Three questions to Bart and Henk about the bottom protection system for Zeesluis IJmuiden
A larger lock means bigger ships and more salt water. The locking process creates large volumes of fresh or salt water flowing into or out of the lock and water turbulence may scour out holes near the inner and outer lock heads, undermining them.
Special bottom protection layers are therefore applied at the inner and outer lock heads. Bart Broekman and Henk Vink of Combinatie BaggerIJ are in charge of the preparation and the application of the bottom protection layers. In this article they will answer three questions about bottom protection.
Why should the bottom near the lock heads be protected?
The locking process creates large volumes of fresh or salt water flowing into or out of the lock which may scour out holes near the inner and outer lock heads, undermining them. In order to reduce this effect, the bottom at the entrances of the lock near the inner lock head (canal side) and the outer lock head (seaward side) will receive extra protection layers. Also the area next to the outer approach wall up to the guard wall will receive a special protection layer. Without bottom protection layers along the lock walls, the scouring action of turbulent water could cause unwanted sand transport along these walls. This could have consequences for shipping traffic, as sand transport could cause changes in water depth in or near the lock. By applying bottom protection layers, we prevent this from happening. Extra attention must be paid to the connection of the protection layers to the lock walls.”
What does a bottom protection layer consist of?
“Our bottom protection method consists of applying two layers of material. The first layer of the bottom protection system is made of bundles of willow connected to a filter cloth. The bundles are tied together crosswise by hand in sections measuring 1 metre by 1 metre. The willow branches give strength to the filter cloth during the transport and the underwater installation and provide a solid first bottom protection layer. The filter cloth also ensures that no sand gets through the bottom protection layers. Due to the light weight of the willow bundles, the filter cloth can easily be lowered and positioned underwater next to the walls and lock heads. This first layer is also called the fascine mattress. The second layer of bottom protection is put on top of the filter cloth and the willow bundles. This second layer consists of rip-rap, loose stone used as ballast.“
How is bottom protection applied?
“In many places, the riprap layer is encased in concrete to ensure that it will not be swept away by water flows due to currents or ships’ propeller movements (wash). Each individual compartment of the fascine mattress on the bottom is covered by concrete by means of a grab which releases the concrete just above the bottom. We have tested this technique with divers and they have told us that it worked OK. After completion, the divers will carry out random checks to see whether every segment has been covered with enough concrete. To ensure that the sandy soil next to the lock walls will remain in place, the riprap along all the walls will be covered by a so-called colloidal concrete mix. This is a special type of concrete that does not dissolve during the pouring process and is not washed away by water currents. The gravel in this concrete comes from K3Deme, a company based in the port of Amsterdam.'
The bottom protection layers ultimately ensure that the bottom of the lock will continue to remain at the required depth and that the sand will not be swept away by water turbulence in the lock. This type of soil protection is expected to protect the bottom of the lock for more than 100 years.
Working together to train lock and VTS operators
Zeesluis IJmuiden will soon be ready for use. But first, staff will have to master the ins and outs of operating the lock. Mia Dröge is Strategic Advisor to the Harbour Master's Division of Port of Amsterdam. Together with a team, she will ensure that the lock can be operated safely.
This includes the training of the VTS operators and the lock operators who will soon be operating the new lock. Mia sees herself as a connector of the various parties within and outside Port of Amsterdam. She talks about her role and activities.
Port of Amsterdam has assigned a number of public tasks to the Harbour Master's Division. These tasks include the handling of shipping traffic. The Harbour Master's Division will ultimately be the organisation that will use the lock to give ships access to the ports in the North Sea Canal area. It is the Harbour Master's task to handle shipping traffic to and from the lock safely, smoothly and sustainably. Many steps will still have to be taken before that can be realised. Mia explained, “The putting into operational service of the new lock involves a lot of preparations. The process starts with a large amount of paperwork, such as the updating of regulations and the making of working agreements with Rijkswaterstaat, the owner of the lock. For example, we need to draw up a new regulation that controls combined lockages through Zeesluis IJmuiden and the parameters of this regulation must be integrated into Port of Amsterdam's digital system. The system will then inform the customers of the port that the lock exists ‘in digital form’. This enables them to send us the required notifications of their ships’ arrivals or departures and it enables us to make lock reservations for Zeesluis IJmuiden.”
