Rural residential sprawl usually occurs away from existing central sewer and water. Homeowners rely on on-site septic systems and on wells for water. Often, these systems are not properly sited or not properly maintained. For example, a 1998 study in the Indiana reported that between 25 and 70 percent of the on-site septic systems in the state were failing. When septic systems fail in large numbers, sewer and water lines must be extended into the countryside, often a mile or more.
Public sewer is priced according to average cost pricing.
This means that when sewer lines are extended, there is a strong incentive to encourage additional hook-ups along the line. So when a sewer line is extended a mile or more, development pressure increases along the line. This usually results in a sprawling pattern, like a hub and spoke from a village to the countryside. This puts greater demands on existing roads and increases the demand for more and better roads. The greater traffic also results in the burning of more fossil fuels, producing more air pollution.