For the purpose of these regulations, the following terms have the meanings indicated: “Excess property” means any real property under the control or jurisdiction of a State agency which the head of that agency determines is not required for the current or projected needs or the discharge of the responsibilities of that agency. “Real property” means any freehold, fee, or leasehold interest in land, including improvements of any kind, structures and fixtures located on the premises, and appurtenances. “State agency” means a department or independent agency of State government. “Substantial change” means any change in use that would: Result in a major alteration in the functions or services being provided through or by the facility concerned; Require physical alteration to a structure or structures whose estimated cost of alteration is $50,000 or more; Require the demolition or removal of a usable structure whose estimated value is $15,000 or more. “Surplus property” means any real property which the Board of Public Works determines is not required for current or projected needs or the discharge of responsibilities of the State or its political subdivisions, and which will be disposed of under certain conditions as the Board may require.