California Code, Public Resources Code - PRC § 43507

The owner and operator shall, regardless of any changes occurring during the continued operation of the landfill, close and maintain the landfill during postclosure in accordance with the most recent closure plan and the most recent postclosure maintenance plan approved by the board pursuant to this article.  Upon receipt of the final shipment of solid waste, the most recent closure and postclosure maintenance plan shall become the governing document for the disposal site.