The Environmental Protection Agency (EPA) is approving a State Implementation Plan (SIP) revision submitted by the State of New Hampshire. On July 29, 2021, the State submitted its 1997 ozone national ambient air quality standards (NAAQS) Limited Maintenance Plan (LMP) for the Boston-Manchester-Portsmouth (Portsmouth) area. EPA is approving the Portsmouth area LMP because it provides for the maintenance of the 1997 ozone NAAQS through the end of the second 10- year portion of the maintenance period. The effect of this action will be to make certain commitments related to maintenance of the 1997 ozone NAAQS in the Portsmouth maintenance area part of the New Hampshire SIP and therefore federally enforceable. This action is being taken in accordance with the Clean Air Act.