Hardly any project will be as important and "the talk of the town" in Germany in 2022 as the construction of the LNG terminal from Wilhelmshaven to Etzel. Understandably so, because there is a lot at stake: Germany's first floating LNG terminal (LNG stands for Liquified Natural Gas), independence from Russian gas and ...
Hardly any other project will be as important and "the talk of the town" in Germany in 2022 as the construction of the LNG terminal from Wilhelmshaven to Etzel. Understandably so, because there is a lot at stake: Germany's first floating LNG terminal (LNG stands for Liquified Natural Gas), independence from Russian gas and around 30 kilometres of pipeline route. The Wilhelmshaven Link Pipeline, often simply called WAL, connects the floating terminal in Wilhelmshaven with the storage facilities in neighbouring Etzel.
Especially the short-term and time-limited construction of the terminals and connection lines poses great challenges for the client Open Grid Europe GmbH (OGE) as well as for politicians, authorities and participating companies. Right in the middle: Hölscher Wasserbau. For the so-called "Lot 2" with a length of 13km, we were commissioned to carry out the dewatering and environmental engineering. All in all, the 30 colleagues involved milled 11 kilometres of pipe trenches, drilled 500 wells with a depth between 8 and 12 m, laid 25 km of pipelines and realised about 60 open dewatering operations.
We are pleased that Hölscher Wasserbau was able to actively support the realisation of the new energy infrastructure and demonstrate its know-how.
Translated with www.DeepL.com/Translator (free version)
Work performance Hölscher Wasserbau:
- 11 kilometres of pipe trenches milled
- 500 wells drilled (depth: 8-12 m)
- 2 deferrisation plants up to 200 m³/h (throughput capacity)
- 3 booster stations à 200 m³/h
- Approx. 25 km of pipelines laid
- Approx. 70 special structures (road crossings / culverts)
- Approx. 60 open water stops
Photos: Open Grid Europe
"For half of the extensive construction project, Hölscher Wasserbau was commissioned with dewatering and groundwater management. For this, work was carried out simultaneously on 3 construction sites with 6 drilling rigs and a total of 60 employees..."
The European gas connection pipeline EUGAL runs in two pipeline strings over a length of around 480 kilometres from the Baltic Sea through Mecklenburg-Western Pomerania and Brandenburg to the south of Saxony and from there across the border into the Czech Republic. Due to the different geological and topographical conditions, dewatering is a complex undertaking to prevent the trench walls from collapsing again.
Hölscher Wasserbau was commissioned with the dewatering and groundwater management for half of the extensive construction project. For this, work was carried out simultaneously on 3 construction sites with 6 drilling rigs and a total of 60 employees.
To lower the groundwater level, about 2,000 wells were drilled along the pipeline, some of which had to cope with a water volume of 60 bathtubs per hour. In addition, drainage was milled over 44,660 linear metres and 3,500 linear metres of vacuum filters were installed.
"For the well-known major project Stuttgart 21, Hölscher Wasserbau raised the groundwater, pumped it via pipeline systems and purified it using treatment plants. To support the deeper natural mineral water sources, much of the purified groundwater was infiltrated back near the excavation pit..."
In the course of the construction activities for the large-scale Stuttgart S 21 project, groundwater is pumped, transported via a pipeline system to the treatment plants and purified there. To support the deeper-lying natural mineral water sources, a large part of the purified groundwater is infiltrated again near the construction pits. Excess groundwater is discharged into the Neckar River. The entire groundwater management system is continuously monitored and automatically controlled.
"Hölscher Wasserbau was commissioned to develop and construct drinking water treatment plants to restore the quality of drinking water in the region. In order for the drinking water to now be used again without hesitation, PFOA must be filtered out of the water..."
Over many years, the chemical PFOA (perfluoctanoic acid) has leaked into the groundwater through a nearby industrial park. Several tonnes of the harmful substance have entered the groundwater via the air and seepage water. In the Öttinger Forst area, drinking water for the surrounding communities and towns is drawn from the groundwater layers that have PFOA contamination. In this way, the chemical has also been absorbed by local residents and could even be detected in blood plasma. Hölscher Wasserbau was commissioned in October 2019 to set up appropriate drinking water treatment plants to restore drinking water quality in the region. PFOA must be filtered out of the water so that the drinking water can now be used again without concern.
A complex treatment plant was designed through which the water is purified from the chemical and meets the strict requirements for drinking water quality. The purification work of the constructed plant is divided into three pairs of filters, each with a working filter and a so-called police or safety filter. This division makes it possible to pump a water volume of 90l/s in the plant. Before and after adsorption in the filter, the water is treated by means of a disinfection stage. In these UV reactors, ultraviolet radiation destroys the DNA of any bacteria. In this way, on the one hand the activated carbon in the absorbers and on the other hand the water on the pure water side are protected from germs. More precisely, the water is pumped through the upstream UV disinfection via the supply line of the drinking water wells and then enters the working filter. After passing through the first filter, the water enters the police filter (also called safety filter) before finally passing through the second disinfection. From this point on, the water is called pure water and is available to the drinking water supply via the process route of an intermediate storage tank and a pumping station. When the activated carbon in the working filter has reached the absorption capacity of the pollutant, the safety filter acts as a working filter. The double design of the filter stages demonstrably guarantees the complete adsorption of PFOA as well as bacteria and pollutants. Afterwards, the loaded activated carbon can be changed and given for further recycling. The filterability of the activated carbon is regularly tested by independent accredited laboratories.
