A new quay wall was built at the B2 Canal dock in Antwerp by order of the Antwerp Port Authority. The more than 800-metre-long quay wall is one of the heaviest in Belgium and is suitable for a water depth of up to 17 meters. The new quay wall ensures that larger and deeper ships can now moor.
Ghent Dredging dredged the zone between the old and the new quay wall, and the zone in front of the old quay wall, to a depth of -12.5m TAW. The Company Aertssen, our partner in the Temporary Trading Company, took care of the dry earthwork between the old and the new quay wall. Over the entire length of the quay wall, this meant a dredged volume of no less than 1.4 million cubic metres. At the same time, the old quay wall was also demolished step by step.
The work had to be completed in a record time of 30 weeks and that was also successfully achieved. Ghent Dredging used its cutter suction dredger “Ouistreham” and its two largest dredging pontoons GDVI and GDVII for this purpose. At the height of the yard, 20 barges were at work to transport all the dredged land to various destinations.
The entrance of the Port of Blankenberge has been dredged several times by our CSD Ouistreham.
A quantity of 1,077,000m³ has been dredged, transported by barges and pumped into spoil areas.
Although a maintenance dredging contract, it also included straightening out a bend in the canal at Beernem, including bank protection work on the newly formed embankments.
Between Aalter and Beernem, as well as at Bruges, war ammunition was found during the dredging operation. To cope with this particular problem, the dredged material was separated from the ammunition by use of screening. Dredged material washes through the screen, whereas the ammunition remains behind on top of the screen to be disposed of.
At Bruges it took us 3 months to finish this operation, while the other location took 6 months.
Among the war ammunition removed, we found hand grenades, air bombs, mortar-shell and devices containing lethal gasses.
Ghent Dredging has been awarded by the "Ports Normands Associés (PNA)", the contract for the dredging of a new turning basin for sea ships on the canal from Caen to Ouistreham (FR). With our cutter suction dredger, we dredged 200,000m³ of sand to a distance of 2,200m. The sand was pumped into two sand fill areas that we constructed before the start of the dredging work.
Upon completion of the upgrade of the embankments, dredging work started to allow ships of up to 3,000 tonnes on the river Deûle.
Stage 1 consisted of dredging the downstream part of the river. The majority of the dredged silt has been deposited in the designated spoil areas near Quesnoy-sur-Deûle. After completion of this spoil area, clay ground was used to cover the silt. Finally, recovered topsoil from the spoil areas was put on top of the clay to enable these areas to be refurbished into a new green area in the near future.
Another part of the dredged materials was shipped to a designated spoil area some 100km away near St. Omer.
Maintenance dredging of the river Durme started for our client Waterwegen and Zeekanaal. The purpose of the contract was twofold:
a. To enlarge the cross-sectional area of the river and, by doing so, to reinstate its discharge capacity.
b. To create 3 stockpile areas with sand for future use in ring dikes of inundation areas to be build along the banks of the River Durme.
A quantity of approx. 400,000m³ was extracted from the riverbed . The dredging was carried out by our CSD Ouistreham. The sand was transported through a floating and a land-based pipeline over a distance of up to 2,500m in the stockpiles called Bunt, Klein Broek and Groot Broek.
Dredging effectively started after the construction of the bunds of each fill area. The end of the area to be dredged was approx. 500m upstream of the historical Mira bridge at Waasmunster.
The silt was dried by active lagooning and was disposed of at a later stage at an allocated depot.
Ghent dredging executed the maintenance-dredging operation on the Canal d'Hazebrouck.
After a long tender procedure (most economically advantageous tender), this contract was awarded to Ghent Dredging based on its technical and financial proposals by client USAN (Union des Syndicats des Assainissement du Nord).
A total quantity of approx. 18,000m³ of heavily contaminated silt was dredged and disposed of at Ghent Dredging's soil-treatment centre at Ghent.
Dredging was carried out using a so-called "Menzimuck” digger. Excavated soil was transported along the canal in 40m³ barges, pushed by 4 small boats. The spoil was reloaded by a digger into lorries with watertight containers and transported to Ghent. To enable the digger to unload the barges, a temporary bridge across the canal was constructed.
Upon completion of the dredging work, a 250m-timber sheet pile bank protection was placed in the urban area in the centre of La-Motte-au-Bois. Finally, the road on top of the embankment was resurfaced.
Upon completion of the dredging contract, the client proceeded with the entire refurbishment of the embankment of the canal.
For many years, no maintenance dredging had been carried out on this canal due to a lack of funding. Finally, a budget was allocated to dredge the canal to such an extend that a restricted shipping passage was created. About 50% of the contract, at the Ypres side of the canal, has been carried out by Ghent Dredging.
This contract can serve as a perfect example of how our dredging and environmental divisions complemented each other.
Dredging was carried out using a pontoon mounted on a 14-tonne excavator.
Elevator barges loaded with silt were discharged alongside a pontoon equipped with an excavator fitted out with a DOP-1815 dredge pump. After adding water to the sludge, the pump discharged the silt into dewatering areas.
Once inside these areas, dredged silt is pumped into geocontainers fitted with polymers. The addition of polymers accelerates the dewatering process, with the silt turning into soil after a couple of days.
The Roubaix Canal Dredging Scheme between the Belgian-French border and the River Deule was carried out as part of the European Union funded 'Blue Links' project.
Some 160,000m³ was dredged on both the Roubaix Canal and the River Marque. Included in the contract was the construction of a dewatering area, divided into three separate catchment areas on top of the waste mountains created in the by the local gypsum industry at Wattrelos.
The bottom layer of the basins consisted of bentonite matting and drainage material. The effluent was discharged through this drainage system.
Additionally a 1,200m² consolidation area was created to catch the effluent originating from the dewatering areas. Analysing and disposal of this water was conducted in accordance with French environmental legislation.
Also included was the construction of two quay walls to allow for truck loading of the dredged material.
