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State Implementation Plans

NHDES’ approach to attaining and maintaining federal air quality standards.

blue sky and clouds behind the Old Man in the MountainWhen the EPA establishes or revises a National Ambient Air Quality Standards (NAAQS), it sets in motion a series of actions to ensure that air quality throughout the country meets those standards. Within two years after setting a new or revised NAAQS, EPA must designate areas as meeting (attainment) or not meeting (nonattainment) the standard. Within three years after setting the NAAQS, all states must submit a state implementation plan, known as an infrastructure SIP, to show they have the basic air quality management program components in place to implement a new or revised NAAQS. If an area has been designated as nonattainment for the standard, the state has 18-36 months after designations, depending on the pollutant and area classification, to submit nonattainment area SIPs. Each nonattainment area SIP must outline the strategies and emissions control measures that show how the area will improve air quality in order to meet the NAAQS. In addition, the Clean Air Act mandates that areas adopt certain specified control requirements. These plans are developed by NHDES with public input and submitted to EPA for approval. State plans also must control emissions that drift across state lines and harm air quality in downwind states and in addition, since NH is included in the Ozone Transport Region, New Hampshire must submit SIPs for the pollutants that form ozone regardless of attainment status. Specified controls (e.g., Reasonably Available Control Technology (RACT) for existing sources, and Lowest Achievable Emission Rate (LAER) and offsets for new sources) are required in the OTR.

SIPs are the mechanism by which states set emission limits and allocate pollution control responsibility among sources to meet the limits on ambient concentrations of criteria pollutants. This is accomplished through a process that involves collecting emission inventory, monitoring ambient pollutant concentrations, modeling emissions to determine reductions needed to attain the NAAQS and imposing appropriate emission limits on new and existing industrial sources.

Typically, the three parts of a SIP include:

  1. State-adopted control measures which consists of either air pollution control regulations or source-specific requirements that are more applicable to the situation than the corresponding state rule.
  2. Clean Air Act (CAA) required elements that demonstrate that New Hampshire has the ability to adequately implement the SIP to EPA’s satisfaction (such as attainment plans, rate of progress plans, emission inventories, transportation control measures, statutes demonstrating legal authority, monitoring networks, adequate staffing, etc.).
  3. Additional requirements to address national issues.

Once a nonattainment area has air quality meeting the NAAQS, the state can request that the area be redesignated to attainment. Several conditions must be met. For example, EPA must determine that the improvement in air quality is due to permanent and enforceable emissions reductions. EPA must have approved the state’s maintenance plan, which must provide for maintaining clean air in the area for at least 10 years after the redesignation. Also, the state must have met all applicable implementation plan requirements for the area.

trees impacted by acid rainNew Hampshire’s Acid Rain Program

Acid rain is more correctly referred to as acid deposition because in addition to rain, acid can deposit as snow, sleet, hail, particles, gasses and water vapor. NOx and SO2 gas emissions from manmade and natural sources react in the atmosphere to form nitric and sulfuric acids. Winds can carry these pollutants hundreds of miles from the emissions sources where they are deposited to the earth. Acid rain damages aquatic life and ecosystems, acidifies forest soils, damages property, and forms from pollution that degrades visibility and harms public health. In 1985, the state Legislature established New Hampshire’s Acid Rain Control Act, which authorized NHDES to develop an acid deposition control program which was codified in Env-A 400, Acid Deposition Control Program. Nationally, EPA has made extensive progress to address air pollutants from the power sector through its various regulatory programs such as the Acid Rain Program, Cross-State Air Pollution Rule (CSAPR) and the Mercury and Air Toxics Standards.

Acid Rain Impacting Ecosystems  

plume of smoke from a smokestackFederal Standards and State Plans for New and Existing Sources

Section 111 of the CAA established a mechanism for controlling air pollution from categories of industrial sources such as power plants, incinerators, and municipal solid waste landfills. These federal regulations include minimizing pollution from new or expanded sources (New Source Performance Standards) as well as pollution from existing sources covered by emission guidelines. NH is a delegated state for many of the NSPS, meaning that NHDES incorporates the NSPS requirements in permits and enforces many of the provisions contained in the federal regulations. States use the federal emission guidelines to develop state plans for existing sources that are at least as stringent as the federal requirements. NH has developed a state plan for municipal waste combustors (MWC) and other solid waste incinerators (OSWI). NHDES has been delegated the federal plan for sewage sludge incinerators and plans to take the federal plan for municipal solid waste (MSW) landfills. 

State Plans for Existing NH Sources  

side-by-side comparison of clear and hazy skyRegional Haze refers to periods when manmade air pollutants impair visibility. Particles and some gasses block or reflect light, obscuring views of distant objects. The federal regional haze rule aims to reduce manmade air pollutants to improve visibility at over 150 national parks and wilderness areas with the goal of achieving natural conditions by 2064. In New Hampshire, this includes the Great Gulf Wilderness and the Presidential Dry River Wilderness, both of which surround Mt. Washington. New Hampshire is currently in the process of drafting the state’s SIP for the second implementation period (2018-2028) as well as the progress report for the first implementation period (2008-2018).

More information about Regional Haze 

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Did You Know?

Did You Know?

New Hampshire is part of the Ozone Transport Region (OTR). Therefore, NHDES must submit SIPs for the pollutants that form ozone regardless of the attainment status of the state for those pollutants. This includes nitrogen oxides (NOx) and volatile organic compounds (VOCs).

SIP Development Section
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Chief Scientist
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