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This website includes a summary of the air quality analysis and conformity determination process for Fine Particulate Matter (PM2.5) and provides the public an opportunity to comment on PM2.5 analyses for selected projects. PM2.5 is particulate matter that is 2.5 microns or less in diameter.

Particulate matter (PM) refers to particles and liquid droplets suspended in the air. PM2.5 (fine particulate matter) refers to particles that are 2.5 micrometers in diameter or less. Motor vehicles emit direct PM from their tailpipes and from normal brake and tire wear. Vehicles cause dust from paved and unpaved roads to be re-suspended in the atmosphere; highway and transit project construction may cause dust, and vehicle exhaust gases may react in the atmosphere to form PM.

On March 10, 2006, the Environmental Protection Agency (EPA) published a final rule (71 CRF 12468) that established requirements for transportation conformity and developed procedures to determine which transportation projects must be analyzed for local air quality impacts in PM2.5 and PM 10 non-attainment and maintenance areas. Non-attainment areas are locations in violation of PM 2.5 standards. There are no PM 10 non-attainment areas in Maryland. Maintenance areas are locations that were once in violation of PM 2.5 standards that currently produce lower levels of PM 2.5. These maintenance areas are monitored by the Maryland Department of the Environment (MDE) and must have an approved Clean Air Act section 175A maintenance plan (71 FR 12468).

If you require more information you can contact EPA at their websites

When is a PM2.5 Analysis Required?

In general, this determination is made by considering whether the project is:

  1. Within a PM2.5 nonattainment or maintenance area;
  2. Exempt from review under 40 CFR 93.126 (Table 2- Exempt Projects) or 40 CFR 93.128 (Traffic Signal Synchronization Projects);
  3. Not a project of air quality concern per 40 CFR 93.123(b)(1), or
  4. A project of air quality concern per 40 CFR 93.123(b)(1)

The MD SHA Interagency Consultation and Public Involvement Process

Projects Not of Air Quality Concern

After review, the Federal Highway Administration (FHWA) will provide SHA with comments on the documentation resulting from the air quality analysis. Once all FHWA comments are addressed, the project’s PM 2.5 documentation will be forwarded for Interagency Consultation in conformance with 40 CFR 93.105. The Interagency Consultation Group (ICG) includes a representative from FHWA, EPA, MDE, and the appropriate Metropolitan Planning Organization (MPO). If the ICG has questions or concerns, SHA will address those issues and resubmit the documentation to FHWA where it will be reviewed and passed back to the ICG. For projects not of air quality concern for which the NEPA process has not been completed, the standard NEPA public involvement process will be used to fulfill the PM 2.5 interagency consultation review requirement. Projects requiring an Environmental Assessment (EA) or Environmental Impact Statement (EIS) will have a formal public hearing. For projects not of air quality concern that have already completed the NEPA process but require other approvals (design, right-of-way, construction), a notification including the documentation and project-level PM 2.5 conformity determination will be published on SHA’s project website for a period of 15 days.

Projects of Air Quality Concern

Projects determined to be of air quality concern will require a PM 2.5 project-level hot-spot analysis. The interagency review process for an analysis performed for projects of air quality concern will be similar to the process discussed above for projects not of air quality concern but will have an extended review period of 30 days. For projects of air quality concern that have already completed the NEPA process but require other approvals (design, right-of-way, construction), the results of the analysis and project-level PM2.5 conformity determination will be posted on SHA’s website or the project website for a period of 15 days. On a case-by-case basis, a notification of the PM 2.5 air quality analysis and its results may also be placed in local papers.

Click Here for projects which currently have a PM2.5 Air Quality Analysis posted for public review & comment