CA Gov't Code Section 27206

The county recorder may destroy federal tax liens together with any release of said liens eight years after the lien was filed in his office; provided, a microfilm copy of each unreleased tax lien has been made and certified in the manner provided for in Section 1551 of the Evidence Code. All film used in the microphotography process shall comply with the minimum standards of quality approved by the United States Bureau of Standards. The original copy of the microfilm shall be kept in a safe and separate place for security purposes.