The common interest is paramount
In order to make the best possible use of Zeesluis IJmuiden, Mia works together with many different parties. Relations between organisations are good and levels of engagement have increased over time. Mia added, “We work together with different departments of Rijkswaterstaat, with OpenIJ and with the nautical service providers such as the Pilot Organisation, the IJmuiden linesmen and the towing service. We have consultations every four weeks. During these consultations, we discuss the progress of the work. We have been working together for so long that I also call every week to see how things are going. The lines are very short.” Our cooperation, Mia is happy to say, is very pleasant and we can discuss everything. Mia added, “Despite the physical limitations of working from home, we can easily contact each other. I am not afraid to ask critical questions and raise subjects. Even ‘uncomfortable’ issues can be discussed. I look at the common interest of all parties and the willingness to cooperate and move towards a solution. That is a good basis from which to work.”
Working together for the same goal
The various different parties share the same goal: to put the lock into operation effectively and safely. The lock operators and the VTS operators are being trained to operate the new lock. Mia is busy with this. Mia said, “The process is focussed on the lock operators. They are the ones who will actually open and close the lock. The lock operators receive training through e-learning combined with simulations and training in practice. One of the reasons is that the technology of Zeesluis IJmuiden differs from that of the North Lock. The new sea lock is so large that there is no direct view of the moving parts of the lock (barriers and lock gates, for example) from the Lock Operation Centre. That is why cameras are used, so the lock is actually remotely controlled. The lock operators operate all the locks of the lock complex and Zeesluis IJmuiden will soon be added to their set of tasks. Once all the lock operators have mastered the technology of Zeesluis IJmuiden, the VTS operators and other nautical staff will be trained. Their training, though, is less extensive.
Practising with test scenarios
To make sure that everyone is ready for the lock being put into operational service, exercises will be held with Zeesluis IJmuiden this autumn. This will again be done in cooperation with Rijkswaterstaat and OpenIJ. Mia explained that for these exercises, real ships will be used for the lockage process. Mia added, “We are going to test the entire lock process of Zeesluis IJmuiden together with the lock operators, the pilots, the tugboats and the linesmen. We will do this with ships of various sizes, including ships that are already scheduled to call at one of the ports in the North Sea Canal area. We will ask these ships in advance if they are willing to participate in the lock process tests by passing through Zeesluis IJmuiden. During the test period, the other locks will also be operated of course. An increased number of staff will therefore be on duty then. The test period is the final test for all cooperating parties: the builder of the lock (OpenIJ), the owner of the lock (Rijkswaterstaat), the user of the lock (the Harbour Master's Division), and the nautical service providers who assist the ships passing through the lock. Ultimately, Zeesluis IJmuiden must be a safe place for everyone and we must be able to work safely together.’
All the lock gates have been put into position
In March 2021, the last two lock gates on the canal side were successfully installed. The whole operation lasted four days. Edgar Breedveld and Victor Arnolds were involved in this milestone achievement. They directed the positioning process and ensured a good outcome.
They told us about their work and about the positioning process.
Manoeuvring the lock gates into position
The lock gates were towed from Amsterdam to IJmuiden by tugboats. Upon arrival, the lock gates were manoeuvred into the lock and moored there. Victor explained, “After that, the lock gates were installed with the help of winches and tugboats. A winch is a tool with a steel wire that can be used to lift or pull heavy objects. First, the winches were connected to the lock gate. After this, the lock gate was pulled towards the lock gate chamber. With the help of the tugboats, the gate was put into position. When the lock gate was in position, it was sunk by filling the special ballast tanks of the ballast system with water. Once the lock gate was at the correct depth in the inner head gate chamber, the gate itself was connected to the upper and lower wheel carriages.”
One lock gate in the dry dock
Victor explained, “In the same way as the inner gate was brought into the gate chamber, the spare lock gate was positioned into the dry dock next to it. The gate of this dry dock was closed on 13 April. If, in the future, one of the gates requires maintenance, the dry dock can provide easy access to it. The water can be pumped out of the dry dock to allow maintenance work being carried out to the spare gate.”
