Updates the boundary of the Santa Monica Mountains National Recreation Area to include the Rim of the Valley Unit by adopting new official maps, requires those maps to be available for public inspection, and allows the Secretary of the Interior to make limited boundary tweaks with committee notice. Lands or interests in lands acquired inside the Rim of the Valley Unit will be managed and administered as part of the National Recreation Area under existing laws and regulations. The change preserves the operation, maintenance, and modification of existing water resource facilities and public utilities within the Unit, while requiring such activities to reasonably avoid or reduce harm to the Unit’s natural and cultural resources.