### Question
How is the "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 follows -

> any area other than a high terrain area

#### Citation:
  - *42 U.S.C. § 7475*
  - Heading: **CHAPTER 85-AIR POLLUTION PREVENTION AND CONTROL > SUBCHAPTER I-PROGRAMS AND ACTIVITIES > Part C-Prevention of Significant Deterioration of Air Quality > subpart i-clean air**

