65 ILCS 5/11-70-3

All money received from this public building restoration fund tax shall be deposited in the municipal treasury to the credit of that fund. All money so received shall be kept separate and apart from other money of the municipality, and shall not be used or paid out for any other purpose than that of paying the cost of rebuilding or restoring the specified public buildings destroyed or seriously impaired by storm or fire, until all of the costs have been discharged. If the money so received can not be used annually to pay the cost but accumulates, the corporate authorities may invest this money in good interest-paying securities, until the money is needed for the payment of the costs of the rebuilding or restoration.