(a) Approval - On November 13, 1992, the Massachusetts Department of Environmental Protection submitted a revision to the carbon monoxide State Implementation Plan for the 1990 base year emission inventory. The inventory was submitted by the State of Massachusetts to satisfy Federal requirements under section 182(a)(1) of the Clean Air Act as amended in 1990, as a revision to the carbon monoxide State Implementation Plan.

(b) Approval - On December 12, 1994, the Massachusetts Department of Environmental Protection submitted a request to redesignate the Boston Area 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 (1993 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 a subsequent maintenance plan revision in 8 years 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), Massachusetts will implement one or more appropriate contingency measure(s) which are contained in the contingency plan. The menu of contingency measures includes an enhanced motor vehicle inspection and maintenance program and implementation of the oxygenated fuels program. 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. The redesignation meets the Federal requirements of section 182(a)(1) of the Clean Air Act as a revision to the Massachusetts Carbon Monoxide State Implementation Plan for the above mentioned area.

(c) Approval - On May 25, 2001, the Massachusetts Department of Environmental Protection submitted a revision to the carbon monoxide State Implementation Plan for the 1996 base year emission inventory. The inventory was submitted by the State of Massachusetts to satisfy Federal requirements under section 172(c) of the Clean Air Act as amended in 1990, as a revision to the carbon monoxide State Implementation Plan.

(d) Approval - On May 25, 2001, the Massachusetts Department of Environmental Protection (MADEP) submitted a request to redesignate the cities of Lowell, Springfield, Waltham, and Worcester from 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 1996 emission inventory for carbon monoxide, a demonstration of maintenance of the carbon monoxide NAAQS with projected emission inventories to the year 2012 for carbon monoxide, a plan to verify continued attainment, a contingency plan, and an obligation to submit a subsequent maintenance plan revision in 8 years as required by the Clean Air Act. If an area records an exceedance or violation of the carbon monoxide NAAQS (which must be confirmed by the MADEP), Massachusetts will implement one or more appropriate contingency measure(s) which are contained in the contingency plan. 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.

(e) Approval - On April 14, 2010, the Massachusetts Department of Environmental Protection submitted a modification to the Lowell maintenance plan approved in paragraph (c) of this section. Massachusetts will not conduct CO monitoring in Lowell, but instead commits to continue to collect and review CO monitoring data from nearby Worcester, MA on an on-going basis. In the event the second highest CO concentration in any calendar year monitored in Worcester reaches 75 percent of the federal 1-hour or 8-hour national ambient air quality standard for CO, Massachusetts will, within 9 months of recording such concentrations, re-establish a CO monitoring site in Lowell consistent with EPA citing criteria, and resume analyzing and reporting those data. Massachusetts commits to implement its contingency program in Lowell in the event that a CO violation is monitored at the re-established Lowell monitoring site at any time during the maintenance period. If the Worcester CO monitor measures a violation of either the federal 1-hour or 8-hour NAAQS for CO, contingency measures will be implemented in Lowell as well, until a re-established CO monitor in Lowell shows that the area is in attainment of the CO standard.