(a) Approval - On February 1, 1999, the New Hampshire Department of Environmental Services submitted a revision to the State Implementation Plan to remove the Nashua Inspection/Maintenance program for carbon monoxide that ceased operating on January 1, 1995. The Nashua Inspection/Maintenance was originally approved at § 52.1520(c)(39). The Nashua Inspection/Maintenance program was replaced with controls consisting of the existing federal Tier 1 emission standards for new vehicles and the federal reformulated gasoline program.

(b) Approval - On February 2, 1999, the New Hampshire Department of Environmental Services submitted a request to redesignate the City of Manchester carbon monoxide nonattainment area to attainment for carbon monoxide. As part of the redesignation request, the State submitted a maintenance plan as required by 175A of the Clean Air Act, as amended in 1990. Elements of the section 175A maintenance plan include a base year (1990 attainment year) emission inventory for carbon monoxide, a demonstration of maintenance of the carbon monoxide NAAQS with projected emission inventories to the year 2010 for carbon monoxide, a plan to verify continued attainment, a contingency plan, and an obligation to submit additional information in eight years acknowledging that the maintenance plan will remain in effect through the year 2020, as required by the Clean Air Act. If the area records a violation of the carbon monoxide NAAQS (which must be confirmed by the State), New Hampshire will implement one or more appropriate contingency measure(s) which are contained in the contingency plan. The menu of contingency measures includes the enhanced safety inspection program and New Hampshire's low emission vehicle program (NLEV) as contingency measures. The redesignation request establishes a motor vehicle emissions budget of 55.83 tons per day for carbon monoxide to be used in determining transportation conformity for the Manchester area. The redesignation request and maintenance plan meet the redesignation requirements in sections 107(d)(3)(E) and 175A of the Act as amended in 1990, respectively.

(c) Approval - On February 2, 1999, the New Hampshire Department of Environmental Services submitted a request to redesignate the City of Nashua carbon monoxide nonattainment area to attainment for carbon monoxide. As part of the redesignation request, the State submitted a maintenance plan as required by 175A of the Clean Air Act, as amended in 1990. Elements of the section 175A maintenance plan include a base year (1990 attainment year) emission inventory for carbon monoxide, a demonstration of maintenance of the carbon monoxide NAAQS with projected emission inventories to the year 2010 for carbon monoxide, a plan to verify continued attainment, a contingency plan, and an obligation to submit additional information in eight years acknowledging that the maintenance plan will remain in effect through the year 2020, as required by the Clean Air Act. If the area records a violation of the carbon monoxide NAAQS (which must be confirmed by the State), New Hampshire will implement one or more appropriate contingency measure(s) which are contained in the contingency plan. The menu of contingency measures includes the enhanced safety inspection program and New Hampshire's low emission vehicle program (NLEV) as contingency measures. The redesignation request establishes a motor vehicle emissions budget of 60.13 tons per day for carbon monoxide to be used in determining transportation conformity for the Nashua area. The redesignation request and maintenance plan meet the redesignation requirements in sections 107(d)(3)(E) and 175A of the Act as amended in 1990, respectively.

(d) Approval - On May 30, 2007, the New Hampshire Department of Environmental Services submitted a modification to the Nashua maintenance plan approved in paragraph (c) of this section. New Hampshire will not conduct CO monitoring in Nashua, but instead commits to continue to collect and review CO monitoring data from nearby Manchester, NH on an on-going basis. In the event the second highest CO concentration in any calendar year monitored in Manchester reaches 75 percent of the federal 1-hour or 8-hour national ambient air quality standard for CO, New Hampshire will, within 9 months of recording such concentrations, re-establish a CO monitoring site in Nashua consistent with EPA siting criteria, and resume analyzing and reporting those data. New Hampshire commits to implement its contingency program in Nashua in the event that a CO violation is monitored at the re-established Nashua monitoring site at any time during the maintenance period. If the Manchester CO monitor measures a violation of the either the federal 1-hour or 8-hour NAAQS for CO, contingency measures will be implemented in Nashua as well, until a re-established CO monitor in Nashua shows that the area is in attainment of the CO standard.

(e) Approval - On August 1, 2012, the New Hampshire Department of Environmental Services submitted modifications to the Manchester and Nashua maintenance plans approved in paragraph (b) and (c) respectively of this section. The Manchester and Nashua current carbon monoxide maintenance plans are both converted to limited maintenance plans for the remainder of their second-ten year maintenance periods which terminate on January 29, 2021. 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. In addition, New Hampshire will no longer conduct CO monitoring in Manchester, New Hampshire as addressed in paragraph (d) of this section. The Manchester monitoring site is replaced with 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.