participate in selection of sites for the Department of the Army and, upon request, in Department of the Air Force site selection and preliminary investigations. Commanders and site boards should be informed of any available lands, including marginal lands in civil works projects and available lands under the control of other departments and agencies, suitable for the desired purpose. The using service will request the Chief of Engineers or the appropriate Division or District Engineer to prepare a Real Estate Planning Report or Real Estate Summary, making reference to the prior Site Selection Report if one was prepared.