86.250.  Members may retire when — application to board to be made when — compulsory retirement. — Retirement of a member on a service retirement allowance shall be made by the board of trustees as follows:

  (1)  Any member may terminate employment as a police officer and actually retire after completing twenty or more years of creditable service or attaining the age of fifty-five upon the member's written application to the board of trustees setting forth at what time, but not more than ninety days subsequent to the execution and filing of the application, the member desires to be retired;

  (2)  Any member in service who has attained the age of sixty-five shall be terminated as a police officer and actually retired forthwith provided that upon request of the chief of police the board of trustees may permit such member to remain in service for periods of not to exceed one year from the date of the last request from the chief of police.