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Air Resources

Assessment, Monitoring and Expertise

In managing air resources, the BLM Air Program conducts NEPA analyses for air resources that draw on air quality assessments and air quality monitoring. The BLM also cultivates in-house technical expertise throughout the Air Resource Management Program, offers training, and shares expertise with project proponents and other stakeholders.

NEPA Analysis of Potential Impacts to Air Resources

Prior to authorizing an activity or action on BLM administered public lands (such as by issuing a Resource Management Plan or authorizing a lease sale for oil and gas development), the BLM must analyze the proposed action’s potential impacts on air resources through the NEPA process. For example, the BLM evaluates the potential impacts of energy and mineral resource development, recreational uses, smoke management, transportation management, and other activities on air resources.

Key aspects of the BLM’s NEPA review with respect to air resources include:

Analyzing potential impacts on air quality

  • National Ambient Air Quality Standards
  • State Ambient Air Quality Standards

Analyzing potential impacts on air quality related values (AQRVs)

  • Visibility
  • Nitrogen and Sulfur Deposition
  • Lake Acidification

Analyzing potential impacts on greenhouse gas (GHG) emissions

Evaluating and recommending appropriate best management practices (BMPs) or other measures to mitigate adverse impacts on air resources and ensure compliance with appropriate standards, coordinating with regulatory agencies

Ensuring that authorizations such as leases or permits include appropriate stipulations or conditions of approval to manage air resources

Air Resources Assessment Tools

In analyzing the potential impacts of BLM and BLM-authorized activities on air resources under NEPA, the BLM uses tools that include emissions inventories and air quality modeling. The BLM also uses air quality monitoring data to assess the impacts of BLM and BLM-authorized activities on air resources and to understand long-term trends in air quality on a regional scale.

Emissions Inventories

Emissions inventories are listings of emission sources and their emissions in a given land use plan or project, geographic area, or organization. Emissions inventories are based on measurements, if available, as well as “emission factors” and methods for estimating emissions from existing sources where measurements are not available and from new sources that have not yet been built. These emission factors and estimation methodologies are provided in guidelines developed by the EPA. There are different types of emissions inventories used for different purposes.

Land use plan- or project-specific emissions inventories include only the emission sources associated with a planning area or project development. These inventories are used in NEPA analyses to consider potential impacts to air resources and determine whether further air quality analysis (including modeling) is appropriate. For example, project-level inventories for natural gas development typically include only local sources such as diesel powered compressors, drill rig engines and vehicle traffic on dirt and gravel roads.

Multi-state or regional inventories include the emissions from of all types of sources over large areas. Regulatory agencies use these comprehensive inventories to assess the relative contribution of each source type to issues such as regional haze or photochemical smog. These inventories include all sources, including power plants and refineries, residential and commercial furnaces and boilers, vehicle traffic on public roads, agricultural and landscaping equipment, airplanes, vessels, and locomotives. EPA prepares these inventories when developing national rules under the Clean Air Act, and state regulatory agencies use them when preparing State Implementation Plans (SIPs) to bring air quality in their jurisdictions into compliance with the National Ambient Air Quality Standards (NAAQS).

In addition, the BLM works with the U.S. Department of the Interior (DOI) to compile an annual greenhouse gas (GHG) emissions inventory and report under Executive Order 13514, “Federal Leadership in Environmental, Energy, and Economic Performance,” which tracks the GHG emissions within the BLM’s organizational and operational boundaries and provides information to assist the DOI in reducing its GHG emissions by fiscal year 2020. The October 2009 Executive Order aims “to establish an integrated strategy toward sustainability in the Federal Government and to make reduction of greenhouse gas emissions a priority for Federal agencies,” which will lead by example. Follow these links to learn more about the Federal government’s first ever GHG inventory: GHG inventory for all Federal Agencies and GHG inventory for the Department of the Interior

For NEPA analyses, the BLM air resource specialists can assist in determining when it is appropriate to prepare an emissions inventory and what that inventory should include for a specific planning or project action.

Air Quality Modeling

Dispersion models use mathematical and numerical techniques to simulate the physical and chemical processes that affect air pollutants as they disperse and react in the atmosphere. Based on inputs of meteorological data and source information like emission rates and stack height, these models are used to estimate the potential air quality impacts of new sources or to evaluate the effectiveness of control strategies. There are different types of dispersion models used for different purposes.

Simple screening techniques make conservative assumptions to determine whether a single source has the potential to cause adverse air quality impacts. Refined dispersion models use more realistic assumptions and local meteorological and terrain data to assess compliance with air quality standards and potential impacts on visibility and other AQRVs. Highly complex photochemical models simulate chemically reactive pollutant transport from multiple sources over large spatial scales.

