The Oranje Locks are a group of locks and other water management facilities just east of Amsterdam.
Characteristics The Oranje Locks are located in the IJ Dijk, a dam which cuts through the IJ just east of Amsterdam. This dam runs from the village of Schellingwoude in the north to the eastern side of the Amsterdam–Rhine Canal in the south. The dam closes off the Inner IJ, just north of Amsterdam, from the Outer IJ, and hence from the IJsselmeer / Markermeer.
The Oranje Locks consists of the original locks called Oranje Locks and the recent Prins Willem-Alexander Lock. They regulate the water level in the North Sea Canal, and prevent brackish water from reaching the IJmeer. As it is part of the waterways of national interest, the locks are managed by Rijkswaterstaat.
The original Oranje Locks consist of three locks that are now used for recreational vessels and small commercial ships. These are traditional locks with gates that are kept closed by the water pressure. The largest has a lock chamber of 90 m by 17.50 m. The two on its sides have lock chambers of 67 m by 14 m. The two locks on the sides form a pure twin lock, i.e. two locks of the same size in the same location with the purpose of increasing the speed with which ships are serviced.
The biggest lock at the location is the Prins Willem-Alexander Lock opened in 1995. This is a lock of an innovative type, with sliding gates which use a 'hydro foot'. The hydro foot is an alternative to the wheels which normally support a sliding gate. The idea is that a 0.1 mm layer of water in the two hydro feet supports the 50 ton lock door. The lock chamber of Prins Willem-Alexander Lock is 200 m by 24 m.
Every year about 120,000 vessels use the locks. Pedestrians and cyclists can cross the IJ over the dam and locks. The dam also has two fish ladders. Just north of the locks are the first stone houses of Schellingwoude. The 23 houses were built for the engineer, the lock master, the maintenance official, and a number of workers. There is also a former post and telegraph office for skippers dating from 1909.
Context and plans for closing the IJ
The connection of Amsterdam to the sea silts up (1600-1830) In the seventeenth and eighteenth century the approaches to the harbor of Amsterdam became ever shallower. This was blamed on sediment getting pushed into the Zuiderzee from the north. Most of it collected near Pampus, a shoal which became ever higher. In order to circumvent the shallows near Pampus, the Noordhollandsch Kanaal was constructed from 1820 to 1825. This ship canal connected Amsterdam to the harbor of Nieuwediep at Den Helder. The canal created an inland waterway by which ocean-going ships could reach the IJ. For quite some time, this provided Amsterdam with a suitable connection to the sea.
The Noordhollandsch Kanaal did nothing to deepen the harbor of Amsterdam. Plans to solve this by dredging were not successful. This is how the idea to construct a dam and locks in the IJ, just east of Amsterdam came up. From 1826 to 1828 the government worked on the realization of the Goudriaan Canal. This was a canal which would circumvent the Pampus shallows by digging a canal from the IJ through Waterland and Marken Island. In order to prevent the area south of the canal from silting up, a dam would be constructed through the IJ just east of the entrance of the canal. The execution of this plan was opposed by Amsterdam, because of this closure of the IJ. When Amsterdam accepted to construct the Westerdok and Oosterdok wet docks in order to get a deep water port, the Goudriaan plan was cancelled. This way Amsterdam also again got a suitable harbor for some time.
Plans for the North Sea Canal
After the opening of the Noordhollandsch Kanaal, the size of ocean-going ships continued to increase. Slowly the Noordhollandsch Kanaal became unsuitable for Amsterdam. In 1852 the municipality of Amsterdam ordered an investigation into the possibilities for constructing a canal from Amsterdam to the west, the later North Sea Canal. At first nothing came of the plans to construct the canal. This changed when the Amsterdam Municipality offered 3,000,000 guilders in support of the canal in March 1860. In October 1860 a law for the North Sea Canal was proposed. It contained a design for a canal which would end near Willem I Lock, at the start of the Noordhollandsch Kanaal.