A tight schedule
The installation of the gates went well. Good preparation proved to be essential. Victor made checklists in advance, which were completed during the final preparations. The whole operation depended on the weather, the personnel and the equipment. Edgar added, “The last days before the scheduled positioning of the gates were hectic. The first series of weather forecasts were not so good, as the wind speeds were above the safety criteria. So we met every day to look at the weather forecast. In the end, the forecasts improved and 72 hours before the operations were programmed, we decided to go ahead with it.” On the day itself, a tight timetable was maintained. Victor explained, “We started the day with a kick-off meeting. In this meeting, we went over everything, such as the weather conditions, personnel involved, available facilities and a thorough check if everyone and everything was complete and ready for action. Then we wished everyone a good day and got to work.”
Points of attention during the positioning of the gates
The main focus for Victor and Edgar was safety for all. Edgar added, “We also had to keep an eye on our own safety because, as the saying goes: ‘out together, home together’.” The operation was successfully completed. Victor explained, “We had planned four days of work for the two lock gates. The first lock gate took 11 hours, the other one 10 hours, so everything went faster than expected. The positioning of the gates into the gate chamber was a daylight operation and the daylight determined when we had to start and stop. Edgar and Victor also had to take the shipping traffic into account. It appeared that ships were hardly affected by the operation. Edgar explained, “During the preliminary stages and the operation itself we kept Port of Amsterdam informed as accurately as possible. We also had applied for all transport permits for the lock gates well in advance. It so happened that there was a lock closure planned for the period of the positioning of the gates, so we had the North Sea Canal almost to ourselves. During the positioning of the gates in the gate chamber, we noticed small water movements due to ships passing the area, but it was not necessary to limit shipping traffic. As the positioning took place mainly in the lock and lock gate chamber itself, any inconvenience by water movements was limited.”
Now that all the lock gates are in position, a new testing period can begin.
The how, what and where of the site layout of Zeesluis IJmuiden
The construction of Zeesluis IJmuiden is almost completed. Now that all the lock gates have been put in position, the area around the new sea lock is being prepared for its future use. During the preparation of the area, everything will be made ready for the opening of the lock.
This includes the asphalting of the public road and cycle paths. Site manager Edwin Komdeur and Chief Planner Dirk Jorna, both of OpenIJ, supervise this process together.
Good cooperation is important
OpenIJ has been working on the design of the site layout for four years. Preparatory work on the area around the lock started at the end of 2018. Dirk gave an explanation, “We have invested more effort in the design over the past few years, so that we had time enough for research, answering questions and fine-tuning the design. The implementation is expected to be quite a puzzle, because some parts of the lock will be ready sooner than other parts. In addition, construction of the lock is still continuing, so we have to deal with many different parties.” Dirk and Edwin try to coordinate the work on the site as well as possible. That is quite a challenge. Edwin explained, “We hold consultations at all levels and try to get everyone on board as much as possible. Every day, we discuss our internal planning with the foremen. And even before that, we coordinate all the work with the planners. They make sure that everyone at work is informed of our activities.”
The preparation of the site will only come into play once the construction of the lock nears completion. Dirk and Edwin will have to face two difficult tasks during this phase. "In the preparation of the site, we face two major challenges, namely the number of different parties carrying out the work and the work planning itself. We work to a tight schedule and are dependent on the weather. Recently, scheduled work during a weekend could not be carried out due to strong winds. So then we had to change the schedule.”
Everything must be included in the design, such as asphalting, cycle paths, road paving, road markings, fences, railings, traffic lights, barriers and navigational markings. Edwin and Dirk and their team ensure that nothing will be forgotten. Edwin explained, “Basically, we follow the design and the construction drawing. But sometimes things may have been forgotten in the design or things turn out differently in practice, certain markings, for example. I discuss such things with Dirk and we try to find a solution. Any changes are corrected and updated in the design so that there will always be a correct version available not only for now but also for future use. Special measures for the Vletterlieden are taken on the platform of the lock. Dirk explained, “The Vletterlieden are the IJmuiden linesmen (or boatmen). They assist ships with mooring and unmooring in the locks and in the port and also provide other marine services. For them, we provide the lock platform with raised edges around the lock wall and apply navigational markings.” The site is mainly laid out with concrete, asphalt and grass.
