There was virtually no alternative to trenchless technology for the fibre optic expansion in the Polish Hanseatic city on the Oder in 2024: the successful implementation of three very long culverts was a prerequisite for connecting three parts of the city on the other side of the river to the distribution network. With the help of the Grundodrill 28Nplus from NODIG market leader TRACTO and the experience and expertise of the contractor Hydropex, these were completed in a remarkably short time.
With a population of just under 400,000, Szczecin is not only the seventh largest city in Poland, but also the largest city in the German- Polish conurbation, which is home to almost twice as many people. Located around 125 kilometres from Berlin, the city is not only an attractive university and educational location, but as a Hanseatic city it also has a large, well-connected Baltic Sea port. The cityscape is characterised by water, green spaces and numerous important historical and contemporary buildings. The densely populated city on the Oder is divided into different parts by several branches of the river, so that some parts of the city are located on river islands.
Against this backdrop, it becomes clear how challenging the project was for which Up-Telekom Sp. z.o.o. was responsible as general contractor: it involved the construction of a telecommunications distribution network in the form of a fibre optic trunk cable (Backbone that ran through the very densely built-up districts of Szczecin over a route length of 11,290 metres. In order to connect districts on the right bank of the Oder with the city centre, three inner-city arms of the river had to be crossed underneath, including the bank areas: The West Oder over a length of 231 metres, the Parnicki Canal over 210 metres and the Regalica River over a length of 426 metres.
HDD rig and crew master challenges
The highly experienced civil engineering company Hydropex, founded in 1989 and headed by Tomasz Raczynski, which has been using trenchless methods for seven years, was commissioned to realise the project. It was not only the long lengths of each undercrossing that posed a challenge for the company, but the geological conditions were also anything but uniform: in and around Szczecin there are often sandy and very sandy as well as clayey soils, some of which also contain peat, and there are also moraine soils in some areas.
The surroundings of the construction sites presented further challenges: The work always took place within densely built-up residential areas, in the immediate vicinity of the harbour infrastructure, in some cases while waterway shipping was in operation, in the vicinity of municipal roads, in shoreline areas and even under bodies of water, so that many imponderables had to be taken into account and at the same time interference with the surface and surroundings had to be kept to a minimum.
All three bores were done using the horizontal directional drilling method (HDD) with a GRUNDODRILL 28Nplus from TRACTO. HDD is an extremely flexible and efficient trenchless method that can be used for complex routes in a wide variety of soil conditions. In this process, at first the drilling rig's steerable bore head with rods attached creates a pilot bore along the planned bore path. A transmitter in the drill head continuously monitors drilling progress using a locating system, enabling corrections to be made if necessary. When the drill rod string is pulled back the bore channel is expanded by an upsizing head and the attached pipe is pulled in along the route. For the three river crossings in Szczecin, the pilot bores were largely located from a boat, which proved challenging in places due to depths of up to 19.2 metres and local signal interference. During the subsequent upsizing bores, HD-PE casing pipes with a diameter of 200 mm, that will later house the fibre optic trunk cables, were pulled in at the same time.
Crossing under the western Oder over 231 metres
During the 231-meter-long crossing of the West Oder River in the centre of Szczecin in July 2024, the Hydropex team monitored the pilot bore using a radio tracking system. Tracking was carried out over a distance of 100 meters from a motorboat. It was particularly challenging to work between the steel reinforcements of the quays, in the form of Larsen walls and horizontal anchors. At times, they had to penetrate an area 40 cm wide at a depth of 14 meters – which was anything but common given the signal interference caused by the steel. However, the team and the precisely steerable drilling rig mastered the task well, and the 210-meter-long pilot bore was completed within three work shifts.
210 metres long under the Parnicki Canal
During the pilot bore, which took place in September 2024, the drill head was tracked using an external cable-guided tracking system, which was supposed to be less sensitive to signal interference. However, the system did not prove to be so successful in practice, as the signal was repeatedly lost. After five-day shifts, the borehole was finally successfully expanded, and the pipeline was pulled in.
