The Santa Ana River Mainstem Project (SARP) was initiated in 1964, in partial response to a resolution of the House Committee on Public Works adopted May 8, 1964 . A survey report was completed by the United States Army Corps of Engineers (USACE) Los Angeles District in 1975. The report was reviewed, then submitted to Congress in September 1978.
In September 1980, the USACE completed the Phase I General Design Memorandum (GDM) for the Santa Ana Mainstem. Construction of the SARP was authorized by Section 401(a) of the Water Resources Development Act of 1986. Construction of SARP was initiated in 1989, and completion is scheduled for 2020.