In the summer of 2019, Brownline returned to the 2nd Maasvlakte Port to work on the expansion of the wind farm “Hollandse Kust Noord”. The cable installation for this project will take place in 2020 and 2021 and required the installation of 4 PE-HD 800mm ducts under the Maasvlakte’s sea defense in 2019.
For our client, a major German company, The Gyro Steering Tool’s characteristics were ideal for this challenging project. The Maasvlakte port consists of a dense network of busily used roads and waterways, which makes it difficult to lay out cables onshore. Due to the tidal effects and the dense shipping traffic the installation of guidance cables offshore was virtually impossible. The punch out point for each drill was located offshore, in a pre-dredged pit. The pilot drills were executed as sack holes without exiting onto the seabed. This meant that precise and trustworthy positioning while drilling were extremely important, since the actual exit position could not be verified until after the reamer had done its job. At this stage, a correction of the position would have been impossible. We are proud to say that at each of the 4 drills, the reamer broke the sea bed exactly at the predetermined point.
The reason for executing the pilot drills without exiting at the sea bed punch out is that it enabled reaming of the borehole from the rig towards the sea while maintaining full returns of the drilling fluid to the entry point. The advantage of working this way is that no bentonite was spilled in to the sea, while at the same time the required amounts of fresh water and bentonite were reduced.
With the drill site’s location being at the edge of the very busy shipping lane to Europe’s largest port transportation and handling of the ducts offshore was restricted by the port authorities. Because of this, the 18 meter long sections of which each ducts consist, were welded together and tested on shore. After the pre-reaming was completed, the ducts were entered pushed into the borehole from on shore to off shore using a pipe pusher. This special technique requires excellent preparation and planning.
During construction, we encountered the additional challenge of various ground water levels. This situation caused pressure in the bore holes after reaming. Special measures were necessary and implemented to handle this situation. All 4 ducts were installed successfully and exactly as planned.