The project for flood control on the Santa Ana River Mainstem, including Santiago Creek and Oak Street Drain, is adopted and authorized substantially in accordance with the recommendations of the Chief of Engineers Conference Report No. 99-1013 99th Congress, as adopted and authorized by the act of Congress approved October 17, 1986 (Public Law 99-662, the Water Resources Development Act of 1986), at an estimated cost to the state of the sum that may be appropriated for state cooperation by the Legislature upon the recommendation and advice of the department.