Public Comment Period Open for Ozone and Fine Particulates PSD SILs

Clean Air Act Redesignation for Houston Ozone Nonattainment Area
June 27, 2016
Recommended Designations for 2015 Ozone NAAQS Nonattainment Areas
August 23, 2016

Waid Environmental News
The EPA has opened a period for public comment on proposed SIL values for Ozone and Fine Particulates (PM2.5, particulate matter with an aerodynamic diameter at or below 2.5 microns) for the federal Prevention of Significant Deterioration (PSD) program. The PSD program, authorized by the Clean Air Act, and detailed in the Code of Federal Regulations (CFR), Title 40, Part 51, Subpart I, is used to ensure that newly proposed and/or modified facilities may not cause a significant deterioration to local, regional, or national air quality. The significant impact level (SIL) values are used during an impacts analysis at the facility site to determine whether the proposed new and/or modified facilities will lead to a significant impact in the surrounding areas. In simpler terms, a SIL value represents the threshold for air quality impacts away from the facility between insignificant (safe) and significant (potentially unsafe). If the SIL is not surpassed by the impacts test, it can be reasonably stated that the proposed construction project will not cause harm to the surrounding environment or human health. If the SIL is surpassed, then a more intensive impacts analysis must be conducted to ensure the proposed construction project, in addition to all pre-existing sources nearby, will not cause harm.

The comment period for the newly proposed SIL values for Ozone and PM2.5 closes after September 30, 2016. To submit a comment, find the draft guidance documentation, and all other information regarding this proposal, please visit