The State Treasurer shall have custody of all moneys or funds paid or delivered to the authority and shall establish a separate account for each project of each local public body, and such moneys or funds shall be dedicated and used solely for the payment of any grant by the authority for the state to such local public body or, in case the bonds of the authority shall have been issued to fund such grant, the payment of the principal of and interest on such bonds, the expenses of such payment and any reserve fund required for such bonds by the authorizing resolution; provided, that if there shall be any surplus funds on deposit in said fund to the credit of the project of a local public body, then, upon application by such local public body, the State Treasurer may make cash expenditures from such account for any such project to the extent that moneys are available therefor in any fiscal year of the authority after there shall have been first set aside therein funds sufficient to provide the principal maturing and interest and reserve fund payments coming due in the ensuing fiscal year on the then outstanding bonds which have been issued to contribute to the cost of any prior project or projects of that particular local public body.