Site layout of the lock platform
Ships passing through Zeesluis IJmuiden will notice little of the site layout. Something of the layout, such as navigational markings on the lock walls, will be visible on the lock platform itself. Edwin added, “We install navigational markings and stop markings on the lock platform. This way, ships can see how far they have to go before they will be in position for mooring. Pylons for orientation for the ships will be installed at the top and rear ends of the lock. Ships can use the pylons as a visual position and direction guidance system when approaching and entering the lock. In addition, traffic lights and traffic control installations will be installed on the inner and outer lock heads. Traffic lights regulate when ships are allowed to enter or leave the lock.”
Diving operations at Zeesluis IJmuiden
There are also divers at work for the construction of Zeesluis IJmuiden (the new sea lock). They are busy with underwater engineering and construction activities.
Max Schellenbach and Jan-Pieter Steunebrink of Boskalis are responsible for the Boskalis diving department and the execution of the work for OpenIJ. They told us about the work of their divers.
Inspect, repair and supervise
The divers carry out underwater work and assist with a variety of other activities, such as concrete pouring, inspecting and - where necessary - repairing diaphragm walls. Max explained, “Our divers recently inspected over 26,000 m2 of diaphragm walls and touched up joints in the walls.” The divers do not only carry out underwater work, they also assist during important phases in the construction. Jan-Pieter added, “The divers were also present when the lock gates were manoeuvred into position in the lock gate chambers. Approximately 8 to 10 divers were working simultaneously when the lock gates were positioned into the gate chambers. The divers were there to assist the underwater process and were in constant contact with the workers above water to tell them whether or not all was going well."
A wide variety of possible underwater work
Professional diving is a very special career. The work is exciting but also very demanding. Max explained, “Every project is different. Our divers are now diving at the new sea lock at IJmuiden, but may be in Denmark, Norway or even Mexico next month. The possibilities of working as a diver are endless.”
Safety under water
Divers have to take into account all kinds of regulations and legislation with regard to safety under water. Each diving team, for example, consists of at least three divers so that they can take turns. Jan-Pieter agreed and added, “The divers arrive at the pontoon in the morning and then start the day with a cup of coffee and the daily ‘toolbox meeting’. During this safety talk, we discuss what kind of activities can be expected and if there are any specific items of concern. Every dive is different. That is why we make a Last-Minute Risk Analysis before we start. This way, we can understand and keep track of any risks during our working day. I have a lot of contact with the divers during the day. All day long, they keep me fully informed of the diving operations they are carrying out.”
The divers alternate in shifts of three or four divers to work as efficiently as possible. Max explained, “The total diving time a diver can work underwater depends on the working depth. Dive tables indicate how long a diver can safely remain underwater. In the lock, the divers have to dive deeper than usual. Sometimes they dive as deep as 20 metres in the waters outside the lock. Because of this depth, they cannot stay underwater as long as they would otherwise. To extend the diving time, we dive with special air, namely ‘nitrox’. Nitrox is a type of air with more oxygen than in 'normal' compressed air. The divers who are not diving remain on the pontoon. By using special communication devices and by observing the air bubbles, they know approximately the diver’s underwater position. If he needs tools, the divers on the pontoon lower them in the water by means of a rope or by using the crane. On average, each diver works approximately 50 hours a week, based on applicable Labour Legislation.”
It is very dark underwater, so divers always use head torches and cameras. Jan-Pieter explained, “All diving operations can be followed with cameras and sound equipment. If visibility is very poor, due to dredging for example, then everything has to be done by touch. You have to get used to it, but it actually goes very well.” The average water temperature in winter is 5 degrees Celsius. So the divers take special measures to keep warm. Max added, “To keep warm, the divers dive with a special dry suit. No water gets through and the skin stays dry. Divers wear special thermal clothing under this suit. The thickness of the thermal clothing allows them to dress as warmly as they like. In winter we also install a heater on the pontoon and in summer an air conditioner.”
The new sea lock (‘Zeesluis IJmuiden’) - what will happen in March and April 2021?
