GRUNDODRILL 18ACS installs 1,739 m drinking water pipeline

09.01.20 - Briefly, those are the key figures regarding a tricky construction measure, completed almost on the doorstep of TRACTO-TECHNIK’s headquarters in Lennestadt. The climate health resort Lennestadt-Saalhausen, situated in a green valley along the River Lenne – one of the most beautiful and densely forested villages in the Sauerland area of North Rhine Westphalia, was the “Scene of the incident” for a short time. Despite the idyll, the drinking water was in danger of being in short supply due to the previous year being extremely hot and dry. Therefore, a modern and sufficing drinking water network was the highest priority.
  • Location: Lennestadt-Saalhausen / Germany
  • Task: Underground construction of a 1,739 m drinking water pipeline with simultaneous installation of cable protection pipes along a bicycle path
  • Client: Lennestadt Council in unity with the GUV Kassel
  • Contractor: H&E BOHRTECHNIK, Bolberg/Thüringen lead by Reinald Engst
  • Course of events: 19 successful single bores in rock and four times crossing underneath a river to install the 1,793 m length PE-100-RC drinking water pipeline, as well as telecommunication data cables over a section length of 790 m 
  • Resolvement of incident: with 100% success

The bore path is not an ideal trail

Lennestadt Council had already assigned the company GUV Geohydraulics in Kassel with the planning to install a drinking water supply pipelines part of modernising the water supply in Saalhausen in 2017. Due to the construction of a new drinking water treatment plant, a simultaneous new construction of the drinking water pipe had become necessary. This also presented the opportunity to install a telecommunication data cable at the same time. The intended bore path was not exactly an ideal path: tight conditions along a bicycle and hiking trail, 4 times crossing of the River Lenne, several road and path crossings and last not least, quite difficult soil conditions.

The crew is optimally equipped

There was soon no doubt, that the 1,793 m long supply pipe (1,003 m PE-100-RC Pipes OD 180 and 790 m PE-100 RC-Pipes OD 140, including 790 m HDPE Cable protection pipes OD 50 to retain a data cable) for natural conservation reasons, cost efficiency, influence on traffic and cyclists/hikers and not least for technical reasons (e.g. under crossings) could only be carried using an underground construction method, in this case HDD. There was also no doubt that H&E Bohrtechnik GmbH from Bollberg was the most suitable partner to carry out this project. Since 2005 the company has been a specialist for horizontal directional drilling and their team is in great demand where traditional civil engineering reaches its limits. Furthermore, they have a considerably well-equipped machine and equipment fleet. With six HDD rigs in various configurations and performance categories as well as the technology for suction and disposal of the drilling fluid at their disposal.

The “King of Rock“ is sorely needed

Right from the beginning, it was pretty clear that only an HDD rock drilling system could be applied, as the core bores for the geological survey had unearthed mainly solid rock (slate) with tight gravel, sandstone and/or hillside loam and talus. This meant high demands for the professional borers as well as the machine. The drilling operation for the installation of the 1,793 m length drinking water pipe and the data cable were clearly a task for the GRUNDODRILL 18ACS – known as “King of Rock” and not for no reason at all. The “King of Rock” has liven up to its name in numerous, comparable construction projects. It is extremely powerful with a compact construction, allowing the best possible adaption to all soil conditions, can be adapted quickly from rinsed boring to rock drilling, is equipped with a fully-automatic drill rod loading system and provides maximal productivity in all rotation speeds.

The bores are definitely no pushover

The H&E bore crew, with their experienced bore rig operator Steffen Hellfritzsch and construction manager Reinald Engst, could slowly start working on the practical side and determine any further equipment required for the bore process: The 6 ½″ roller chisel, IADC-Code 527, is driven by the ELICON 95 twin-tube rod, which allows maximal rinsing quantities (up to 400 l/min), even over long bore lengths. For the expanding bore channel they chose to apply a 
12″ hole opener and for the bore rinsing – as a greasing, cutting and feeding medium, as well as bore hole stabilisor – they decided to use a Bentonite suspension (25 kg/m³).
After the bore tools and the composition of the drilling fluid had been determined, the GRUNDODRILL 18ACS was positioned, the first starting and target pits excavated and the PE 100 RC-pipes OD 140 ready for installation, they were finally ready to start the first pilot bore. The driving force from the inner rod to the bore chisel reached an average of 1.500 Nm, the average pushing and pulling force was 35 kN (maximally 75 kN), the length of the bore was 144 m. A 12″ hole opener had to be applied, in order to expand the bore channel. This was followed by the pulling-in process of the PE-100 drinking water pipes and the HDPE cable protection pipes to accommodate the data cable later. These were prepared on the exit side of the borehole, connected to a 10″ backreamer and pulled into the bore channel successively.

The soil conditions were “the culprits“

In this rhythm 19 single bores were created with 21 starting and target pits for the water supply line to the Water Works Lennestadt-Saalhausen of 1,793 m length, including 750 m cable protection pipes for a data cable. During the bore process, several roads had to be crossed under and the riverbed of the River Lenne four times, which winds its way through the village. The difficult and complex soil conditions, which are typical for this region, are reflected in the duration of the bore work: for the above mentioned 144 m long bore, the well-coordinated team took a good six days. H&E Bohrtechnik mixed a total of 459 m³ Bentonite for the 19 single bores, 271 m³ of which were treated with the company's own recycling unit and 188 m³ were disposed of expertly.

The supply is secured

The beautiful Lenne Valley in Saalhausen has been an acknowledged health resort for over 45 years, with spa gardens and large ponds, Kneipp facilities, as well as numerous hiking and cycling paths between the fields and forests. Nevertheless, even here, the dry summer of 2018 had left its traces. The drinking water was in danger of running dry. A fatal situation for a lively holiday and air health resort with Kneipp facilities. How good it is that a secure supply of drinking water to the village has now been created and thanks to modern technology even without any noteworthy interferences for the Spa, holiday and everyday business – an almost unnoticed incident.



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