Additional member contributions or deposits to annuity savings fund

In addition to the contribution deducted from compensation as hereinbefore provided, subject to the approval of the board of trustees any member may redeposit in the annuity savings fund a single payment or by an increased rate of contribution an amount computed to be sufficient to purchase an additional annuity, which together with his prospective retirement allowance, will provide for him a total retirement allowance of not to exceed one-half of his average final compensation at age sixty. Such additional amounts so deposited shall become a part of his accumulated contributions except in the case of retirement, when they shall be treated as excess contributions returnable to the member in cash or as an annuity of equivalent actuarial value and shall not be considered in computing his pension. The accumulated contributions of a member withdrawn by him, or paid to his estate or to his designated beneficiary in the event of his death as provided in the Chapter, shall be paid from the annuity savings fund. Upon the retirement of a member his accumulated contributions shall be transferred from the annuity savings fund to the annuity reserve fund.