The Cortese-Knox-Hertzberg Local Government Reorganization Act of 2000 (CKH Act) was adopted by the State legislature to establish procedures for the orderly growth and development of counties and cities (Government Code (GC) §5600-57550). Each County within California is required to establish a Local Agency Formation Commission (LAFCO) for regulating orderly growth and development by (1) discouraging urban sprawl, (2) preserving open space and prime agricultural lands, (3) encouraging the efficient provisions of government services, and (4) encouraging the orderly formation and development of local agencies based on local conditions and circumstances. Each City within each County is responsible for developing a probable plan that outlines future growth in accordance with an adopted General Plan. This probable plan is called a Municipal Services Review (MSR), and the maximum extent of that growth is defined by the City’s Sphere of Influence (SOI).

The Solano County LAFCO is responsible for reviewing and approving the SOI for each City in Solano County, which must be completed on a regular basis occurring every five years, or as necessary. Any changes or reorganizations to an SOI must be based on specific criteria (GC §56425(e)) disclosed within the MSR with supporting information about the City’s remaining inventory of residential land within the current SOI. The last MSR and SOI was adopted by the Solano County LAFCO on May 8, 2017.  On March 11, 2025, the Vacaville City Council directed staff to start the process for preparing a comprehensive update to the Vacaville MSR to support any reorganizations to the SOI boundary.