An active member of the General Assembly having no creditable service in the system, may establish creditable service for periods during which he or she was in an elective office and could have elected to participate in the system but did not so elect. Creditable service may be established by payment to the system of an amount equal to the contributions that would have been made if the person had elected to participate plus interest at the rate specified under subsection (a) of Section 16-128 to the date of payment, together with an equal amount as the applicable employer contributions, but the total period of such creditable service that may be validated shall not exceed 8 years.