Brian McCarthy Gayle Hartmann Alma Williams Roberta Delaney v. Lee M. Thomas City of Tucson

Opinion by Judge WIGGINS.

WIGGINS, Circuit Judge:

Plaintiffs below (“Appellants”) sought from the district court an order requiring the cities of Tucson and Phoenix to enlarge their mass transit systems. Specifically, Appellants asserted that Tucson and Phoenix must comply with certain mass transit proposals that Arizona submitted to the EPA in the late 1970s and early 1980s. The district court disagreed with Appellants and entered summary judgment for the cities. We reverse.

I

A. Statutory Framework

As amended in 1970, the Clean Air Act (“CAA”) required the EPA to establish national ambient air…