Should any member of this plan retired for disability engage in a gainful occupation prior to attaining the age on which he or she would have been entitled to voluntary retirement for service, the retirement system manager shall reduce that part of the member's monthly retirement allowance which is provided by the contributions of the city so that the resultant retirement allowance (insofar as it still includes a portion provided by contributions of the city), when added to the amount earned monthly by the member in such occupation, will not exceed the greater of the following:
A. The amount of his or her final compensation; or
B. The amount of the compensation earnable by a person holding the position in the same salary step which he or she held at the time of his or her retirement, or if the position has been abolished, the maximum compensation earnable by the member holding it immediately prior to its abolition.
The reduction provided for in this section shall terminate when such member attains the age of eligibility for voluntary service retirement. (Prior code § 34.05.518)