This action finalizes the residual risk and technology review (RTR) conducted for the Primary Aluminum Production source category regulated under national emission standards for hazardous air pollutants (NESHAP). In addition, we are taking final action regarding new and revised emission standards for various hazardous air pollutants (HAP) emitted by this source category based on the RTR, newly obtained emissions test data, and comments we received in response to the 2011 proposal and 2014 supplemental proposal. These final amendments include technology-based standards and work practice standards reflecting performance of maximum achievable control technology (MACT), and related monitoring, reporting, and testing requirements, for several previously unregulated HAP from various emissions sources. Furthermore, based on our risk review, we are finalizing new and revised emission standards for certain HAP emissions from potlines using the Soderberg technology to address risk. We are also adding a requirement for electronic reporting of compliance data, eliminating the exemptions for periods of startup, shutdown, and malfunctions (SSM), and not adopting the affirmative defense provisions proposed in 2011, consistent with a recent court decision vacating the affirmative defense provisions. This action will provide improved environmental protection regarding potential emissions of HAP emissions from primary aluminum reduction facilities.