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June 26, 2016
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Home > Transportation > Planning Activities > Air Quality > Clean Air Act Amendments

The Clean Air Act Amendments

The Washington metropolitan region's most serious air pollution problem is ozone. Ozone exists naturally in the earth's upper atmosphere, the stratosphere, where it shields the earth from the sun's ultraviolet rays. However, ozone found close to the earth's surface, called ground-level ozone, is considered an air pollutant. Ozone is a harmful gas that is formed when volatile organic compounds (VOCs) and nitrogen oxides (NOx) react with sunlight.

The 1990 Clean Air Act Amendments (CAAA) require the Washington region and about 100 other areas with air quality problems to take a structured, multi-year approach to attaining federal clean air standards within federally established deadlines. The deadlines vary according to the severity of the region's air pollution problems.

The CAAA links transportation planning and clean air planning in several ways. Most critically, federal highway funding aid may be withheld as one of the sanctions imposed for failure to meet CAAA requirements. Secondly, the region must show that its transportation plans and programs are in conformity with the region's clean air plans. Finally, the region's clean air plans include transportation emission reduction measures (TERMs) intended to reduce emissions from mobile sources, which are given a special, priority status for federal-aid funding in the region's annual Transportation Improvement Program (TIP).

The CAAA and the Washington Region

The CAAA set a 1999 deadline for Washington to solve its ozone problem. Phase I elements of a regionally coordinated plan for achieving clean air by 1999 were developed between 1993 and 1997 by the Metropolitan Washington Air Quality Committee (MWAQC) for submission to the U.S. Environmental Projection Agency (EPA) by the states of Maryland and Virginia, and the District of Columbia in their State Implementation Plans (SIPs). These regionally coordinated SIP submissions are also referred to as:

  • the Fifteen Percent Plan that showed how the region planned to reduce VOC emissions 15% by 1996 (from 1990 baseline emission levels), and
  • the Nine Percent Plan, that showed how the region planned to reduce VOC and NOx emissions by 9% between 1996 and 1999.

MWAQC also developed and approved a Phase II Attainment Plan, which addressed attainment of the health standards by 1999. The plan included local controls on VOC and NOx and also relied on the reduced transport of ozone and its precursors from outside areas into the Washington region to attain the health standards. This Phase II Attainment Plan, which demonstrated attainment but for ozone transport, was completed and submitted to EPA in April 1998. An updated Phase II Attainment Plan, focusing on attainment of the ozone standards by 2005, was approved by MWAQC in March 2000 and subsequently was approved by EPA in January 2001.

In July 2002 a court decision remanded EPA's approval of the region's Phase II Attainment Plan to EPA for reconsideration. As a result, in the November 13, 2002 Federal Register EPA published a proposed rule which would reclassify the region to a "severe non-attainment area." when the proposed action is finalized, the region will be obliged to meet a number of additional requirements, including development of a new 2005 attainment plan and emissions budgets. MWAQC and TPB policy bodies and staff are currently working together to prepare the 2005 Severe Area Attainment Plan.

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