Dredging was carried out using two small backhoe dredgers and a fleet of small barges. An average daily output of 450-1,000m³ was achieved.
Subsequently, another 20,000m³-capacity silt area was created adjacent to the E17 motorway embankment. Its 40,000m² surface has been waterproofed entirely with an MRC membrane as well as an external drainage system to allow analysed water to drain back into the canal.
Finally, site known locally as the PCUK site was used to dewater approx. 130,000m³ of silt with a reduced water percentage of 30%.
A maintenance contract was carried out for our client SPW (Département des Voies Hydrauliques) on the Spiere Canal, starting at the French-Belgian border up to the upper reaches of the River Scheldt.
Along a distance of 8 km, a total quantity of 45,000m³ of polluted silt was dredged and transported to the Upper Scheldt in small barges. From there, the silt was reloaded into bigger barges.
The dredged material was then transported another 25km upstream to an SPW-owned lagoon. Unloaded by a long-reach digger, the silt was ultimately hauled with water-tight dump trucks to the lagoon.
After consolidation, the silt was then finally disposed of by means of barges in yet another depot.
After having carried out dredging works on the upper reaches of the Spiere Canal (Canal de Roubaix) and the River Marque on French territory for our client VNF (Voies Navigables de France), the Upper Scheldt is once again - after 30 years - connected with the River Deûle.
The fully restored canal was inaugurated in the presence of a great number of dignitaries from both France and Belgium. The ceremony featured the first pleasure craft to sail again along this historical waterway that is such a part of our heritage.
Rouen Port Authorities awarded JV Ghent Dredging-Dutch Dredging the contract to enlarge and deepen the turning basin at Hautot-sur-Seine (about 10km downstream of Rouen). The contract is part of the Port's programme to deepen the river Seine from Le Havre towards Rouen by one meter to make the port accessible to larger vessels.
The contract comprises the removal of approx. 800,000m³ of sand, silt, gravel and limestone. The dredged materials are transported by means of tugs and barges over a distance of 30 km to Yville-sur-Seine. At Yville-sur-Seine, a barge-unloading dredger empties the barges and disposes of the materials into various fill areas over a distance of approx. 1km.
The main features of the project are:
A maintenance dredging contract on the Canal Neufossé between Dunkirk and Valenciennes has been carried out on behalf of our client VNF. Some 110,000m³ was taken out at the time. Twelve years on, a similar contract has been awarded within the same area. This time about 150,000m³ has been removed. Both times similar equipment was been used, i.e. a dipper-dredger, tug, dry-well barges and a barge-unloading dredger.
Included in the contract was the (re)-creation of a 25-acres fill area, taking into account additional measures regarding the existing surrounding environmental areas, such as earthworks, sealing of the fill area, overflows, etc. The discharge of the dredged material was carried out using a closed-water circuit to avoid the loss of material into the canal.
Ghent Dredging was commissioned to realize a new lock in the Polder of Lier. This polder, with an area of 156 hectares, is made for the water management around the Nete. The flood control area is part of a chain of flood plains along tidal rivers that will drastically reduce the risk of flooding. When the Nete bursts its banks, the Polder will act as a buffer basin for the storage of water. The construction of the larger lock ensures that the water can drain from the area more quickly, so that there is more capacity to collect water again.
In addition to its water management function, the Polder will also fulfil an ecological task. Water comes in every day at high tide and at low tide the lock will drain the water back to the Nete. The wilding of the polder in this area provides the ideal habitat for numerous plants and animals. An ecological pool is being constructed near the lock. This pool, together with the canals and creeks, ensures that there will be permanent water in the area, which will greatly increase the biodiversity in the area.
In addition to the construction of the new drainage structure, the overflow dike and the surrounding infrastructure were also renovated. The overflow dike was covered with open asphalt, which ensures that no washing out occurs when this dike is flooded. This open asphalt has the characteristic that it is a porous material, permeable to water and allows grass and plants to take root in it. The cycle path along the Nete was redeveloped and now provides a smooth connection between Lier and Mechelen.
Since the new downstream weir is subject to erosion in various places, several local repairs had already been carried out in the past. These repairs did not yield the desired result, however, as erosion continued to occur.
This assignment consisted of two major parts:
Local break-up of the existing penetrated armour stones up to 3 tons and restoration by means of a solid concrete slab with a thickness of 1.40 m. The concreting of the concrete slab consisting of 1,425m³ was realized in one day.
The new dam with a total length of 480 metres and a surface area of 12,500 m² had to be dredged in order to realize soil protection consisting of a geotextile with wedges and armour stones 5/40 penetrated with colloidal concrete.
The Graan Dock was closed off using a steel combi-wall. The area behind was filled in with spoiled sand. The purpose of the project was to create new dock areas to replace the old dilapidated dock.
The dredging and filling part of the contract was carried out by Ghent Dredging as a subcontractor to main contractor Besix nv.
The dredging operation comprised the removal of a layer of polluted silt from the old dock and the disposal of it in our lagoon at Ghent, as well as dredging non-polluted material to be re-used in underwater areas at the Churchilldock in Antwerp.
In advance of the piling of the combi-wall, soil-improvement with sand was carried out . To do this, the area was dredged up to 18m below water level.
After construction of the combi-wall by the main-contractor, the old Graan Dock was hydraulically filled in with layers of required specified sand of 30cm.
This sand was hauled from an existing stockpile by dump trucks. Using a temporary bridge, the lorries dumped the sand into barges. With the deployment of our barge-unloading Rhosnes, a mixture of sand and water was pumped through a 400m-long floating pipeline to a spraying pontoon. With the help of an RTK positioning system, sand was sprayed in 30cm layers.
To meet the stringent compaction requirements the whole area was compacted using a heavy compaction device.
A total quantity of 160,000m³ was to fill the entire area .
As part of the rehabilitation works of the "Perré Risban" forming the access channel to the outer harbour west of the port of Calais, Ghent Dredging has been assigned the bank protection works, whilst our partner, Spie Batignolles, has executed the civil engineering works.
