In March and April 2025, Brownline surveyed two HDD crossings in Denmark. On the island of Falster, work is underway on expanding the power grid. Thanks to precise measurement techniques, the cables could be installed with trenchless methods, deep under two straits.
The horizontal directional drills were carried out by contractor Jacob Post Styret Underboring A/S. To guide the crossings with the highest accuracy under the straits, they were surveyed with the Drillguide Gyro Steering Tool.
Sortsø: 1000 meters, 90% under water
At Sortsø, the strait between Falster and Bogø was crossed with an HDD of almost 1000 m (3300 ft). No less than 90% of the trajectory was under water, at a depth of about 60 meters.
Guldborgsund: 700 meters, 80% under water
Further southeast, the Guldborgsund was crossed, the strait between Falster and Lolland. Here, a 700 m (2300 ft) crossing was made, 80% of which was under water.
Accurate navigation was crucial in both jobs. The drills needed to pass under the strait at the correct depth and without deviations to arrive correctly at the planned exit point. The Drillguide Gyro Steering Tool was chosen, as it is the most accurate steering tool in the world. This made it possible to rely on highly precise measurements.
Both drills reached the other side of the water at the desired point without any issues. This allowed the power cables to be installed with minimal disturbance and maximum efficiency.