"In the course of the construction of the Elzmündung retention area, we have been commissioned with the construction of new wells and the subsequent expansion. The aim is to establish the infrastructure for an extensive groundwater retention facility in Baden-Wuerttemberg..."
In the course of the construction of the Elzmündung retention area, the state of Baden-Wuerttemberg, represented by the Freiburg Regional Council, is planning the construction of wells and pressure drainage lines as well as electrical and control lines. The project is part of the Integrated Rhine Programme (IRP), aiming at the construction of the infrastructure for an extensive groundwater retention facility.
"Before the foundations of the high-rise buildings are set, the groundwater has to be settled for a certain full stop of time. For this purpose, about 20 Quaternary wells with a depth of about six metres and 65 Tertiary wells with a depth of about 20-34 metres were drilled under confined space conditions..."
The large-scale FOUR project involves the construction of four new high-rise buildings with underground parking in the banking district in the middle of Frankfurt am Main. The skyscrapers are to reach a height of 100-228 metres and have a shared four-storey underground car park. The skyscrapers are to be converted into over 600 flats as well as the highest office floors in the country, a hotel and a day-care centre. The Construction will take place between Junghofstraße, Neue Schlesingergasse and Große Gallusstraße.
Before the foundations of the high-rise buildings are placed, the groundwater must be settled for a certain full stop of time. For this purpose, about 20 Quaternary wells with a depth of about six metres and 65 Tertiary wells with a depth of about 20-34 metres were drilled in cramped conditions. In addition, there are 25 control gauges/groundwater measuring points, 1000 metres of spur/ring/collector pipe and an elevated discharge pipe of 200 metres to the Gallus plant. The entire process was monitored by an elaborate monitoring and alarm system. The system consisted of automatically recording flow meters and data loggers for continuous monitoring of the groundwater level, which was lowered during construction. The special feature was the construction of the excavation pit using the cover construction method.
"In order to prevent the further spread of groundwater contamination towards the excavation pit, the specially developed and patented hw-dsi process was used..."
A new laboratory building for the Osnabrück University of Applied Sciences is to be built in Lingen. In the process, the contamination of the groundwater with cyanide was discovered. Hölscher was commissioned to prevent the cyanide contamination from spreading into the groundwater so that construction work on the campus could continue.
In order to prevent the further spread of groundwater contamination towards the excavation pit, the specially developed and patented hw-dsi® method was used. The 30 DN50 nozzle suction infiltration wells at a depth of 13 metres create a hydraulic barrier about 140 metres long that shields the damage. Between 25-30 m³ of water are thus infiltrated per hour. The wells are equipped with MID water meters and allow real-time monitoring of the infiltration volume. This means that if the groundwater level fluctuates, it can be readjusted and readjusted if necessary. The challenge here is the narrow efficiency of the barrier, which makes detailed monitoring necessary, as well as the locally varying infiltration capacity. Comprehensive calculations and tests were therefore necessary in advance. These were carried out using a geohydraulic flow model with Visual Modflow software.
"In order to enable dry excavation work and to secure the shaft bottom against uplift, the groundwater had to be lowered internally. For this, a total of about 1100 wells with a depth of up to 45 metres were drilled for groundwater extraction..."
The Cityringen metro in Copenhagen is a 15.5 kilometre long, twin-tube tunnel system with 17 underground stations and an underground maintenance depot. The Cityringen line consists of two tunnels, each 5.78 metres in diameter. The tunnel tubes run at depths of up to 25 metres below the earth's surface, mainly through Copenhagen limestone. In addition to the TVM drives, 22 shafts with a depth of up to 30 metres were built.
"In the course of further property protection, flood protection with a height of more than 6.5m above normal zero is required. For this purpose, a flood protection wall made of steel sheet piles has been built and further 27 gravity wells have been put into operation..."
Weser Stadion GmbH needed a flood protection with a protective height of +6.5 above sea level in the course of further object protection. To achieve this goal, the construction of a flood protection wall made of steel sheet piles is necessary. Furthermore, the construction of 27 gravity wells is planned. These wells will be controlled by level measurements and the groundwater produced will be fed into the adjacent Weser River via a pressure pipeline. The end result is a dry playing venue for the players of SV Werder Bremen.
27 gravity wells DN 700/315 were constructed to a depth of 12 metres, and the wells were developed using high-performance filter slots. 27 submersible pumps with a capacity of 75m3/h to 150m3/h were installed in them. In addition, a riser and piping were installed up to the top of the well. To control the system, an EMSR interface to the stadium's system was integrated.