28 CFR 22.25: Final disposition of identifiable materials.
Upon completion of a research or statistical project the security of identifiable research or statistical information shall be protected by:
(a) Complete physical destruction of all copies of the materials or the identifiable portion of such materials after a three-year required recipient retention period or as soon as authorized by law, or
(b) Removal of identifiers from data and separate maintenance of a name-code index in a secure location.
The Privacy Certificate shall indicate the procedures to be followed and shall, in the case of paragraph (b) of this section, describe procedures to secure the name index.