The Appendix to the Memorandum of Understanding contains two tables recommending general air quality modeling approaches for oil and gas development under various conditions (e.g., planning phase, data quantity/quality, and potential air quality impacts). It includes a matrix summarizing characteristics of currently available air quality models, applicability, and references.

As part of the MOU, the BLM and other agencies have developed a reusable modeling framework for the development of air quality modeling products that can be used at the various stages in National Environmental Policy Act (NEPA) documents. While not prescriptive, the framework is intended to promote the development of air quality modeling analysis in a manner that reduces overall resource expenditures through reuse of data, modeling systems, or results.

EPA’s Support Center for Regulatory Atmospheric Modeling (SCRAM) provides the models themselves and additional guidance for applying air quality models for regulatory applications.

Air Quality Monitoring

The BLM collaborates with federal, state, and private partners to monitor the overall air quality within airsheds where activities such as oil and gas development are occurring or anticipated. Such ambient monitoring focuses on compliance with the National Ambient Air Quality Standards (NAAQS) and the “criteria pollutants” regulated by the NAAQS, such as ground-level ozone.

In recent years, the BLM has recognized the importance of increasing air quality monitoring on public lands, particularly near areas with high potential for energy development. The BLM maintains or supports some fixed monitoring network stations and has begun to use portable ozone monitoring stations to gather additional data.

The BLM developed an Air Resource Management Monitoring Strategy in 2006 “to provide direction and support to all Bureau Programs and Offices regarding the design, collection, quality, analysis, and data management of air resource-related information needed to address its legislative and regulatory requirements for managing the Public Lands.” The Strategy identifies the basis for monitoring, alternative methods of “monitoring,” basic monitoring components, and a summary of key considerations when planning, conducting, archiving, and distributing monitoring information.

Currently, the BLM is cooperating with the Federal Leadership Forum (EPA Region 8, OAQPS, NPS, USFS, and BLM) and three States (Colorado, Utah, and Wyoming) to develop and operate a regional air quality data warehouse. The data warehouse will support future air quality modeling for NEPA analyses, as well as the recent national MOU between EPA, DOI, and USDA, which establishes a common process that five participating agencies including the BLM will use for examining the air quality effects of oil and gas development on Federal lands.

The BLM also engages in other collaborative air quality monitoring efforts. For example, the BLM:

Funds and operates six National Atmospheric Deposition Program (NADP) monitoring stations in Alaska (one), Colorado (two), and Wyoming (three)

Funds and operates eight monitoring stations in Wyoming as part of the Wyoming Air Resources Monitoring System (WARMS)

Funds and operates interagency Remote Automatic Weather Stations (RAWS) to monitor the weather and provide weather data that assists land management agencies monitor air quality, rate fire danger, and provide information for research applications

Serves as a member of the steering committee for the Interagency Monitoring of Protected Visual Environments (IMPROVE) program that monitors visibility and aerosol conditions in pristine areas

Air monitoring data can be found at several web locations. The Visibility Information Exchange Web System (VIEWS) is an online decision support system developed to help western states, tribes, federal land managers (FLMs), scientists, planners, and students evaluate air quality and visibility in federally-protected ecosystems. The Clean Air Status and Trends Network (CASTNET) is the primary source for data on dry acidic deposition and rural, ground-level ozone. Real-time air monitoring data can be found at EPA’s AIRNow website. Historical data can be found on EPA”s AirData website. Individual state agencies also prepare annual air monitoring reports, which can be found on each state’s air program web site.

Technical Expertise and Training

The BLM is cultivating technical expertise across the Air Program and among managers and staff BLM-wide, collaborating with the National Training Center (NTC) and Federal, state, tribal, and local partners and stakeholders. Check out the following training resources developed for the BLM:

The National Training Center’s August 10, 2011, “M Street Live!” satellite broadcast on the new NEPA Air Quality MOU among USDA, DOI, and EPA to address air quality issues associated with oil and gas development on Federal lands.

An Introductory Soil, Water and Air training course that is being developed by a team of BLM Air Resource Specialists, the BLM Training Coordinator for Soil, Water, Air, and Climate, and Instruction Specialists at the NTC. Once completed, the course will be offered by webinar and will be available through DOI Learn, which can be accessed through the NTC’s website.

General training resources related to air resources can be found at:

EPA’s Air Pollution Training Institute website, offering a variety of self-instructional training materials and in-person classes on technical topics.

The Smoke Management and Air Quality for Land Managers tutorial provides information on the air quality impacts of fires, relevant air quality regulations, smoke management techniques, and collaborative smoke management approaches.


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