Projects involving participating Federal-aid funds may be undertaken by the Department of Natural Resources after it has been determined that sufficient funds are available to the Department for meeting the non-federal share of project costs. It is the legislative intent that, to such extent as may be necessary to assure the proper operation, maintenance and preservation of historic properties and interests surveyed, acquired or developed pursuant to any program participated in by this State under authority of this Act, such historic properties and interests shall be publicly maintained for historic preservation purposes. The Department of Natural Resources may enter into and administer agreements with the United States or any appropriate agency thereof for survey, planning, acquisition, development and preservation projects involving participating Federal-aid funds on behalf of any county, city, other governmental unit or qualified participant provided such county, city, other local governmental unit or qualified participant gives necessary assurances to the Department of Natural Resources that it has available sufficient funds to meet its share of the cost of the project and that the surveyed, acquired or developed historic properties and interests will be operated and maintained at its expense for historic preservation purposes.