EPA releases draft guidance to re-define “ambient air.”

December 22, 2018

EPA is considering a redefinition of “ambient air” according to a November 2018 E&E News report. Currently defined by EPA as “that portion of the atmosphere, to which the general public has access,” ambient air’s definition exempts outdoor areas over land that’s owned or controlled by a pollution source, to which “public access is precluded by a fence or other physical barriers,” under an interpretation dating back to 1980.

But in a November 2018 released draft guidance document titled “Revised Policy on Exclusions from “Ambient Air”, EPA cites stakeholders who argue that this interpretation is overly restrictive for purposes of carrying out air quality analyses needed when applying for Prevention of Significant Deterioration permits under the Clean Air Act’s New Source Review program.

The broader interpretation laid out in EPA’s memo says public access may be deterred by other barriers, including drones, security patrols and “rugged terrain.”

Accordingly, EPA wants to replace “a fence or other physical barriers” with a more expansive rendering: “measures, which may include physical barriers, that are effective in deterring or precluding access to the land by the general public.”

While the guidance doesn’t include an analysis of the potential impact, EPA predicts the proposed change will furnish more flexibility in deciding the location of modeling receptors used in air quality analyses while “maintaining public health protection.”

EPA will accept public comment on the draft guidance through January 11, 2019. Although the revised guidance doesn’t qualify as a regulation requiring advance public notice, EPA expects state and local air agencies to adopt the policy when issuing Prevention of Significant Deterioration permits, according to the memo.
Under the New Source Review program, those pre-construction permits are needed when a power plant or other major industrial facility embarks on a significant expansion or upgrade expected to lead to more pollution in areas that currently meet national ambient air quality standards.

What this means to you
EPA is considering a more expansive redefinition of “Ambient Air” which is now currently defined as “that portion of the atmosphere to which the general public has access.” The current definition exempts outdoor areas over land that’s owned or controlled by a pollution source, to which public access is precluded by a fence or other physical barriers. EPA wants to replace “a fence or other physical barriers” with more expansive wording: “measures, which may include physical barriers, that are effective in deterring or precluding access to the land by the general public.

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