Challenging curved HDD in the middle of Florence

In the summer of 2022, Brownline surveyed a challenging HDD project in Italy. In the middle of Florence, contractor PATO S.r.l. installed a high voltage power cable using horizontal directional drilling. The pilot phase of this project was completed using Brownline’s Gyro Steering Tool.

The purpose of this installation was to replace overhead high voltage power lines and to install underground connections in their place. A busy intersection needed to be crossed to complete this project. Contractor PATO carried out this horizontal directional drilling, which had a challenging design.

The drill path curved 46° right before curving 72° left. The drilling was 406 m / 1332 ft long and crossed under an intersection with heavy traffic, a tramway, and the riverbed of the Mugnone.

Difficult soil conditions

The varied geological conditions posed another challenge to this HDD. The soil layers ranged from hard clay to gravel and stones. Brownline’s Drillguide Gyro Steering Tool was used to guarantee an accurate pilot hole, even with all these challenges facing this project. The GST is not affected by any interference from the surrounding infrastructure, so it is the perfect drilling solution for a project in such a busy urban area.

Using the highly accurate pitch & azimuth measurements from the GST, it was possible to follow the planned curve and reach the desired exit point. With this project, a safe underground connection was installed to replace the overhead power lines.

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