### Question
How is the term high terrain area” means with respect to any facility, any area having an elevation of 900 feet or more above the base of the stack of such facility, and the term “low terrain area defined?


### Answer
The term **high terrain area” means with respect to any facility, any area having an elevation of 900 feet or more above the base of the stack of such facility, and the term “low terrain area** is defined in *42 U.S.C. § 7475* as the following:

> any area other than a high terrain area

#### Citation:
  - *42 U.S.C. § 7475*
  - Heading: **SUBCHAPTER I-PROGRAMS AND ACTIVITIES > Subchapter Referred to in Other Sections > Part C-Prevention of Significant Deterioration of Air Quality > &sect;7470**

