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Regional Haze

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What is Regional Haze?

Good visibility is essential to the enjoyment of national parks and scenic areas. “Regional haze” is air pollution that is transported long distances and reduces the visibility in these areas. Across the country, regional haze has decreased visibility from 140 miles to 35-90 miles in the West, and from 90 miles to 15-25 miles in the East. This haze is composed of small particles that absorb and scatter light, affecting the clarity and color of what we see. Sources of this haze are both urban and rural, such as motor vehicles, power plants, industrial and manufacturing processes, and outdoor debris burning, as well as natural sources such as wildfire and windblown dust. Regional haze is a national problem, affecting visibility in national parks and wilderness areas across the country.

The federal Clean Air Act contains requirements for states to protect and improve visibility in national parks and wilderness areas in the country. In 1977 Congress designated certain national parks and wilderness areas as “Class I areas”, where visibility was identified as an important value. Currently in the United States there are 156 Class I areas. Oregon has 12 Class I areas, including Crater Lake National Park and 11 wilderness areas. These areas are important not only in the intrinsic value of their beauty but also in their importance to tourism in Oregon. They are also valuable as a recreational resource for Oregon residents.

To address the problem of regional haze, the Environmental Protection Agency (EPA) adopted the Regional Haze Rule in 1999. This rule is intended to improve visibility in all Class I areas, including Oregon, over the next 60 years. It focuses on improving Class I area visibility on the haziest days (the worst 20%) and ensuring no degradation on the clearest days (the best 20%). For the first time, states will be required to work together to improve visibility through interstate planning and implementation of regional strategies. States must revise their State Implementation Plans (SIP) as part of this process.

Presentation: Regional Haze in Oregon

Oregon's Regional Haze Plan

On June 19, 2009 the Environmental Quality Commission adopted a regional haze plan for Oregon. On December 9, 2010, the Commission adopted revisions to the plan that would close the PGE Boardman coal-fired power plant by 2020.

DEQ regulation of PGE Boardman

Other Haze and Visibility Programs



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Oregon Department of Environmental Quality
Headquarters: 700 NE Multnomah Street, Suite 600, Portland, OR 97232
Phone: 503-229-5696 or toll free in Oregon 1-800-452-4011
Oregon Telecommunications Relay Service: 1-800-735-2900  FAX: 503-229-6124

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the State of Oregon and the Environmental Protection Agency.

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