With a length of 460m, the existing "Perré Risban" consisted of an anchored sheet pile wall, supporting a layer of sandy marl protected by a reinforced concrete slab. The "Perré Risban" in its present design dated from the 1970s. The sheet pile construction has been heavily corroded, causing many disorders (fissuring of the slab, flow of fine materials).
The adapted solution is a new combi-wall (combination of sheet piles with H-profiles) standing autonomously in front of the existing sheet piles, and the infill of the space between the sheet pile walls. This way, the existing sheet piles no longer play a role in supporting the embankment.
The new construction is protected against waves by a layer of quarry stones 1/3T.
Our work consisted of:
To realize our scope of the contract, two sets of equipment have been deployed:
A total quantity of 16,000m³ quarry stone, 8,000m² geotextile and 10,000m³ backfill has been incorporated.
The scour-protection at Pier n°8 has been refurbished as preparation for the arrival of the latest generation of super-ferries.
The existing protection had to be removed (and dumped at high tide on the beach to be recovered at low tide) and the surrounding area deepened. Upon completion of the dredging operation, the new rock armour scour-protection was placed.
Work has been carried out within a tidal window of approx. 7m, resulting in a working depth of 18m below water level at high tide.
To allow for a reduced layer of rock armour, stones with an extremely high density of 3.15 t/m3 have been used. Due to its high density, this rock armour cannot be found in local quarries and had to be imported from a quarry in the Vendée area in France and transshipped through the port of Sables d'Olonne. A total quantity of 14,000 tonnes was used to achieve the required result.
The banks of the river Deûle have been realigned and strengthened stretching from the French-Belgian border upstream towards Lille.
Voies Navigables de France has awarded joint-venture Ghent Dredging - Soetaert this contract to realign and reinforce both banks with sheet piles, gabions and rocks over a distance of 20km.
The project is part of the widening and deepening of the river Deûle to upgrade inland shipping to CEMT-class V, enabling ships of up to 3,000 tonnes to use this waterway. The actual widening and dredging works were also partially carried out by Ghent Dredging.
The upgrading works of the river Deûle in the north of France to CEMT-class V is part of the Seine-Scheldt Project of which the masterpiece of the entire project will be the new canal between Cambrai and Compiègne.
To be able to carry out the works, the existing banks were cleared of trees and bushes and the existing stone protection removed.
After vibration of the sheet piles (in general up to 1m below water level), the new banks have been built up with rocks, size 20/80 kg to approx. 1m above mean water level. The remainder of the banks have been graded with (top) soil and reseeded.
Non-exploded ammunition was found in the downstream area between Deûlémont and Quesnoy-sur-Deûle. After thoroughly side-scanning both banks, the decision was made to reconfigure one of the diggers with a safety-pack to allow for safe dredging and recovery of non-exploded ammunition found within the sheet pile area.
In the upstream part within the Lille area, works were to be carried out in an urban area. Problems arising from working in build-up areas, such as working in confined spaces, underground cabling and the many bridges, created obstacles to be dealt with. These circumstances necessitated the use of special techniques such as the construction of an underwater cutter soil mix wall of 500 metres.
Some areas have been built using gabions. Existing gabions in deplorable condition have been removed and replaced with cubic gabions 1m by 1m on top of a foundation with gabion mattresses.
At Blaarmeersen Estate, along its famous watersports area, the beach area has entirely been refurbished.
After preliminary works, earth works were carried out, including a new sewer system and paving. Completing the contract called for the truly visual results: the construction of the esplanade, water slide, sanitary facilities, a pedestrian bridge and the ever-present joy for children: toys!!!
And this all to the satisfaction and the happiness of the citizens of this beautiful city.
After nearly 60 years, the redundant filled-in connection between the Lys and the Scheldt has been reopened. The existing parking area and the existing plants have been removed. The old quay walls, hidden under the pavement, have been exposed and tested for their stability. It was decided to partially upgrade and partially renew them.
At the Reep side, a completely new quay wall has been constructed using a secant wall covered by masonry brickwork . The existing quay wall at the Diocese Quay side was cleared and reinforced by means of micro piles and HDI piles. In addition, a new quay wall was cast in concrete, finished with masonry at the front.
At the same time, the infrastructure, such as the sewage system and roads of the Reep, the Diocese Square and the Diocese Quay were completely refurbished and finished in cobblestones.
At the refurbished side of the Diocese Quay, a low-level quay was made in Belgian blue stone to create a secluded area to relax.
The final phase of the works was the further excavation of the formally filled-in part of the river Scheldt. The reopening of the Lys and Scheldt connection, after so many years, was extensively covered by the local and national media and was the subject of many festivities.
The many years’ experience of our skilled employees were required to successfully complete the project as a challenging combination of various disciplines (road construction, earthworks, hydraulic engineering and dredging works) and has made the Diocese Quay-Reep zone one of the nicest places in Ghent.
Client Maritieme Toegang and Port of Ghent had awarded JV Besix-Ghent Dredging the contract to provide a scour protection at the Moervaart at Ghent.
Located at the utter downstream part of the canal, 2 types of scour protection were placed over a total length of 900m alongside the northern quay walls.
The purpose of the contract was to reinstate the scour as a result of shipping traffic, causing an imminent stability problem to the quay wall.
The second goal was to dredge the waterway.
TYPE 1: rock-armour
Over a length of 450m by a width of 24m, a (temporary) bottom protection at variable depths was carried out using stones. Firstly over-depths in front of the quay wall were filled out using steel slag material size 32/90 mm, covered by a layer of armour stones size 10/300kg and partly penetrated with colloidal concrete.
TYPE 2: Asphalt mattresses
In the zone to be covered by asphalt mattresses, the area had to be dredged in advance up to the solid sub-strata.
Before any mattress could be placed, deeper areas were filled out with steel slag material size 32/90mm.
