Upon not less than two years’ notice in writing from the commission the United States shall have the right upon or after the expiration of any license to take over and thereafter to maintain and operate any project or projects as defined in section 796 of this title, and covered in whole or in part by the license, or the right to take over upon mutual agreement with the licensee all property owned and held by the licensee then valuable and serviceable in the development, transmission, or distribution of power and which is then dependent for its usefulness upon the continuance of the license, together with any lock or locks or other aids to navigation constructed at the expense of the licensee, upon the condition that before taking possession it shall pay the net investment of the licensee in the project or projects taken, not to exceed the fair value of the property taken, plus such reasonable damages, if any, to property of the licensee valuable, serviceable, and dependent as above set forth but not taken, as may be caused by the severance therefrom of property taken, and shall assume all contracts entered into by the licensee with the approval of the Commission. The net investment of the licensee in the project or projects so taken and the amount of such severance damages, if any, shall be determined by the Commission after notice and opportunity for hearing. Such net investment shall not include or be affected by the value of any lands, rights-of-way, or other property of the United States licensed by the Commission under this chapter, by the license or by good will, going value, or prospective revenues; nor shall the values allowed for water rights, rights-of-way, lands, or interest in lands be in excess of the actual reasonable cost thereof at the time of acquisition by the licensee: Provided, That the right of the United States or any State or municipality to take over, maintain, and operate any project licensed under this chapter at any time by condemnation proceedings upon payment of just compensation is expressly reserved.
In any relicensing proceeding before the Commission any Federal department or agency may timely recommend, pursuant to such rules as the Commission shall prescribe, that the United States exercise its right to take over any project or projects. Thereafter, the Commission, if its  does not itself recommend such action pursuant to the provisions of section 800(c) of this title, shall upon motion of such department or agency stay the effective date of any order issuing a license, except an order issuing an annual license in accordance with the proviso of section 808(a) of this title, for two years after the date of issuance of such order, after which period the stay shall terminate, unless terminated earlier upon motion of the department or agency requesting the stay or by action of Congress. The Commission shall notify the Congress of any stay granted pursuant to this subsection.