The contours of Zeesluis IJmuiden are now clearly visible and this means that the final phase of construction has now begun. In the coming months, OpenIJ will continue with the construction of the Loswal (quay) on the Zuidersluiseiland (number 1 in the picture);
The public road across the locks will open for pedestrians, cyclists and mopeds (number 2 in the picture); flood defence north will be tarmacked (number 3 in the picture); the future dyke of flood defence south will be raised to the correct height (number 4 in the picture); protection material will be applied to the bottom of the Nieuwe Zeesluis at the inner and the outer heads (number 5 in the picture); and there will be a lock gate replacement at the outer head of the Noordersluis (North Lock).
Construction of the Loswal (quay) on the Zuidersluiseiland
In the period from September 2020 to June 2021, OpenIJ will be building a new quay on the Zuidersluiseiland, next to the storehouse of the Heida company (number 1 in the picture). The new quay - also to be used as a car landing place for inland ships - will extend the facilities at the Zuidersluiseiland. In the period March and April 2021, work is being carried out to the earth-retaining structure and the embankment protection.
Opening of the public road across the locks
The public road across the IJmuiden lock complex will open on 29 March 2021. The road (number 2 in the picture) will only be open for mopeds, cyclists and pedestrians. The road will remain closed for car traffic until further notice. Cars cannot yet use the public road because there are still a number of construction and maintenance works ongoing at the lock complex. Until the end of 2021, mopeds, cyclists and pedestrians using the public road should therefore take into account extra delays that may occur due to (maintenance) works to the bridges of the Middle Lock (Middensluis) and the use of temporary pumps at the Small Lock (Kleine Sluis). The public road runs across the outer gate of the new sea lock. Testing operations of the outer gate of the new sea lock will be carried out on working days between 19.00 and 24.00 LT. During these periods, the public road will be closed for road for traffic.
Flood defence north
In March, the Middensluisweg near the flood defence north (number 3 in the picture) will be tarmacked. The Middensluisweg is part of the public road across the locks that will be open to mopeds, bicycles and pedestrians as from 29 March 2021. The Middensluisweg will be open to car traffic at a later stage.
Flood defence south
Flood defence south (number 4 in the picture) is where the OpenIJ concrete mixing plant previously stood. The concrete mixing plant has produced more than 300,000 m3 of concrete for the construction of the sea lock. In the coming weeks, the future dyke at this location will be raised to the required height after which OpenIJ will start the construction of the road on top of the dyke.
Protection material to the bottom of the lock at the inner head
On 15, 16 and 17 March (during the closures of the North Lock due to planned maintenance by technical service provider SPIE), OpenIJ will start with the application of protection material to the bottom of the Nieuwe Zeesluis at the inner head. Once the closures of the North Lock have ended, various works will take place in and near the inner and outer approach channels to the North Lock. Shipping traffic will be taken into account during these works. In week numbers 12-14 (22 March to 8 April 2021), OpenIJ will complete the application of protection material at the inner head of the Nieuwe Zeesluis.
Protection material to the bottom of the lock at the outer head and lock gate replacement
During the period from 12 to 14 April 2021, OpenIJ will start the application of protection material to the bottom of the Nieuwe Zeesluis at the outer head (number 5 in the picture). During the closures of the North Lock from 19 to 22 April 2021, OpenIJ will apply protection material to the bottom of the Nieuwe Zeesluis at the outer head. There will be a lock gate replacement of the North Lock on 21 April 2021. The closures of the North Lock have been mentioned in Announcement to Shipping No. 08/2021. In week numbers 17-21 (end of April to end of May 2021), the remaining protection material will be applied at the outer head of the Nieuwe Zeesluis. For this, no further lock closures of the North Lock will be necessary.
Shore power for short sea vessels in the port of Amsterdam
Together we can make the port more sustainable. We are looking at various possibilities to achieve this, in cooperation with our customers and partners. On 8 and 9 February, the first test took place with shore power for short sea vessels at a terminal.
Together we can make the port more sustainable. We are looking at various possibilities to achieve this, in cooperation with our customers and partners. On 8 and 9 February, the first test took place with shore power for short sea vessels at a terminal.
Shipping company Wilson moored their ship Wilson Goole at VCK Logistics' Waterland Terminal. The ship received power via SKOON's battery.
The battery test is another step towards a more sustainable shipping industry. The battery can supply green energy anywhere in Amsterdam and is then filled with local wind energy from Windpark Ruigoord or with energy from biomass from AEB. With this, it is capable of supplying 630 kWh of electricity. This equates to at least twelve hours of shore power. Or two months for a two-person household.
