Major Source

Major Source in the United States

Major Source in Environmental Law

Under the 1970 Clean Air Act, a pollution source is considered a major source if it is stationary and has the potential to emit 100 tons per year or more of a regulated air pollutant. The Clean Air Act Amendments of 1990 made the definition more inclusive by lowering the threshold of 100 tons per year for certain facilities: those that emit hazardous air pollutants or those located in an air district that has not attained the national air quality standards for the pollutant they discharge. See hazardous air pollutants; National Ambient Air Quality Standards; National Emission Standards for Hazardous Air Pollutants; nonattainment areas.

A stationary source may consist of more than one building. For purposes of determining the status of the facility, the government aggregates all facilities managed by the same person if they are near each other. The pollutant tonnage considered is not what the source actually emits but what it is capable of emitting. This figure is based on facility design: how much pollution would the source generate if it were operating at peak capacity? In some situations, if the source owner or manager agrees to limit plant operations so that it does not exceed certain levels, and if those levels are enforceable by the government, the Environmental Protection Agency (EPA) may consider actual emissions instead of potential emissions when deciding whether or not the source is major. Several courts have also determined that if the source is modifying its facility, the EPA should consider past operating practices to calculate future emissions.

Hazardous air pollutant dischargers are considered major sources if they have the potential to emit 10 tons per year or more of one hazardous air pollutant or 25 tons per year of any combination of hazardous air pollutants. In nonattainment areas for any of the criteria pollutants (ozone, nitrogen oxides, sulfur dioxide, lead, and small particulates), a source may be considered major at a level as low as 10 tons per year if it discharges the pollutant the area is having trouble with.

Once a facility is designated a major source, a permitting requirement for operation as well as other restrictions are triggered. All of the pollutants it emits will be regulated. For example, if a plant discharges 100 tons per year of nitrogen oxides but is below that amount for sulfur dioxide, it is still a major source. When the permit is written, it will include limits for sulfur dioxide as well as nitrogen oxides. A new major source or existing major facility that wants to modify its plant or operation is also required to go through preconstruction review and permitting before it can begin construction. Minor sources are not regulated to the same degree.
Based on “Environment and the Law. A Dictionary”.

Major Source: Open and Free Legal Research of US Law

Federal Primary Materials

The U.S. federal government system consists of executive, legislative, and judicial branches, each of which creates information that can be the subject of legal research about Major Source. This part provides references, in relation to Major Source, to the legislative process, the federal judiciary, and the primary sources of federal law (cases, statutes, and regulations).

Federal primary materials about Major Source by content types:

Laws and Regulations

US Constitution
Federal Statutory Codes and Legislation

Federal Case Law and Court Materials

U.S. Courts of Appeals
United States courts of appeals, inclouding bankruptcy courts and bankcruptcy appellate panels:

Federal Administrative Materials and Resources

Presidential Materials

Materials that emanate from the President’s lawmaking function include executive orders for officers in departments and agencies and proclamations for announcing ceremonial or commemorative policies. Presidential materials available include:

Executive Materials

Federal Legislative History Materials

Legislative history traces the legislative process of a particular bill (about Major Source and other subjects) for the main purpose of determining the legislators’ intent behind the enactment of a law to explain or clarify ambiguities in the language or the perceived meaning of that law (about Major Source or other topics), or locating the current status of a bill and monitoring its progress.

State Administrative Materials and Resources

State regulations are rules and procedures promulgated by state agencies (which may apply to Major Source and other topics); they are a binding source of law. In addition to promulgating regulations, state administrative boards and agencies often have judicial or quasi-judicial authority and may issue administrative decisions affecting Major Source. Finding these decisions can be challenging. In many cases, researchers about Major Source should check state agency web sites for their regulations, decisions, forms, and other information of interest.

State rules and regulations are found in codes of regulations and administrative codes (official compilation of all rules and regulations, organized by subject matter). Search here:

State opinions of the Attorney General (official written advisory opinions on issues of state law related to Major Source when formerly requested by a designated government officer):

Tools and Forms

Law in Other Regions

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