Record for Hydropex: 426 metres under the Regalica
The third culvert from this project was a record-breaking job for Hydropex: The 426-long culvert under the Regalica River is the longest undercrossing in the company's history to date, which had to be prepared at great expense due to the limited space available: the pipes were initially butt-welded and laid out oval due to the limited area.
This time, the pilot boring was again carried out using the company's own radio localisation system. In order to improve control and eliminate interference signals, shipping traffic was stopped for the duration of the test drilling and a 200-metre-long cable was stretched from shore to shore. These measures and the many years of experience of the employees ensured that this very long test drilling could be completed with great accuracy within just two working days. The Hydropex team was able to complete each individual undercrossing in an average of two weeks with a team of 6 to 9 employees.
HDD rig and bore crew master challenges
The contractor’s experience with the GRUNDODRILL 28N Plus was extremely positive: the 280 kN always ensured the appropriate output. The recording of all bore data was also extremely helpful, as it enabled the operators to gain a great deal of empirical values. For example, they were able to estimate the hardness of the formation by analysing previously completed sections.
The automation of the entire drilling process, from fully automatic rod handling to switching on the drilling fluid supply, significantly relieved the team of very physically demanding work and the operator was able to concentrate fully on the set parameters and adjust them during operation using potentiometers. The fuel consumption of just over 9 litres per hour was also found to be very economical for a 6-cylinder engine with an output of 300 hp. The machine's low noise emissions were also pleasing, ensuring that the driver can hear outside conversations and important information from inside the cabin.
Thanks to these features, the drill rig enabled Hydropex to successfully complete this project in challenging situational and geological conditions. Despite having only seven years' experience of working with the HDD method, the team learned a great deal from solving many unforeseen problems along the way. The company plans to invest in additional drilling rigs in the near future to enable it to take on larger projects.
It was clear to everyone involved that there was absolutely no alternative to the trenchless method for this project because open construction would have been extremely disruptive, costly and time-consuming, not only under the rivers and riverbanks, but also within the dense inner-city development. Using trenchless technology, the fibre optic network in Szczecin was expanded in a very short period of time in a minimally invasive, gentle and non-disruptive manner.
With a population of just under 400,000, Szczecin is not only the seventh largest city in Poland, but also the largest city in the German- Polish conurbation, which is home to almost twice as many people. Located around 125 kilometres from Berlin, the city is not only an attractive university and educational location, but as a Hanseatic city it also has a large, well-connected Baltic Sea port. The cityscape is characterised by water, green spaces and numerous important historical and contemporary buildings. The densely populated city on the Oder is divided into different parts by several branches of the river, so that some parts of the city are located on river islands.
Against this backdrop, it becomes clear how challenging the project was for which Up-Telekom Sp. z.o.o. was responsible as general contractor: it involved the construction of a telecommunications distribution network in the form of a fibre optic trunk cable (Backbone that ran through the very densely built-up districts of Szczecin over a route length of 11,290 metres. In order to connect districts on the right bank of the Oder with the city centre, three inner-city arms of the river had to be crossed underneath, including the bank areas: The West Oder over a length of 231 metres, the Parnicki Canal over 210 metres and the Regalica River over a length of 426 metres.
HDD rig and crew master challenges
The highly experienced civil engineering company Hydropex, founded in 1989 and headed by Tomasz Raczynski, which has been using trenchless methods for seven years, was commissioned to realise the project. It was not only the long lengths of each undercrossing that posed a challenge for the company, but the geological conditions were also anything but uniform: in and around Szczecin there are often sandy and very sandy as well as clayey soils, some of which also contain peat, and there are also moraine soils in some areas.
The surroundings of the construction sites presented further challenges: The work always took place within densely built-up residential areas, in the immediate vicinity of the harbour infrastructure, in some cases while waterway shipping was in operation, in the vicinity of municipal roads, in shoreline areas and even under bodies of water, so that many imponderables had to be taken into account and at the same time interference with the surface and surroundings had to be kept to a minimum.