The test shows that it is possible to provide large ships with energy on a regular basis by means of a battery. On locations with a small grid connection, up to 550 kW of peak power can be supplied for longer periods. This has recently been done in cooperation with the Shared Energy Platform (SEP). SEP is an initiative of the Port of Amsterdam to increase the available capacity in the electricity grid.
Adaptations to ships for shore power
It is not easy to connect these large vessels to shore power. This requires certain modifications to the ships. Wilson Eurocarriers sails to Amsterdam on a weekly basis and has already made modifications to 80 of its 126 ships. Robert Bravenboer, Director at Wilson Agency: "We think it is important to make optimal use of the possibilities of shore power. Hopefully this will soon become the standard in all ports. We believe that the sustainability of ports will increase rapidly and we are happy to contribute to this. We are very happy that we were able to do this pilot in Amsterdam'.
Innovation and sustainability at the terminals
VCK is also enthusiastic about the pilot. Peter Loonen, Managing Director of VCK Group: "We value the importance of innovation and sustainability. The battery test is a nice concrete example of this. It's important to us that we continue to invest in the future to ensure that we can provide more of these types of ships with energy in a sustainable way’’.
Making the port even more sustainable
Clean shipping is an important spearhead in the 2021 - 2025 strategy of the Port of Amsterdam. One concrete example of how we are working towards this is the provision of shore power at locations within the ‘ring’ road. This is already possible for inland navigation and river cruise ships. We now want to expand this further for a wide range of vessels at the various terminals.
A name for the new sea lock
In July, the municipality of Velsen and Rijkswaterstaat launched a competition campaign for the naming of the new sea lock at IJmuiden.
Jeroen Verwoort, Alderman of the municipality of Velsen, and Nienke Bagchus, Director of Network Management at Rijkswaterstaat, had made a video in which they called on the Dutch people to send in names for the new sea lock. And with success: The municipality of Velsen received almost 5000 responses! After the submission deadline had passed, the municipality and Rijkswaterstaat started working on a selection of the best names. Jeroen Verwoort explained how this works and when a winner will be chosen.
The alderman is very proud of the fact that the construction of the largest sea lock in the world is taking place in his municipality. Jeroen explained, "We have received a lot of beautiful names. We have also received a number of entries that unfortunately do not meet the conditions. Such as, the 'Irma Lock'. A very nice idea, but regrettably this will not be a good name for the lock. If the lock is to be named after a person, this person must have passed away at least 10 years ago, unless it concerns a member of the royal family."
The selection procedure
Immediately after the closing of the competition a first selection was made. Jeroen said, "The names that did not meet the conditions were filtered out. People who submitted more than one name were also removed from the list. The conditions state that you may only enter once to submit a name. If different persons had submitted identical names, only the person with the first entry would remain on the list."
Almost 5000 entries
The naming committee of the municipality of Velsen will then get to work and choose a top 100 from all the remaining names. After that, the ‘neighbours’, i.e. the people who live in the vicinity of the new sea lock, are allowed to choose a top 5 from these 100 names.
Finally, the Mayor and Aldermen of Velsen will choose the best name for the sea lock from the top 5 this autumn. The winner may be present at the official opening of the sea lock. But first we have to dig through those 5000 entries and see what pretty names have been submitted."
Irma Sluis Lock
A much recurring name was the Irma Sluis Lock, named after the sign language interpreter Irma Sluis ('sluis' is the Dutch word for lock) who played an important role during the press conferences of the Dutch government on the corona crisis.
Unfortunately, that name is not suitable as it does not meet the conditions. Jeroen explained, "If the lock is to be named after a person, this person must have passed away at least 10 years ago.”
The name has to meet several rules and conditions: "The name must be appropriate in an international context. So tongue twisting Dutch consonant combinations such as 'SCH' have to be avoided. The name may not yet have been used for another lock in the Netherlands and, of course, it may not contain any swear words. Of course we get all kinds of names, even less serious ones. That is all part the game and sometimes even funny. The lock will last for the next 100 years, so the name has to be appropriate with that in mind too."