After levelling, the full width of 20m was ready to be covered by asphalt mattresses. Alongside the toe of the channel, the edge was protected with a layer of stone, with a width of 4m.
Sealing alongside the quay wall was established using colloidal concrete.
Finally the main channel was again dredged to the required depth. The dredged material, sand and silt, were disposed of at the Rodenhuize lagoon area.
The mattresses, measuring 10 by 5m, were fabricated at the adjacent Moervaart quay area in a 120m by 18m working area. For that purpose the existing road had to be realigned locally.
In the working area itself a number of 20 sets of prefab form work units have been erected.
After positioning the steel wire webbing each form work was filled with a 30cm layer of asphalt. The asphalt in each form work was then levelled with a beam to achieve an even layer.
Using a specially designed hydraulic lifting frame designed by our subsidiary Deco nv, and in combination with a 160-tonne crane, the mattresses were lifted from the quay and stockpiled onto a pontoon.
After positioning the mattresses were placed using the frame, equipped with a RTK positioning system with one-centimetre accuracy on top of the steel slag foundation. The seams between the individual mattresses were sealed using hydro-mortar.
In all 21,300m³ of silt were removed, 10,560m² of asphalt-mattresses placed, about 11,000m³ of steel slag used and 17,670 tonnes of armour stones incorporated.
As a sub-contractor to Visser & Smit Hanab, a twin submerged pipeline has been placed near Ghent-Muide, consisting of two steel pipelines (dia. 500mm) designated to the transportation of gas.
The contract included the construction of the two receiving steel-piled boxes on both banks, dredging the required trench and assisting the main contractor during the operation to submerge the pipelines across the Houtdok.
Also included was the refill of both the trench and the receiving boxes and the renewal of the quay walls along a restricted length of the Houtdok.
At provincial Gavers Estate, a beach of just over 6,000m² has been created, including sports and leisure facilities.
To allow for dry excavation, a temporary bund has been constructed across the pond. After completing this bund, the pond became the perimeter of the protected swimming area. Finally, additional works related to recreation completed this contract.
At Harelbeke, County Estate "de Gavers" has been thoroughly renovated with the construction of a new poolhouse, the reinstatement of a diving site, a renewed riverbed for the Gaverbeek watercourse, a new reception building and a brand new watersports building.
Ghent Dredging has been involved in all of these activities in various phases of the contract. Our part in the upgrading included:
Some years before, Ghent Dredging started works at Gavers with the construction of a restricted swimming area, consisting of a sheet-pile wall and a concrete floor. On top of the sheet-piles, a steel construction has been jointed to serve as a support of the timber bridge around the swimming area.
At Lixhe, near Liege, we have been awarded the contract by the regional Rivers and Water Authorities (SPW-Voies Hydrauliques Liège) to reinstate the scour protection at the downstream side of the Lixhe weir.
About 30,000m³ of the existing scour protection had been washed away during periods of extreme water flow on the River Meuse. The void that had occurred was threatening the stability of the weir.
The execution of the contract was limited by various restrictions:
Due to its extensive experience, Ghent Dredging was able to carry out this contract. Local quarries were used to produce the 54,000 tonnes of stones required. The imported rock was discharged at the upstream side of the weir, loaded onto dump trucks and, at the downstream side loaded onto a split barge.
The split barge was positioned by the use of a spud-legged pontoon, mounted with a 50-tonne digger, equipped with a DGPS positioning system, enabling the accurate placing of the various sizes of rock.
The rock had to been placed into 3 different layers with 3 different types of stones, i.e. 10/250kg, 450/1000kg and 1000/3000kg.
At the Zandpoortvest at Mechelen the Binnendyle has been opened up again after 40 years. The existing car park between the two buildings of the Thomas More College has been converted into a green, open meeting place with gently sloping banks and a jetty.
In order to realize this work, a work platform was first constructed in the river Dyle. This was to that the construction of the required secant walls could be reached. Anchored secant walls were built to guarantee the stability of the adjacent road once the banks were dug out. After the finishing of the secant walls, the concrete walls including its coping were realized. These were required, among other things, to be able to realize the requested wheelchair ramp up to the lowest square.
Once this was done, the concrete channel could be demolished. First the roof of the tube was scalped, and subsequently the walls were sawn through and removed. The lower part of the existing channel still serves as a riverbed.
In the final phase of the contract the conversion was completed by removing the existing banks, rebuilding the sewage system and the casting of a concrete foundation to be completed with a staircase in natural cut-stone steps.
The finishing touch is the paving of an 1.800 m² area in Chinese granite.
At Monceau-sur-Sambre Ghent Dredging carried out repair works at the downstream side of the weir and its scour bed.
The reported damage:
The location where the damage has occurred made a hard job to repair with:
The job in hand consisted of:
To carry out the job a self-propelled pontoon, mounted with a 20T digger, equipped with DGPS was used.
The pontoon had to be modified several times to be able to carry out the various stages of the contract, i.e. dredging, rock dumping, incorporating concrete and fixing both banks.
Some quantities:
At the Mortagne-St.Léger section of the River Scheldt its riverbanks have been refurbished as part of a contract awarded by the French River Autority (VNF).
Approximately 15km of riverbanks have been refurbished using 46,600m² of filter fabric and 75,000 tonnes of stones. About 88,000m³ of soil have been shifted.
In global 15.2km of shore had to re-profiled. Also 46,600m² of geotextile and 75,000 tons of rocks were placed. As a finishing touch, 125,000m² was sowed.
There was a complete soil transport of 88,000m³.
For many years this area has served as a water storage area to the surrounding textile mills. After the demise of the industry it soon turned into a neglected and rapidly deteriorating area. The area itself was covered in weeds for many years. Some time ago the decision was made to turn it into a public area.
After emptying the basin, the contaminated silt has been removed, its banks reshaped and furnished with a stony bank protection. At both ends steps have been constructed bordering an artificial waterfall. Slopes provided with shrubs and an agreeable public lighting turned the area into an intimate walking space.
