The face of the Emscher region is changing once again. It is more than a hundred years since a sparsely populated agricultural landscape was transformed into an industrial metropolitan area, and the naturally flowing Emscher became a manmade system of open sewers. With the decline of mining, a further structural change has set in, with the traditional heavy industry making way for high technology and the service sector. The end of mining subsidence now also makes it possible in our region to drain wastewater in closed underground sewers, and step by step to transform the river and its subsidiary waterways into near-natural bodies of water – an intergenerational project.
The Emscher Conversion not only offers the chance of a century to give a new face to the urban landscape between Holzwickede and Dinslaken. The aim is to decisively enhance the value of the Emscher region through projects that extend far beyond the waterway, sustainably changing the living and working environment of the population. The planning basis for this is the Emscher Future masterplan, published in 2006. Many of the ideas it drafted out have today become reality, the Emscher Present. This can be experienced in many places, e.g. along the converted Emscher and at Phoenix Lake in Dortmund, in the Berne Park in Bottrop and at the Emscher Experience in the Oberhausen Kaisergarten. Through its updates, the masterplan will now contribute to bringing together the experience of the water management sector and the latest requirements for the development of a future-proof Emscher region.
The main artery of the new drainage system is the Emscher wastewater sewer running between the Dortmund-Deusen wastewater treatment plant and the Emschermündung wastewater treatment plant in the city triangle of Dinslaken, Oberhausen and Duisburg. Along a length of 51 kilometres this wastewater sewer will take up the wastewater of more than 1.8 million inhabitants and large wastewater volumes from industry and trade and route them to the Bottrop wastewater treatment plant and the Emschermündung wastewater treatment plant. The wastewater is routed to the main sewer via subterranean sewers which are built at the same time in parallel to the tributaries of the Emscher.
For the Emscher wastewater sewer a route has been selected that is orientated along the old drainage system and therefore along today’s course of the Emscher river. Similar to above-ground routes, detailed planning was required here. Obstructions, contaminated sites or off-limits areas – for example built-up surface areas, geologically critical spaces or the Rhine-Herne Canal – had to be identified and circumnavigated when the route was specified.
At the initial shaft in Dortmund the sewer has a depth position of approx. eight metres below ground. In a continuous descent of 1.50 metres per kilometre it then bores itself into the ground down to a depth of up to 40 metres. It was thus unavoidable to integrate pumping stations which convey the wastewater upwards again. Without these the sewer would have reached a depth of 75 metres at Dinslaken!
The extreme depth position of the Emscher wastewater sewer is technically demanding but offers many advantages. Thus, for example, installations such as roads and railway lines or the Rhine-Herne Canal and its locks can be underrun; in addition, the jacking work takes place in homogeneous building ground. The depth position also permits connection of the side canals from the Emscher subsidiary catchment areas in a free descent.
The Emscher wastewater sewer was designed as an armoured concrete sewer. The future wastewater will stress the sewer to a high degree so that clear answers had to be found as early as the planning phase for material questions, questions of corrosion, aeration and ventilation as well as for health and safety issues. For the Emscher wastewater sewer a minimum utilisation period of 100 years was established.
With regard to the system and operating reliability of the Emscher wastewater sewer designed as a mono-pipe sewer, Emschergenossenschaft has come up with a special solution. If a section of the sewer failed, the wastewater would be passed on by means of pumps and of temporarily installed pressure pipelines. The limits for this solution are a delivery rate of 3 m³/s and a depth position of 25 metres. Where these limits need to be exceeded, even today the Emscher wastewater sewer is already built as a dual pipe sewer.