No documentation or particular methods required. I think that https://www.hhs.gov/sites/default/files/disposalfaqs.pdf is equivalent to the guidance at the time, and it just requires ‘reasonable safeguards’.

> For PHI on electronic media, clearing (using software or hardware products to overwrite media with non-sensitive data), purging (degaussing or exposing the media to a strong magnetic field in order to disrupt the recorded magnetic domains), or destroying the media (disintegration, pulverization, melting, incinerating, or shredding).