It is estimated that the public sewer system in Germany has a total length of more than 400,000 kilometres. Many say 500,000 kilometres. The drains of private property do not even begin to be included in this enormous length. They are estimated at around another 1.5 million kilometres. Nobody knows exactly how this underground labyrinth is constructed. Rats probably know it best of all. The authorities are trying to record the overall condition of the network, especially of public reaches, in sewer registers and databases. Damage to the network identified here is unfortunately not the exception but rather the rule. As far as the undetected damage goes, we can only speculate. In Germany, legislation requiring local authorities to check their own sewers has significantly stimulated demand for repair work. The legislation calls for the condition of all sewers and pipelines, including private ones, to be recorded (and repaired) by 2015. A mammoth project. And everywhere people now know that there is a great deal to do.
Environmental Protection and Cost Efficiency
Out of sight, out of mind?
The cost and impact when damage adds up
When we talk of leaks, we always think of effluent seeping out. But what about liquids seeping in? The infiltration of external water into the sewers interferes with the smooth operation of water treatment plants. The impact of outward leaks (exfiltration) is, however, also often talked down. There are experts who talk about the soil’s filtering effect. Or about its self-purifying effect. More recent findings in this area are, however, less encouraging. It is also being rash to pin our hopes on biodegradability. There are some situations where degradation actually causes toxicity to increase. In Singapore they have begun to make the pipeline network watertight in order to keep the costs of processing purified drinking water from contaminated ground water in check. Sewers that are not watertight lead to the formation of cavities. Entire streets or railway lines can cave in as a result of undercutting. And, of course, an intact sewer network cannot be had for nothing. It’s a balancing act between conserving resources, technical feasibility and financial affordability. However, the desire for an intact environment is becoming ever stronger.