The finishing touch was the installation of a beautiful bridge midway the basin to be used by pedestrians and bikers.
The Flemish Environment Agency is working on an integral redevelopment project along the Zuunbeek in Sint-Pieters-Leeuw. The works will limit the flooding in Negenmanneke and promote the ecological and scenic recovery of the Zuunbeek.
In the past, the natural catchment area of the Zuunbeek was mainly adapted to, for example, supply the existing water mills with sufficient water. About forty years ago, the stream was straightened and deepened to allow a speedy discharge of excess water. Wetlands were filled up and paved areas, such as new roads and houses, increased. The accelerated drainage and the increased paving was the cause of increased flooding downstream at Negenmanneke.
De Zuunbeek and her valley are now better equipped. There will be more room for water storage by making the brook meander and by creating flood plains. Meanders ensure diversity through steep and soft banks, deep and shallow parts. That way, there are parts where the water flows faster and more slowly. This increases the self-cleaning ability of the watercourse and increases the biodiversity in the stream and its banks.
The works have been divided into four sub-projects, of which Ghent Dredging has carried out the first sub-project Volsembroek.
At the beginning new meanders have been dug. The straightened Zuun has been filled up in some areas, but in most places the straightened Zuun has been retained and will serve as an emergency overflow and storage at high water levels. Upstream of the project area no new meanders will be dug, but "flow deflectors" have been placed in the water.Due to these obstacles in the water, the watercourse is forced to find a different route and, as a result, the watercourse will begin to wriggle itself.
A new dam was built near the existing Volsem storage basin. This can regulate the water level upstream. In addition, a dike was constructed to allow the nature reserve behind the dike to serve as a controlled flood area during heavy rainfall. This flooding area has a capacity of 204,000m³.
OVAM assists schools with soil investigations and remediation. The purpose of this is to map polluted school grounds and to support schools administratively, practically and financially with soil investigations and soil remediation of their grounds. For a primary school in Bottelare, Ghent Dredging has carried out soil remediation on behalf of OVAM.
At this school, a leaking underground fuel oil tank of 15,000 liters has caused soil contamination with mineral oil. The tank was located in a built-up courtyard of a historic building. The buildings inside the courtyard had to be demolished. Originally it was also planned to tear down the wall on the street side. However, this was not allowed.
Taking into account the location of the tank in the courtyard with the limited passage, space and the stability technical (boundary) conditions, a shoring technique was sought that was practically feasible. Ultimately, it was decided to install a tangent pole wall, equipped with a smaller machine that could pass through the passage.
In order to be able to carry out the excavation in the dry, the groundwater was lowered. The pumped-up groundwater was purified by a mobile water purification unit before being discharged into the sewage system. After the pile wall had hardened, the 15,000 liter tank could be removed. In order to be able to evacuate the tank through the passage, it was burned in 3 pieces.
After this, the contaminated soil could be excavated to a depth of 3.5 m and transported via containers to our GSC Rodenhuize in Desteldonk for processing.
After refilling the construction pit with filling sand from another Ghent Dredging site, the courtyard could be finished in function of the repurposing, ie a courtyard garden.
The facades, released after the demolition of the veranda construction, were repaired and a number of doorways were bricked up. The facades were finished with limestone and plaster. This was combined with the already planned replacement of the windows and doors.
Thanks to a good collaboration of all parties involved with Ghent Dredging (OVAM, school, EBSD and the municipality of Merelbeke), the works, which were carried out in a busy school environment with an important intake of the public domain, could be carried out in a smooth and safe manner.
In this project, the core of a historical contamination with VOCl in the solid part of the earth and in the groundwater was tackled at a site in Ghent (the former laundry-dry cleaning "Wasserij der Vlaanderen").
Civil engineering works were carried out in a first phase: internal excavation with stability measures up to 3.50m with drainage and GWZI, batch excavation with addition with stabilizer. During the excavation, a well was found in which highly concentrated contaminated sludge was found. This turned out to be the main source of the contamination. In the end, approximately 700 tonnes of contaminated soil and rubble were transported to our soil and sludge processing center GSC Rodenhuize.
Phase 2: to stimulate the biological degradation of the contamination with chlorinated solvents, we installed a recirculation unit for groundwater on behalf of OVAM.
Groundwater recirculation was provided with the addition of carbon source and bacterial inoculum. The great advantage of this technique is a homogeneous distribution and mixing of the carbon source. 4 Extraction filters in the center of the core zone and 8 injection filters on the edge of the core zone were drilled. Injections were also made into two drains placed just below the excavation level. The injection and withdrawal filters were fitted with a 5-10 m filter stage.
On the one hand, in order to chemically tackle the high concentrations of per and possibly pure product and in this way to improve the redox conditions for biological degradation, zero-valent nano-iron was injected before the start of recirculation via direct push.
After the iron injections have been carried out, the anaerobic recirculation can be started. For this purpose, groundwater is pumped up at a flow rate of approximately 2 m³/h by means of an underground well pump and back infiltrated via a collector to 8 filters at 0.25 m³/h per filter. Flow meters and dosing points for substrate and bacterial inoculum are present on the collectors and pipes.
The collector and the other components were mounted on a board within the defined excavation zone in the laundry. The necessary sampling points are provided.
After a recirculation period of one year and sufficient addition of substrate and inoculum, (geo)chemical and bacteriological monitoring data show that the conditions for the degradation process of the contamination with tetrachloroethene are favorable and that the process is well under way. The concentrations of VOCl have fallen sharply, the remediation values are achieved and the harmless end product is determined.
In a next phase, the source zone around the sewage system will be tackled by means of injections of the proven injection mixture.
