The Secretary of the Army, acting through the Chief of Engineers, may, when he determines it to be in the public interest, enter into agreements providing for reimbursement to States or political subdivisions thereof for work to be performed by such non-Federal public bodies at water resources development projects authorized for construction under the Secretary of the Army and the supervision of the Chief of Engineers. Such agreements may provide for reimbursement of installation costs incurred by such entities or an equivalent reduction in the contributions they would otherwise be required to make, or in appropriate cases, for a combination thereof. The amount of Federal reimbursement, including reductions in contributions, for a single project shall not exceed $5,000,000 or 1 percent of the total project cost, whichever is greater; except that the amount of actual Federal reimbursement, including reductions in contributions, for such project may not exceed $7,000,000 in any fiscal year.