Upon the happening of any emergency caused by fire, flood, explosion, storm, earthquake, epidemic, riot or insurrection, or caused by any inherent defect due to defective construction, or when the immediate preservation of order or of public health is necessary, or when the restoration of a condition of usefulness of any public building which has been destroyed by accident appears advisable or in order to settle lawful claims for personal injuries or property damage where such municipality is liable therefor under law, exclusive of claims arising from the operation of any public utility owned by the municipality, or in order to meet mandatory expenditures required by law, the board of governing authorities may, upon adoption by unanimous vote of all members present, at any meeting, of a resolution stating the facts constituting the emergency and entering the same upon its minutes, make the expenditures, borrow money, or incur the liabilities necessary to meet such emergency, without further notice or hearing, and may revise the budget accordingly.