Replacement sewerage Hoorn 

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Customer challenge
In 2012, the municipality of Hoorn decided to replace the DWA and HWA sewers throughout Molenwijk. In the new sewer design, the choice was made to construct the central DWA drain in the district access road De Weel. In part of De Weel, the sewer had to be laid at a great depth (maximum 4.00 below ground level). In addition, the only access road was not to be blocked.

What was our solution
In the existing asphalt, sections of 3 * 3 meters have been sawn in which immersion wells are placed. The immersion wells were supplied and provided with a cutting edge after which the internal excavation started. By excavating the internal well, the well sank by itself after which it was extended so that the correct depth was reached. The PBA 85 drill has been used to carry out various drillings of up to approx. 60 metres in length from the wells using vitrified clay DN 300 drill pipes. For these drillings a pilot drilling with optical navigation system was first carried out, which enabled the required accuracy to be guaranteed. After the pilot drilling, the drill head with water lock was mounted with which the vitrified clay drill pipes were attached. The wells were then further finished so that they can be used as sewer wells.

What were the advantages of this
The combination of concrete immersion wells and pilot-controlled auger drilling, especially in busy (residential) areas, is very well applicable. The low level of inconvenience to traffic, local and surrounding businesses, as well as the reduction of risks, make this a very suitable implementation method. This project won the NSTT No-Dig Award in 2014. The NSTT No-Dig Award is presented annually for a project, concept or research that contributes to the further development of trenchless techniques.