All three bores were done using the horizontal directional drilling method (HDD) with a GRUNDODRILL 28Nplus from TRACTO. HDD is an extremely flexible and efficient trenchless method that can be used for complex routes in a wide variety of soil conditions. In this process, at first the drilling rig's steerable bore head with rods attached creates a pilot bore along the planned bore path. A transmitter in the drill head continuously monitors drilling progress using a locating system, enabling corrections to be made if necessary. When the drill rod string is pulled back the bore channel is expanded by an upsizing head and the attached pipe is pulled in along the route. For the three river crossings in Szczecin, the pilot bores were largely located from a boat, which proved challenging in places due to depths of up to 19.2 metres and local signal interference. During the subsequent upsizing bores, HD-PE casing pipes with a diameter of 200 mm, that will later house the fibre optic trunk cables, were pulled in at the same time.
Crossing under the western Oder over 231 metres
During the 231-meter-long crossing of the West Oder River in the centre of Szczecin in July 2024, the Hydropex team monitored the pilot bore using a radio tracking system. Tracking was carried out over a distance of 100 meters from a motorboat. It was particularly challenging to work between the steel reinforcements of the quays, in the form of Larsen walls and horizontal anchors. At times, they had to penetrate an area 40 cm wide at a depth of 14 meters – which was anything but common given the signal interference caused by the steel. However, the team and the precisely steerable drilling rig mastered the task well, and the 210-meter-long pilot bore was completed within three work shifts.
210 metres long under the Parnicki Canal
During the pilot bore, which took place in September 2024, the drill head was tracked using an external cable-guided tracking system, which was supposed to be less sensitive to signal interference. However, the system did not prove to be so successful in practice, as the signal was repeatedly lost. After five-day shifts, the borehole was finally successfully expanded, and the pipeline was pulled in.
Record for Hydropex: 426 metres under the Regalica
The third culvert from this project was a record-breaking job for Hydropex: The 426-long culvert under the Regalica River is the longest undercrossing in the company's history to date, which had to be prepared at great expense due to the limited space available: the pipes were initially butt-welded and laid out oval due to the limited area.
This time, the pilot boring was again carried out using the company's own radio localisation system. In order to improve control and eliminate interference signals, shipping traffic was stopped for the duration of the test drilling and a 200-metre-long cable was stretched from shore to shore. These measures and the many years of experience of the employees ensured that this very long test drilling could be completed with great accuracy within just two working days. The Hydropex team was able to complete each individual undercrossing in an average of two weeks with a team of 6 to 9 employees.
HDD rig and bore crew master challenges
The contractor’s experience with the GRUNDODRILL 28N Plus was extremely positive: the 280 kN always ensured the appropriate output. The recording of all bore data was also extremely helpful, as it enabled the operators to gain a great deal of empirical values. For example, they were able to estimate the hardness of the formation by analysing previously completed sections.
The automation of the entire drilling process, from fully automatic rod handling to switching on the drilling fluid supply, significantly relieved the team of very physically demanding work and the operator was able to concentrate fully on the set parameters and adjust them during operation using potentiometers. The fuel consumption of just over 9 litres per hour was also found to be very economical for a 6-cylinder engine with an output of 300 hp. The machine's low noise emissions were also pleasing, ensuring that the driver can hear outside conversations and important information from inside the cabin.
Thanks to these features, the drill rig enabled Hydropex to successfully complete this project in challenging situational and geological conditions. Despite having only seven years' experience of working with the HDD method, the team learned a great deal from solving many unforeseen problems along the way. The company plans to invest in additional drilling rigs in the near future to enable it to take on larger projects.
It was clear to everyone involved that there was absolutely no alternative to the trenchless method for this project because open construction would have been extremely disruptive, costly and time-consuming, not only under the rivers and riverbanks, but also within the dense inner-city development. Using trenchless technology, the fibre optic network in Szczecin was expanded in a very short period of time in a minimally invasive, gentle and non-disruptive manner.
