Environmental aspects and future-oriented thinking lead the municipality of Groningen in the Netherlands to extending their existing sewer main sized DN 1000 and DN 1200. The gravity sewer main could not cope with high flow rates occurring during heavy rainfall. To prevent sewage from overflowing and polluting nature the authorities decided to convert it into a closed pressure system. With this and its extension by 2.4 km HOBAS CC-GRP Sewer Systems a capacity of 3000 m³/h will be achieved so that the line would easily cope with future needs as well as the connection of a further village.
The three other microtunneling sections were implemented with in this field unique CC-GRP pressure jacking pipes PN 6 and flush FWC couplings. These run beneath a gas pipeline, a main road, several streets and a navigable channel where the installation was conducted in 12 m depth. A 275 m long section with CC-GRP pressure jacking pipes of 1280 mm outer diameter was jacked in a curve radius of 1300 m. The contractor decided to install an intermediate station which according to safety standards is required for jacking with over 4000 kN. Due to the smooth and non-absorbing outer surface of HOBAS Pipes their light weight and constant outer diameter, the maximal jacking force did not exceed 1800 kN. The intermediate station was therefore never in operation.
December 2008
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