New water pipeline laid using the horizontal directional drilling process

08.04.19 - Bialoleka, the northernmost district of Poland's capital Warsaw, marks the starting point of the Zeran canal (Kanal Zeranski in Polish), a man-made waterway that connects Warsaw's Vistula river with the Zegrze reservoir and, in turn, the Narew and Bug rivers. Averaging 25 m in width (reaching an impressive 41 m at its widest point) and measuring between 2.5 m and 3 m in depth, the canal flows from Warsaw's industrial port of Zeran along a course of 17.6 km, in places running parallel to the 633 main road, to reach the reservoir, situated close to the village of Nieporet. The canal passes through a lock (named after its constructor, engineer Tadeusz Tillinger) in Zeran and a weir in Nieporet. Along its entire length, the canal is crossed by one footbridge, eight road bridges and four railway bridges.

Spring water doesn't go far enough

Warsaw is known for its excellent subterranean spring water with more than 100 springs providing the city's inhabitants with drinking water every day. Since the spring water on its own is nowhere near enough to supply the city's entire population of two million, however, the municipal waterworks in central Warsaw treat the water from the Vistula to produce drinking water. Nevertheless, the routes to people's homes are long and the networks of pipes, which were built in the late 19th century, have aged and deteriorated and are in any case not nearly extensive enough. Very few of these old supply lines can be restored, with the majority having to be replaced time and time again with new piping, or in a bid to expand the existing network to incorporate more residential areas, completely new pipes have to be added to the system.

No other way round

One such new pipeline to supply water from Warsaw's municipal waterworks was planned for the suburban district of Bialoleka. This involved passing pipeline under both the Zeran canal at its widest point and the 633, the main road that runs parallel to the waterway. This was no mean feat for various reasons, with certain unknown quantities, namely the ground conditions and the course of other utilities, in particular a gas line and an electricity cable, giving cause for concern. With this stretch measuring around 200 m in length, laying a pressure line of ductile cast iron pipes (DN 500, 630 mm external socket diameter, construction length 6 m) under the canal and the main road called for trenchless horizontal directional drilling.

Preparing to go under

The company contracted to undertake the drilling work, the experienced and well-equipped Pabianice-based firm of Rutex run by Lukasz and Grzegorz Ruta, was in no doubt that this was a job for the GRUNDODRILL25N. Providing a power output of 190 kW and running on biodiesel, it is widely considered the ultimate "turbo drill". It makes light work of drilling tasks with 245 kN tensile and thrust force and a torque of 10,000 Nm. With a total weight of 18 t and a working width of just 2.5 m, the GRUNDODRILL25N was the perfect machine for the 200 m stretch under the canal and the main road in Bialoleka.
Ably assisted by Andrzej Wieszolek of TRACTO-TECHNIK, the specialists from Rutex decided which drilling tools to use and determined the composition of the drilling fluid. With no reliable information regarding the ground structure (geological layers/soil horizons) available, the general expectation was for loose sand and gravel, and the drilling equipment had to be chosen accordingly. This saw the team select a 150 mm diameter Soft Drill Head plus a bentonite suspension with a mixing ratio of approximately 40 kg/m3 for the drilling fluid – to act as a cutting and pumping medium, a lubricant and a coolant as well as a stabiliser for the 200-metre long borehole. The DCI F5 detection system was deployed for precision location work – a depth of almost 14 m was required at all times. Graduated backreamers were also on hand to expand three planned borehole clearings. Then all that remained to be done was to start drilling! Graduated backreamers were also on hand to expand three planned borehole clearings. Then all that remained to be done was to start drilling!

Problems are there to be solved

 The GRUNDODRILL 25N worked like a dream; the pilot bore (150 mm diameter) was executed perfectly thanks to the absolute accuracy and precision guaranteed by the 6-metre long cast iron pipe's maximum permitted angling of just 3.5% per socket. The machinery was guided through the sandy, gravelly subsoil with relative ease. Nevertheless, the pilot bore could only be drilled in individual stages, through no fault of the mechanical power or technology, but owing instead to the various other utilities that were located in unknown underground locations. Right at the very start of the drilling work, the machine had to be repositioned upon discovery of an intersecting DN 500 gas pipe – a discovery that caused much delay. Further (not insignificant) disruption to the pilot bore was caused by a power cable found under the road, the course of which could not be predetermined – this challenge called for extreme caution and finesse.
The pilot bore was completed as an interim step after an initial expansion to 440 mm using a Medium Soil Reamer. Two subsequent stages of expansion, to 660 mm and 860 mm, also used a graduated reamer before the ductile cast iron pipes were finally drawn into the bore hole. Since the water table was extremely high and there was a danger of the pipes rising up once drawn through the borehole, they were weighted down with water. With no hydrants available to fill the pipes, the water had to be transported specially to the site in additional vehicles, which was of course hugely time-consuming. Last but not least, the exit point to the bore path, right next to the canal, was very steep, causing further complications that had to factored into the schedule and the physical plans.

Two in one

In spite of all these complications and challenges, the entire build was completed in just four days, seven hours of which was the pipe installation itself. All those involved – man and machine – gave it their all to achieve great results that were reliable, fast and precise. Despite all the obstacles beyond their control, Rutex did an exemplary job and can now even expand their portfolio: Inserting ductile cast iron pipes is undoubtedly now a service they are more than qualified to offer. The GRUNDODRILL 25N from TRACTO-TECHNIK has proven itself once again: This time by passing under a waterway and a main road in one go.



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