(a) The proceeds from the sale of any bonds issued under authority of this article may be applied only for the purpose for which the bonds were issued: Provided, That any accrued interest received in any sale shall be applied to the payment of the principal of or the interest on the bonds sold. If for any reason any portion of the proceeds are not needed for the purpose for which the bonds were issued, then the unneeded portion of the proceeds shall be applied to the purchase of bonds for cancellation or payment of the principal of or the interest on the bonds or held in reserve for the payment thereof.
(b) The costs of any public project shall be considered to include the following:
(1) Capital costs, including, but not limited to, the actual costs of the construction of public works or improvements, capital improvements and facilities, new buildings, structures and fixtures, the demolition, alteration, remodeling, repair or reconstruction of existing buildings, structures and fixtures, the removal or containment of, or the restoration of soil or groundwater affected by environmental pollution, environmental remediation, the acquisition of equipment and site clearing, grading and preparation;