40 C.F.R. § 81.134
The Austin-Waco Intrastate Air Quality Control Region (Texas) consists of the territorial area encompassed by the boundaries of the following jurisdictions or described area (including the territorial area of all municipalities (as defined in section 302(f) of the Clean Air Act, 42 U.S.C. 1857h(f) ) geographically located within the outermost boundaries of the area so delimited):
In the State of Texas: Bastrop County, Bell County, Blanco County, Bosque County, Brazos County, Burleson County, Burnet County, Caldwell County, Coryell County, Falls County, Fayette County, Freestone County, Grimes County, Hamilton County, Hays County, Hill County, Lampasas County, Lee County, Leon County, Limestone County, Llano County, Madison County, McLennan County, Milam County, Mills County, Robertson County, San Saba County, Travis County, Washington County, Williamson County.
40 C.F.R. §81.134