Subpart R Rule
Subpart R, National Emission Standards for Radon Emissions from Phosphogypsum Stacks, limits radon emissions from phosphogypsum stacks and requires disposal of phosphogypsum in stacks or piles, with exceptions for agricultural and research uses and other uses on a case-by-case basis.
The requirements of Subpart R apply to the following groups:
- phosphogypsum stack owners
- phosphoric acid producers
- agricultural users
- entrepreneurs who wish to use phosphogypsum in their research products
Subpart R was first issued in 1989 and has subsequently been modified in response to petitions from the regulated groups for clarifications or modifications. The most recent modification was finalized in February1999.