Specifications include, but are not limited to: The Chicago Department of Aviation (CDA) is seeking a Contractor to provide all labor, materials, supplies, tools and equipment for the new installation, repair, or replacement of noise abatement fences (Services) at Chicago Midway International Airport. The Contractor must provide the services in response to normally scheduled requests by CDA as well as on an emergency basis. Time is of the essence in this Contract and the Contractor agrees that the work must be started within a minimum of four (4) hours after notification in the case of an emergency, or as directed by the Commissioner of Aviation. The Commissioner will make the sole determination as to what constitutes an emergency.