The hair cutting plants in Lokeren are an integral part of the cityscape. Symbolized by 3 modern statues of hares on the Lokerse market, the aim is to perpetuate the industrial history of the Durme city. In the 19th century Lokeren was the centre of hat making. This then evolved into the hair cutting industry in the first half of the 20th century. In the hair cutting plants, the rabbit and hare hair was made to felt strong with the help of a mercury solution, after which it could be used to make hats. When this industry collapsed in the 1960s, several contaminated plots were left behind, which still have an impact on the environment to this day.
In the Princess Josephine Charlotte Park there was a need for remediation because of the contamination with mercury in the soil and in the groundwater. Initially, this was a surface remediation, but due to the proximity of the Durme, drainage was necessary in view of the high groundwater level for an excavation in the dry. It was also important that various parts of this recreation area were preserved in their original state.
During the excavation, several cyanide stains were found in addition to mercury, presumably remnants of the former gas factory, on the other side of the street. There were a few zones on the site where the contamination was deeper than initially anticipated, which meant that extra drainage had to be installed. To purify the groundwater, ion resin filters were mobilized in combination with a sand filter and an activated carbon filter. These ion resin filters were able to adsorb both the cyanides and the mercury. Due to the large amount of hanging water, open well drainage was also necessary in addition to strand drainage.
A suction truck was deployed around various trees that had to be preserved to remove the contaminated soil between the existing root structure. This vacuum cleaner has a dust filter, which prevents the emission of soil particles. To avoid contact with soil particles in the excavation zone itself, the park was closed on all sides. The personnel present at the site were required to wear a P3 mask in combination with a Tyvek® disposable coverall.
After the remediation work was completed, everything was replenished and the site was restored to its original state, just in time for the park's annual Theatre Festival.
In the past (2nd half of the 19th - 1st half of the 20th century) a gas factory with 3 above-ground gas holders was located near the playground of the VTI in Lokeren. During the production of the gas, which was extracted from coal, harmful waste products such as tar and cyanides were released. These waste materials caused soil and groundwater contamination. Ghent Dredging was commissioned by OVAM to carry out the remediation on this site.
After the demolition of some above-ground elements and the removal of the hard surfaces, both the core zones and the contaminated top layer were excavated on the site. The contaminated soils were transported to our own GSC Rodenhuize in Desteldonk, from where the various approved partial batches were transported to recognized processing centers. In view of the high natural groundwater level, the groundwater was locally lowered at the core zones. The extracted groundwater was purified and then discharged into the sewage system
The pure product (tar) present in various underground tar pits was judiciously removed and disposed of for processing.
After the excavation, the construction pit was replenished in function of the subsequent use.
The playground was provided with a renewed, disconnected sewerage system, new paving stones and an awning.
Thanks to these soil remediation works, the risks present on the site were removed and a liveable, healthy and renewed neighborhood was created. After the remediation, a new school building will be built on the site.
After several analyses, the contaminated soil was found to give off mercury vapours. In order to carry out this remediation in a smooth and safe manner, both for our staff and local residents, the following additional safety measures were taken:
The contaminated soil could be excavated in two different zones, to a depth of 0.7 and 2.5 metres below ground level, respectively. When the remediation started around July 2019, the groundwater was below 2.5 metres, so no drainage was needed to pump up the groundwater.
The excavation near the school buildings could be carried out by excavating in slices. Both the primary and secondary segments were filled with stabilized sand. The rest of the site could be excavated under a safe slope of 45°. In addition, many remnants of old foundations and much rubble were present in the subsoil. The water and gas connection entered the administrative building at the front and was connected to the sports hall at the back of the site. Since this water and gas pipe crossed the area to be excavated, this water and gas pipe had to be disconnected so that it could be used again after the excavation. The existing sewage system also crossed the excavation zone. This part of the sewerage system was suppressed, after which it could be repaired and split into a separate sewerage system.
After the remediation works were completed, the site could be finished. Different final intended uses of the site provide a varied landscape: paving, both the water-passing and the standard variant, green zone and gravel valleys.
To stimulate the biological degradation of a contamination with chlorinated solvents, we carried out injections on behalf of OVAM at a site in Mechelen, which is currently used as a paintball site. Some of the injections took place along the adjacent towpath of the Dyle.
At the site, 25 injections were carried out in a grid to a depth of 7 metres. Protamylasse solution (fertilizer) was injected into the sandy soil using the direct push technique.
When injecting, the impact on the terrain is limited.
In order to be able to carry out the excavation in the dry, the groundwater was lowered. The pumped-up groundwater was purified by a mobile water purification unit before being discharged into the sewage system.
A new retaining wall was placed in front of the inclined plane and the site was re-landscaped with green zones and asphalt.
Due to the good cooperation between OVAM, the school and the flexibility of Ghent Dredging, these works could be carried out during the school holidays according to a tight schedule and phasing. As a result, the safety and functioning of the school was jeopardized as little as possible. The site was upgraded by carrying out soil remediation, which again offers possibilities for the future of the school.
Mechelen large pond is a project that has been in progress in various phases for about 10 years. In the previous phases, 2 locks had already been completed and a coffer dam built. Also the facilities for the established water ski club, such as the construction of new jetties, had already been completed. The 9th and final phase of this project includes the construction of a compartmentalisation dike, which divides the large pond into 2 closed compartments, and the lowering of the overflow dike located next to the Dijle, which is part of the construction of the Sigma Plan. The large pond was originally a sand extraction pit for the construction of the highway next to it. This enormous pond is now being transformed into a buffer basin and a nature and recreation area.
The construction of the compartmentalisation dike will create 2 separate flood areas. The northern part is being designed as a flood control area with a controlled reduced tide (GOG-GGG). This area receives a volume of water every tide via an inlet lock, creating an estuarine natural area. The southern recreational part, where the water ski club is located, will be set up as a flood control area which will only be flooded in times of extremely high water. The flood plains will serve as a buffer basin during storm tides to protect the environment from flooding.
The underwater slopes of the compartmentalisation dike are protected by geotextile with cobble stones. These protect the dike against erosion due to water flow and wave action.
