After December 31, 1970, the construction of any water resources project, or an acceptable separable element thereof, by the Secretary of the Army, acting through the Chief of Engineers, or by a non-Federal interest where such interest will be reimbursed for such construction under the provisions of section 1962d–5a of this title or under any other provision of law, shall not be commenced until each non-Federal interest has entered into a written agreement with the Secretary of the Army to furnish its required cooperation for the project or the appropriate element of the project, as the case may be; except that no such agreement shall be required if the Secretary determines that the administrative costs associated with negotiating, executing, or administering the agreement would exceed the amount of the contribution required from the non-Federal interest and are less than $25,000. In any such agreement entered into by a State, or a body politic of the State which derives its powers from the State constitution, or a governmental entity created by the State legislature, the agreement may reflect that it does not obligate future appropriations for such performance and payment when obligating future appropriations would be inconsistent with constitutional or statutory limitations of the State or a political subdivision of the State.

A non-Federal interest shall be a legally constituted public body with full authority and capability to perform the terms of its agreement and to pay damages, if necessary, in the event of failure to perform.

Every agreement entered into pursuant to this section shall be enforcible in the appropriate district court of the United States.

After commencement of construction of a project, the Chief of Engineers may undertake performance of those items of cooperation necessary to the functioning of the project for its purposes, if he has first notified the non-Federal interest of its failure to perform the terms of its agreement and has given such interest a reasonable time after such notification to so perform.

This section shall not apply to any project the construction of which was commenced before January 1, 1972, or to the assurances for future demands required by the Water Supply Act of 1958, as amended [43 U.S.C. 390b].