StacksVerified U.S. regulatory reference

40 CFR §61.204

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Phosphogypsum may be lawfully removed from a stack and distributed in commerce for use in outdoor agricultural research and development and agricultural field use if each of the following requirements is satisfied:
  1. (a)The owner or operator of the stack from which the phosphogypsum is removed shall determine annually the average radium-226 concentration at the location in the stack from which the phosphogypsum will be removed, as provided by § 61.207.
  2. (b)The average radium-226 concentration at the location in the stack from which the phosphogypsum will be removed, as determined pursuant to § 61.207, shall not exceed 10 pCi/g (4500 pCi/lb).
  3. (c)All phosphogypsum distributed in commerce for use pursuant to this section by the owner or operator of a phosphogypsum stack shall be accompanied by a certification document which conforms to the requirements of § 61.208(a).
  4. (d)Each distributor, retailer, or reseller who distributes phosphogypsum for use pursuant to this section shall prepare certification documents which conform to the requirements of § 61.208(b).
  5. (e)Use of phosphogypsum for indoor research and development in a laboratory must comply with § 61.205.