The works to be carried out by Ghent Dredging mainly consisted of a large amount of earthmoving. The overflow dikes were covered with asphalt in-situ and asphalt mats prefabricated on site. This OSA (open stone asphalt) provides protection against washing out of the dike in the event of flooding.
As part of the realignment of the Trith-Mortange section of the River Scheldt, Ghent Dredging was awarded and subsequently completed this contract for its client Voies Navigables De France (VNF) to create a 500m-long embankment. The ecological construction consisted of approx. 6,500m³ to create a wetland-like riverbank and the construction of 3 lagoons to encourage wildlife in a semi-aquatic environment.
Additional work consisted of submerging tree-stumps, the construction of a meadow and reseeding the embankment.
A rustic meadow was then sown along the bank.
In the context of the Sigma plan, the National Water Authorities (W&Z) is constructing a range of flood planes along the tidal rivers to reduce the risk of flooding in urban areas. The Zennegat contract at Battel is part of the Sigma plan. The area involved is known as the mouth of the River Dijle, where the Rivers Dijle, Zenne and Nete merge into the River Rupel. The scope of the contract is to create a 150-acre flood plane to reduce the tidal impact.
As a result, the River Dijle will get a bigger area with controlled flooding capacity, resulting in a reduced risk of flooding in both the adjacent area and the wider region. At the same time, rare wetlands, so characteristic for this area, will flourish again.
As of now, at each flood tide a reduced quantity of water from the River Dijle will now flow through the lock at the Zennegat. At ebb tide, the lock will discharge the water back into the river. The artificial tidal movements will slowly create gullies, creeks and wetlands, an ideal habitat for rare species. Moreover, fish can continue to swim through the lock.
During extreme weather conditions, the area will be allowed to flood in a controlled manner. When water levels rise to a set level, the water will flow into the Zennegat, using the overflow dike.
This overflow is the former Dijle dike, lowered and reinforced to allow water to flow across.
Because the Zennegat is able to store a large quantity of water, urban area will be safeguarded from flooding.
It is predicted that the Zennegat storage area will be used several times per year. After each flooding, the lock will discharge the water into the River Dijle in a controlled manner.
At Sequedin the River Deule has been widened. Just before reaching the Port of Lille, the canal narrows due to disused power station.
Along this stretch a new quay wall has been constructed. Our contract involved the removal of surplus soil surrounding this new quay wall and incorporating either end of the quay wall into the existing riverbank.
The main problem consisted of the removal of the old foundations of the power plant and two concrete abutments of a former pedestrian bridge. About 5,000m³ of concrete were s been demolished.
After removal of the concrete foundation, earth works started in earnest, including the construction of the river banks and its protection.
After dry-removal of the soil, the old retaining wall was removed. Its steel sheet piles were taken out using a pontoon-mounted telescopic crane.
Finally, the remainder of the soil was dredged and disposed of using barges. In all 70,000m³ of soil was removed.
To store this soil, an old fill area at the village of Emmerin was re-opened. Its bunds were raised using dry excavated material from Sequedin as well as locally found soil. In the final stage of the project, dredged material from Sequedin was dumped into this area.
At Zele, Ghent Dredging raised the Scheldebroek Controlled Flooding Zone´s surrounding bunds and reinforced them up to Sigma Standards (Sigma-Scheme is the Flemish Flood Prevention Scheme).
Also included in the contract were road works, the creation of access to surrounding fields, ponds, planting of shrubs. The required quantity of sand (80,000 m³) was dredged using our 85-tonne backhoe dredger at St. Amands which discharged it into elevator barges. The sand was later spoiled by using our barge unloading suction dredger.
At Ghent, a temporary dam around Gravensteen Castle was removed. The dam had been put in place to allow the restoration of the outer walls of the Castle.
The dam has been excavated back to the original level. The adjacent park area has been reinstated with topsoil and reseeded.
The result: after many years the Gravensteen Castle is once again a moated castle.
Hamme-Lippenbroek has been transformed into the world´s first Controled Reduced Tidal Zone. The system has been developped by the Flemish Authority to answer today´s challenges to prevent large-scale flooding in the River Scheldt catchment area. The purpose of this 25-acre overflow area is to reduce extreme high water levels in the River Scheldt during excessive flood tides by allowing this area’s lowered river embankment to be over-topped. As soon as river water levels drop and return to normal, the zone will drain itself. At the same time, this allows the Environmental Agency to create valuable biotopes. This second objective was to create a nature reserve. To achieve this, a lock has been incorporated in the existing river bank, which allows the creation of an artificial tidal zone with muddy wetlands.
Hamme-Lippenbroek proves both objectives are viable.
Ghent Dredging was involved in the construction of the ring-shaped bund for which over 160,000m³ of soil has been moved as well as the construction of the sheet-piled foundation concrete lock.
Ever since the late 1990s, the Zwin nature reserve has suffering from considerable silting up and, as a result, not enough seawater is reaching the inner part of the reserve. For this reason the existing artificial bird islands are losing their attraction for birds to settle. The bird population on and around the areas has decreased over the years.
As part of the European ZTAR-nature project, Section Nature and Forest awarded Ghent Dredging a contract to create a number of new bird islands to offer new opportunities for a number of bird species. In particular the seagull, the common tern and the avocet.
Included in the contract was the construction of a weir/bridge. The purpose of its construction is to make sure sufficient water will be available around the islands at all times and allowing access to the public.
To make sure the incoming seawater would stay within the nature reserve, some of the existing channels have been filled up, while other channels have been dug, ensuring a perfectly regulated water management of this nature reserve.
Under another contract, about 20 acres in the north-easterly part of the Zwin area, close to the estuary of the main Zwin channel, have been lowered by removing the nutrient-rich top layer. Its purpose is the recreation of the original flora. The area has been rejuvenated through lowering. The resulting mud areas should evolve into an area rich in a variety of species such as samphire and statice, the locally well-known "Zwinneblomme".