A dredged-out lock chamber
In 11 weeks’ time, 600,000 m3 of sand has been dredged out of the lock chamber by cutter suction dredger 'Biesbosch'. The lock chamber is now at a depth of 19m below NAP. The bottom of the lock will be made of gravel and concrete which, when completed, will give the lock a maximum depth of 18m.
Wessel Mak, Project Manager at Van Oord, is responsible for the dredging of the lock chamber. He has been involved in the construction of the new sea lock since 2014 and gave us an update on the dredging operation.
Wessel Mak told us, "We started our dredging operation of the lock chamber on 29 June. After 11 weeks, the lock chamber was at the required depth. The edges of the lock chamber had been cleaned and the walls sprayed clean by divers. The only remaining item now is the construction of the bottom of the lock."
The whole process
Dredging the lock chamber was an important and extensive process. Wessel explained what the work involved, "We dredged the lock chamber with the cutter suction dredger and a crane pontoon. The cutter suction dredger moved back and forth by means of its anchors. Meanwhile, the cutting head cut loose the sand in the lock chamber. The cutter suction dredger then sucked up the sand. The sand was pumped through pipes, containing a mixture of sand and water, leading from the lock chamber to the spray pontoon. From the spray pontoon, the mixture was pumped into the spray depot situated in the fairway of the outer approach channel to the North Lock. From here, the sand was dredged up again with the trailing suction hopper dredger and then transported to sea. At sea, the sand was dispersed at a designated location."
Dredging is a recurring cycle continuing 24 hours a day. Mak added, "Dredging is always a process that goes on 24/7. That's what dredgers and dredging materials are made for. Dredging continued at night to reduce inconvenience for stakeholders, such as local residents and users of the lock, as much as possible. The crane pontoon dredged the areas directly next to the lock chamber walls. Just like the divers who cleaned the walls, the crews of the crane pontoon also worked 24 hours a day for 5 consecutive days. Dredging activities were planned as much as possible during the day, with extensions into the evening and the night.
The lock chamber has now been dredged to its required depth and the gravel/concrete bottom will be poured in the autumn. Wessel explained, "The lock chamber has to be delivered neatly at its required depth. We dredged up to 19m below NAP. The next step will be the pouring of a layer of 30-50cm of gravel with a layer of underwater concrete on top of that." At around 30,000 m3 this will be one of the largest concrete pours of the new sea lock.
Communication as a challenge
In such a large and complex process, there are many things that had to be taken into account. You are not the only worker at the lock, you see, Wessel explained. He added, "Communication, in particular, was one of our most important challenges. Our work was not limited to the lock chamber, but we were also active at sea to distribute the dredged material. It was important to coordinate this process very accurately. We therefore had daily meetings during which we planned the work ahead. The dredging of such a large lock chamber was really unique!” Wessel, proud of his contribution to the new sea lock, added, "I think you can only build the largest sea lock in the world once in your entire life.
The logistics centre has been relocated
The OpenIJ Logistics Centre is the place where all materials for the construction of the new sea lock are stored. Initially, the centre was located in Amsterdam's Western Port Area, but recently the site has been relocated and the materials have been stored close to the lock complex.
Wouter Sloven is Logistics Manager at OpenIJ and has been involved in the construction of the sea lock for 5 years. He talked to us about the old and new logistics centre.
Wouter explained, "The old Logistics Centre of OpenIJ was located in the Western Port Area of Amsterdam. We rented a small part of the business site there. The lease, however, was going to expire. So we moved and found a place somewhere else. The new site of the Logistics Centre of OpenIJ is now located near the sand depot in Velsen Noord."
Transport by water
The logistics centre is used for storing and transporting goods by water. Wouter explained, "Many materials are heavy and very large. We cannot transport them by road. That's why we need a place where we can store everything with access to transport by water. That is the purpose of our logistics centre. From here we can put the materials on a barge and transport them to the lock complex.
OpenIJ Logistics Centre
Materials are shipped from the logistics centre to the lock complex. Sloven added, "In fact, this is a location for a short interim storage of all materials. The new location has the same function, but is slightly smaller than the location in Amsterdam. There has already been quite some progress with the construction of the sea lock, so we need fewer and fewer materials. The OpenIJ logistics centre is expected to be vacated at the end of March 2021."