The proceeds of such bonds shall be used solely for the payment of the cost of the project for which they are issued and shall be disbursed by the Board under such restrictions, if any, as the Board may provide. If the proceeds of the bonds of any issue, by error of estimates or otherwise, shall be less than the cost of the project on account of which such bonds are issued, additional bonds may in like manner be issued to provide the amount of such deficit and unless otherwise provided in the resolution authorizing the issuance of the bonds or in the trust indenture pursuant to § 33.2-1717 shall be deemed to be of the same issue and shall be entitled to payment from the same fund without preference or priority of the bonds first issued for the same project. If the proceeds of bonds issued for any project exceeds the cost thereof, the surplus shall be paid into the fund provided in this chapter for the payment of principal and interest of such bonds.