Defines the Rim of the Valley Unit boundary by reference to two specific maps, requires those maps to be on file and available to the public, and lets the Secretary make minor boundary adjustments after notifying two congressional committees and publishing the change. Any land the Department of the Interior acquires inside the Unit must be managed as part of the Santa Monica Mountains National Recreation Area under the laws and regulations that govern that national recreation area. The bill also preserves existing operation, maintenance, and modification of water resource facilities and public utilities within the Unit, while requiring that such activities reasonably avoid or reduce harm to the Unit’s natural and cultural resources.