CA Gov't Code Section 31510.3

It is intended that disability benefits payable from the retirement system pursuant to Article 10 (commencing with Section 31720), in the event of the member’s termination of employment for disability, are compensation for personal injury or sickness, and therefore would not be subject to the limitations set forth in Section 415 of the Internal Revenue Code of 1986. If the Internal Revenue Service rules that the disability benefits are subject to those limitations, any employer which is subject to this article shall provide an alternate disability benefit equal to the decrease in the disability benefit caused by application of those limitations, through a long-term disability plan which shall be separate from the retirement system. The terms of that long-term disability plan shall be mutually agreed to by the employer and employee representatives and adopted by the board of supervisors.