political subdivisions. That is, economic forces within the market would be the key to including or excluding a specific property. The service district for a parking facility is generally limited to the geographic area from which pedestrians would walk between businesses and the parking structure. An example might be that users of a parking structure will traverse an area defined as being within six blocks or less of a parking structure. In this example, the service district would consist of all properties lying within six blocks of the parking structure. However, there may be more than just retail business structures within the six block area. All classes of properties lying within the distance shoppers can reasonably be expected to walk to and from retail outlets could include a block of homes or an industrial facility. The commercial properties would be assessed because surveys would illustrate that retail sales depend upon adequate parking for customers. It could also be demonstrated that residential properties (homes), would be excluded because users of those properties might not reasonably be expected to "benefit" from the parking structure. Depending upon various scenarios, industrial properties might similarly, not "benefit", from a parking structure. Benefit There are variations between state governments as to what constitutes a “benefit” under special assessment laws. In general, the "benefit" must result directly, uniquely and specifically from the public project. For example, when water and sewer lines are installed by government units, nearby land often increases in value. Both the presence of safe drinking water and of sewer lines means that expensive wells and septic systems do not have to be installed by affected property owners. It also means the potential for contamination of ground water and surface areas from improperly treated sewage will be eliminated. Land that might have been “unbuildable” before may become "buildable" once government provided water and sewer services become available. Providing water and sewer service are situations which may adapt formerly unusable land for residential or commercial use. A storm sewer or a dam or dike may mitigate flooding and therefore the sewer, dike or dam relieves a burden, flooding. The term benefit most frequently means an increase in the market value of the benefited property. However, some states historically have defined the term benefit to mean more than an increase in market value. For example, benefit may mean a special adaptability of the land or a relief