EPA floats redefinition of ‘ambient air’

By Sean Reilly | 11/09/2018 04:14 PM EST

In another bid to speed approval of industry permits, EPA is re-airing its regulatory definition of “ambient air.”

EPA headquarters in Washington.

EPA headquarters in Washington. Claudine Hellmuth/E&E News

In another bid to speed approval of industry permits, EPA is re-airing its regulatory definition of "ambient air."

Currently defined as "that portion of the atmosphere, to which the general public has access," ambient air 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But in newly released draft guidance, EPA cites unspecified stakeholders who argue that this interpretation is overly restrictive for purposes of carrying out air quality analyses needed when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 the unsigned 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."

Abstract as the proposed change might sound, it was welcomed today as a practical improvement by the head of the American Forest and Paper Association.

"By clarifying where the public is truly exposed, EPA eliminates many hypothetical modeling scenarios that can bog down projects unnecessarily," Donna Harman, the association’s president and CEO, said in a statement.

Harman said past assessments have been done for areas where the public doesn’t have legal access. "This action," she said, "takes a long-overdue first step toward ensuring real-world air quality modeling is used to determine any air quality impacts from a project."

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."

With no public announcement, the agency posted the draft guidance online late this week. Spokesman John Konkus didn’t reply to a request for confirmation of the exact day.

The agency is asking "interested stakeholders" to furnish comments by Dec. 21. 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.