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Regional Haze

Overview

In 1977, Congress amended the Clean Air Act establishing a national goal to protect visibility in Class I federal areas — national parks, forests and wilderness areas. The amendments called for the “prevention of any future, and the remedying of any existing, impairment of visibility in mandatory Class I federal areas which impairment results from manmade air pollution.” In 1979, EPA promulgated a list of 156 mandatory Class I areas in which visibility was determined to be an important factor. In Nevada, there is one designated Class I area, the Jarbidge Wilderness Area in the northeast corner of the State.

Class I Wilderness Areas in and near Nevada
Class I Wilderness Areas in and near Nevada
Mary River's Peak in the Jarbidge Wilderness Area during a fire event
Mary River's Peak in the Jarbidge Wilderness Area during a fire event
Mary River's Peak in the Jarbidge Wilderness Area during a haze event
Mary River's Peak in the Jarbidge Wilderness Area during a haze event
Mary River's Peak in the Jarbidge Wilderness Area during a clear day in the summer season
Mary River's Peak in the Jarbidge Wilderness Area during a clear day in the summer season

On July 1, 1999, EPA promulgated the Regional Haze Rule. The intent of the regional haze rule is to improve visibility over a period of 60 years in all 156 mandatory Class I areas across the country. It requires each affected state to develop and adopt a state implementation plan (SIP) that will improve the haziest days and protect the clearest days at each mandatory Class I area in the state with a goal of returning to natural visibility conditions by the year 2064. Comprehensive SIP revisions are required every 10 years and must provide a comprehensive analysis of natural and man-made sources of haze in each mandatory Class I area in the state and contain strategies to control anthropogenic emissions that contribute to haze. The plan must also address the transport of haze across state boundaries.

Most of the technical work for the initial regional haze SIPs in the western states was done through the Western States Air Resource Council and the Western Regional Air Partnership (WESTAR/WRAP). WESTAR/WRAP is a collaborative effort of tribal governments, state governments and various federal agencies to develop the technical and policy tools needed by western states and tribes to comply with EPA's regional haze regulations. WESTAR/WRAP activities are conducted by a network of committees and forums composed of WESTAR/WRAP members and stakeholders, representing a wide range of viewpoints. More information and educational materials on regional haze are found on EPA's Visibility website, which includes basic information on visibility science and Class I area maps, as well as links to regulations.

Nevada’s 2022 Regional Haze State Implementation Plan

NDEP submitted the 2022 Regional Haze SIP on August 12, 2022, addressing the second planning period of the Regional Haze Rule, 2018-2028. The 2022 Regional Haze SIP demonstrates that Nevada is continuing to achieve reasonable progress in reducing haze in the Jarbidge Wilderness Area and in Class I areas in neighboring states that may be impacted by emissions from Nevada.

NDEP calculated the baseline, current, and natural visibility conditions record at Jarbidge WA during both the most impaired days and clearest days. During the most impaired days, visibility conditions at Jarbidge WA have shown a steady improvement in visibility since the baseline conditions were calculated during the initial implementation period and confirms that visibility conditions at Jarbidge WA are on track to achieve natural conditions by 2064. During the clearest days, NDEP has confirmed that current visibility conditions have not degraded since the previous round. Data collected since the 2014 progress report suggests that visibility at Jarbidge WA is significantly impacted by both anthropogenic and natural sources.

Nevada’s 2025 Regional Haze State Implementation Plan Revision

Changes to the energy landscape along with transmission system reliability considerations in Nevada necessitated reconsideration of portions of the 2022 Regional Haze SIP. On July 13, 2023, NV Energy notified NDEP of plans to file an Integrated Resource Plan amendment with the Public Utilities Commission of Nevada seeking approval to pursue modifications and appropriate emissions controls at the Tracy and North Valmy Generating Stations. Since the Tracy and North Valmy Generating Stations were part of Nevada’s 2022 Regional Haze SIP, NDEP submitted a letter on July 27, 2023, informing the USEPA of its partial withdrawal of the Nevada 2022 Regional Haze SIP.  A four-factor re-analysis of the North Valmy Generating Station and Tracy Unit 4 Piñon Pine was completed, and new reasonable progress requirements were established for the second planning period. NDEP submitted the revision to replace the withdrawn elements in the 2022 Regional Haze SIP on May 27, 2025. The Regional Haze SIP Revision also incorporates by reference updated permits for the Lhoist Apex and Graymont Pilot Peak facilities.

Nevada’s 2025 Regional Haze Progress Report

Nevada’s 2025 Regional Haze Progress Report assesses progress midway through the second planning period of the Regional Haze Rule. The Progress Report found that many of the emission reductions required for reasonable progress have not yet been achieved since implementation of additional control measures are dependent on approval of Nevada’s 2022 RH SIP. While emissions reductions from regional haze SIP strategies have not yet been realized, emissions in the state of Nevada have decreased during the second planning period as reported by the National Emissions Inventory and Clean Air Markets Program Data. Visibility at Jarbidge WA has experienced a slight decline since the second planning period but has seen an overall net improvement in visibility since the 2000-2004 baseline for both the most impaired and clearest days. This slight decline is likely associated with increases in wildfire and windblown dust events as evidenced by annual extinction compositions. After the consideration of visibility trends, emission data, and the expectation of additional emissions reductions from control measures, NDEP has determined that Nevada’s 2022 RH SIP with the 2024 RH SIP Revision is adequate to achieve the 2028 reasonable progress goals and no further revision is necessary.

Regional Haze Documents for the Second Planning Period

Nevada 2022 Regional Haze SIP

    Nevada 2025 Regional Haze SIP Revision

    Nevada 2025 Regional Haze 5-Year Progress Report

    Federal Register Notices

    Nevada's 2009 Regional Haze SIP

    The Nevada Division of Environmental Protection (NDEP) submitted the first Nevada Regional Haze State Implementation Plan on November 18, 2009, addressing the initial planning period of the Regional Haze Rule, 2008-2018. The 2009 Regional Haze SIP demonstrates reasonable progress in reducing haze in the Jarbidge Wilderness Area and in Class I areas in neighboring states that may be impacted by emissions from Nevada. Analyses conducted for the SIP show that visibility impairment at the Jarbidge Wilderness Area is primarily due to natural emissions of smoke and dust from wildfire and windblown dust. 

    A key component of the first planning period of the Regional Haze Rule is the requirement to install and operate the best available retrofit technology (BART) for qualifying older, existing sources of visibility impairing pollutants during the initial planning period. Implementation of BART and other Clean Air Act components of the 2009 plan reduced 2018 anthropogenic emissions from Nevada sources by tens of thousands of tons annually, including industrial, transportation and urban emissions, resulting in visibility improvements in the Jarbidge Wilderness Area and other Class I Areas.

    Nevada's 2014 Progress Report

    The Nevada Regional Haze 5-Year Progress Report assesses progress midway through the initial planning period of the Regional Haze Rule. Submitted on November 18, 2014, it assesses visibility improvements since 2004 and documents that Nevada’s initial SIP is adequate to achieve established goals for visibility improvement and emissions reductions by 2018. The report concludes that Nevada’s 2009 SIP requires no substantive revision at this time.

    Regional Haze Documents for the First Planning Period

    Nevada 2009 Regional Haze State Implementation Plan (SIP)

    Nevada 2014 Regional Haze 5-Year Progress Report

    NDEP'S BART Determination Reports

    Federal Register Notices

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