The Environmental Protection Agency (EPA) is approving a State Implementation Plan (SIP) revision submitted by the State of New Hampshire. This SIP revision establishes carbon monoxide (CO) limited maintenance plans for the City of Manchester, New Hampshire and the City of Nashua, New Hampshire. As part of its limited maintenance plan, New Hampshire will continue year-round CO monitoring at the Londonderry Moose Hill station in Londonderry, New Hampshire with triggers to reestablish CO monitoring sites in Manchester and Nashua if elevated CO levels are recorded in Londonderry. Future carbon monoxide transportation conformity evaluations for Manchester and Nashua will, for the length of their limited maintenance plans, be considered to satisfy the regional emissions analysis and "budget test" requirements. This action is being taken under the Clean Air Act.