Required setbacks of buildings or structures and other physical features. No building or structure shall be located within 100 feet of a property line. All portions of the property within 75 feet of a property line shall remain open and unused, as a buffer from adjoining properties, except that within such buffer area only the following physical features may be located, with the approval of the Board of Trustees: fences, driveways, sidewalks, landscaping, shrubbery and plantings.