South Feeder Cologne

There are not enough natural watercourses available to drain the catchment areas to the west of Cologne. As a result, in the past, the responsible local authorities had the southern lateral duct and the Cologne lateral duct constructed as artificial feeders to the River Rhine. As it became evident that these additional feeders would no longer be able to cope with the sewage from new residential and industrial zones in the south of Cologne and from neighbouring communities, the city of Cologne together with Hürth and Frechen, which belong to the "Zweckverband Südlicher Randkanal" decided to build a further feeder using mining means. The altogether 10.5 km long structure was split up into 3 construction lots depending on the different pipe cross-sections with lot 4 consisting of the Rhine outlet plant Lots 3 and 4 embrace 2,885 m of tunnel section DN 3600, 12 inspection shafts, a cut-off valve as well as the outlet plant. The client's draft foresaw the building of a tunnel by pipe jacking in 7 straight sections including the 7 starting and target shafts required. A special proposal by the joint venture, which called for reducing the number of jacking sections from 7 to 5, something which meant that 2 target shafts would not be needed. In this way, the traffic at the nearby motorway distributor link was not affected. A further advantage of the special proposal was a central construction site installation at the biggest available area at shaft s 26. As a result, lot 3 was divided into 2 sections, which were driven one after the other. It was necessary to relocate the complete tunnelling equipment on several occasions. The shield only had to be placed on a cradle in shafts S/Z 27, S/Z 29 and S/Z 24. Only the shaft installation had to be relocated. The elimination of the 2 target shafts S/Z 25 and S/Z 28 resulted in an extension of the jacking sections up to a maximum length of 940 m as well as the driving of 2 curves with a radius of 450 m.

• Country: Germany
• Region: Nordrhein-Westfalen
• Tunnel utilization: Utilities
• Type of utilization: Sewage
• Client: Zweckverband Südlicher Randkanal-Städte Köln, Hürth, Frechen
• Consulting Engineer: Obermeyer Planen + Beraten, Michael Müller
• Contractor: Philipp Holzmann AG, Dyckerhoff & Widmann AG
• Main construction method: Trenchless
• Type of excavation: Pipe jacking
• No. of tubes: 1
• Tunnel total length: 2,835 m
• Cross-section: 3.60 m (DM), 16.6 m² (QS)
• Contract Volume: 46 mill. DM
• Construction start/end: 18 months
• Opening: March 1998