Section 9.4  REFUND
   The excess by which any special assessment proves larger than the actual cost of the improvement and expenses incidental thereto shall be refunded on a pro rata basis to the owners of the property assessed.  This refund shall be made by credit against unpaid future installments to the extent that installments are still owing, and the balance of the refund shall be in cash.  No refunds may be made which contravene the provisions of any outstanding evidence of indebtedness secured in whole or in part by the special assessment.  Minimum refund shall be of five dollars ($5.00).