The construction of the new Houtdok Park is part of the Old Dock Urban Renewal Project, located around the Houtdok, the Achterdok and the Handelsdok. Where the port industry used to be, a brand new district is now being erected. After Ghent Dredging had previously carried out the project at Schipperskaai, the City of Ghent has now entrusted us with the construction of the Houtdok Park (Captain Zeppos Park).
At the start of the works, most of the site was paved. All this had to be broken up, including the existing foundations of the old harbour sheds.
Once the site was fully prepared for construction, it was possible to start building the future 'Captain Zeppos Park’. Many different disciplines came together in this project, which is precisely the strength of Ghent Dredging.
The project consisted of the construction of walking and cycling paths in washed concrete, the renovation of an old boat lift, the local repair of the 19th-century masonry arches, the construction of a beach with a jetty, the realization of a sports park, the installation of various street furniture and a steel access construction to the old harbour crane.
In the spring of 2020, the residents of the Muide and the “Old Docks” were given 30,000 m² of extra green space for walking, resting, sports and playing.
Since the access to the industrial zone near the Brussels ring road on the left bank of the canal, between the Bergensesteenweg (N6) and the canal, is not optimal, the Drie Fonteinenbrug is being built. This new bridge will relieve traffic on the N6 and in the residential areas.
The aim of this sub-project was the realization of the embankments and the construction of the access road on the left bank of the canal to Charleroi in Sint-Pieters-Leeuw.
Before the planned elevations could be implemented, the sites had to be prepared for construction, in particular the removal of a historic embankment with aerated concrete. In total, more than 22,500 tons of Ytong were excavated and removed.
In view of the non-supportive subsoil present, a pre-consolidation had to be carried out so that the necessary settlements could manifest themselves. In order to realize this consolidation, over-heights of up to 1 m were created. To carry out these earthworks, a total of 34,000 m³ of soil was processed, of which 30,000 m³ was supplied partly over water.
Only after consolidation of the subsoil could the construction of the road, consisting of a roadway and separate bicycle path, be carried out. Together with these works, sewers and buffer canals also had to be realised.
The coming years will see a huge make-over at the north of the city of Ghent, including the old quarter "Old Docks", once the centre of the industrial history of the city. It will be given a new designated use due to the construction of new projects and neighbourhoods.
The first project in this area was the reconstruction of the Schipperskaai. Using the Batavia bridge, this will provide access to the city centre and will be the heart of the new neighbourhood, with the concrete plant and the harbour cranes as its eye-catchers.
Prior to the reconstruction, the polluted soil had to be removed. This polluted soil resulted from the use of the area when timber sleepers were treated with creosote.
After the sanitation of the area, a new sewage system was built, serving as the drainage system for the building yet to be realized along Schipperskaai, including a pipe-into-pipe renovation of some existing concrete drainage pipes to ensure the drainage to the Handelsdok.
The final part of the renovation was the Schipperskaai itself. The main feature is the old railway line, reused to preserve the old industrial look. These are held in place using in-situ concrete sleepers.
Roads consist of cobbles, cast in concrete. The area is designed as a pedestrian promenade. Smooth-finished retaining walls will serve as seats for those sauntering along the waterside and concrete steps will give access to the buildings yet to be erected.
The icing on the cake are two additional harbour cranes, erected along the existing one.
In Ostend, the 800-metre long "Vismijnlaan" was completely redeveloped. The project included the construction of sewerage (from 2 to 4 m deep, diameter 400 to 800), 30,000 m² of asphalt, a 30,000 litre KWS separator, etc. Also, 2 roundabouts and a bicycle path were constructed. Ghent Dredging took care of all works ranging from sewerage to complete finishing of roads and parking.
Ghent Dredging has been involved in the construction of the Plassendale 1 Industrial Estate.
The 6-year contract is regarded as being the perfect example of the successful, mixed deployment of all our in-house experience.
Road works include the estate´s access road as well as Greenbridge´s roads and roundabout. Greenbridge is the University of Ghent´s Science Park.
Earth works comprised the construction of foundations for buildings, the foundations for the Ostend to Plassendale rail line and the excavation of its inland dock, of which 200,000m³ has been excavated, while the remaining 100,000m³ has been dredged using our cutter suction dredger.
The cycle path between Bovenschelde and Spierekanaal and the new jetty on the Spierekanaal were constructed by Ghent Dredging.
This project connects the existing tow paths along the Spierekanaal and the Upper Scheldt towards Helkijn and Warcoing. The cycle path was constructed using different types of pavement, depending on anticipated future use. In total, 5 km of cycle paths were constructed, 800 m of cycle paths were repaired and a new jetty was built for pleasure craft.
Via the Roubaix Canal and the Marque, the Spierekanaal connects the Scheldt with the Deûle for pleasure craft. More information about these works can be found at the References Dredging Works (Roubaix Canal and Spierekanaal).
The zone "De Blokken" is a former production site of the company Bekaert. The site was purchased by Intermunicipal Leiedal and redeveloped as a business park. Two large Bekaert production halls were located on the site, which have largely been demolished. Part of the shed along the old railway bed has been preserved and can be reused for a new business activity.
A new access road was constructed to divide the site into industrial plots. The necessary buffer basins were constructed along the Keibeek that adjoins the site. During the redevelopment, this stream valley was upgraded to a pleasant park environment and the necessary bicycle and pedestrian connections were provided. All these works were carried out by Ghent Dredging.
From time to time Ghent Dredging carries out geotechnical site investigations in joint-venture with specialized consultants.
On the River Meuse we collected bore-hole information for our client AIDE in joint-venture with Geolab. Together with MT's geotechnical department we did the same for BAM (holding company responsable for the new River Scheldt crossing) at the Port of Antwerp's Straatsburgdock.
Samples were taken at regional (polluted) silt-storage site Callemansputte at Ghent, also in joint-venture with MT"s geotechnical department. We also took samples on the River Scheldt, with a tidal difference of some metres.
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