Burying sewerage under pavements in an era of sealed and heavily trafficked roadways is both extremely inconvenient for repairs and extremely expensive. A major portion of the cost of an underground sewerage system is not for transporting faecal matter but rather for supporting the weight and impact of heavy trucks that bear upon the system. It is little wonder that both the installation of new systems and the maintenance of old systems seems now beyond the financial resources of many municipalities.
One rational reason for burying sewerage systems underground, at least in the colder winter climates of the northern hemisphere, is to avoid having vast quantities of frozen sewage. Another has to with the professional competencies of the engineer, which in most countries inextricably combines the design skills for building roads, drainage and sewerage networks, usually within a narrow band of public land called a services ccorridor or easement.