Employees who become members of the Vermont State Retirement System under the provisions of this subchapter shall contribute at the same rate and in the same manner as if they were employees of the State of Vermont. The actuary of the System shall compute the contributions which would be payable annually by the employer on behalf of such members corresponding to the contributions which the State of Vermont makes on behalf of State employees, except that each employer of members participating in the Vermont State Retirement System as provided in this subchapter shall make a special accrued liability contribution on account of the participation of its employees, which shall be determined by an actuarial valuation of the accrued liability on account of the employees of such employer who become members, in the same way as the accrued liability rate was originally determined for employees of the State of Vermont. This special accrued liability contribution, subject to such adjustment as may be necessary on account of any additional credits for service prior to the date of participation of its employees in the System awarded by such employer, shall be payable in lieu of the accrued liability contribution payable on account of other employees in the Vermont State Retirement System. The expense of making the valuation to determine any special accrued liability contribution shall be assessed against and paid by the employer on whose account it was necessary. Prior to the determination of the special accrued liability contribution the employer shall make accrued liability contributions at the accrued liability rate payable by the State of Vermont on behalf of State employees. (Added 1971, No. 231 (Adj. Sess.), § 4.)