The first serious plan for the North Sea Canal was rather straightforward. It was projected north of the IJ and had two locks, one at the sea side, and one at the IJ near Amsterdam. This way, the level of the canal could be maintained. The disadvantage of this solution was that ocean-going ships would have to pass two locks to get before Amsterdam. The general mood in Amsterdam was for supporting this plan, for fear of not getting a canal at all. However, when the details were discussed, it was noted that the reasons to resist the dam and locks in the eastern IJ in 1828, were no longer valid.
Plans to dam of the IJ In August 1861, the municipality of Amsterdam announced to the government that it wished to close of the IJ east of Amsterdam. This idea would become the key of the North Sea canal as it was constructed. With other concessions, this led to the law of July 1862, which proposed to sponsor the construction of the North Sea Canal by a private company. In December 1862 and January 1863 both chambers of the parliament finally gave their consent to this plan.
In the first versions of the final plan, the IJ was closed of from the Zuiderzee by a dam which stretched from the polder IJdoorn in the north over the Pampus shallows to a battery position in the Diemer Buitenpolder in the south. (Dutch sources rather consistently referred to a , and not to a . It was generally called till the 1932 Afsluitdijk was built.) This planned location seems in line with a location from the Goudriaan Canal plan. This dam would be the first work to be completed. Amsterdam urged its completion before any other works in the IJ, in order to prevent further silting up of its harbor during the construction of the canal. Somewhat later a commission ruled that a 1 km wide stretch of this dam would have to be left open until its lock, sluices and their steam engine had been commissioned.
The Pampus Dam of the plan presented in July 1862, contained one lock. This lock would be 18 m wide with a depth of 4.50 m below Amsterdam Ordnance Datum (AOD). It would have three pairs of gates facing the Zuiderzee, and two pairs facing the IJ. Before the lock, 300 ships would have to be able to more at quays in the Zuiderzee. There would also be sluices in this dam, which would keep the canal at the desired level with assistance of a steam engine. (In Dutch, can mean a lock or a sluice, and so the Dutch could refer to both by using the plural , but in this case it meant one lock, plus one or more sluices.) The length of the Pampus dam would be 4.5 km.
Final location of the Oranje Locks
In March 1864 a request from the skippers of vessels on the Zuiderzee was sent to the government. They opposed the location of the dike from near the lighthouse on the IJ at Vuurtoreneiland towards Diemer Buitenpolder. Instead, they wished that the dike would be constructed as close as possible to Amsterdam. They favored a location between Paardehoek (north east angle of the dam around the Oosterdok near Zeeburg) and the city. By October 1865 the government allowed the constructor of the North Sea Canal to choose between closing the IJ at Pampus or at Paardehoek. By November 1865 the changed plan referred to the lock and sluices at Paardenhoek.
The changed plan for closing off the IJ still contained only one lock, and multiple sluices. The projected long and wide lock did not cater to the interests of the skippers on the Zuiderzee. Their small but very numerous vessels could be serviced by one large lock, but they foresaw long waiting hours. Instead they thought that three locks were required, even if they were smaller. At about this time the locks got named (Zuiderzee Locks). The construction of the North Sea Canal was led by Justus Dirks. The part of the Oranje Locks was entrusted to G.J. van Gendt Jr.
Construction of the Oranje Locks
Construction of the dam
The dam through the IJ was 45 m wide at the base, and 4 m at the top. The top was 3.5 m above AOD. The IJ side of the dam was steeper than the Zuiderzee side. The slopes, berm and top of the dam were faced with a layer of at least 1 m of puddle clay. From the top to 0.5 m below AOD temporary fascines loaded with stones protected the dam against waves on both sides. After closure of the dam, this was replaced by stone pitching till the top on the Zuiderzee side, and till the berm on the IJ-side. The pitching was at least 0.30 m thick, with a layer of 0.20 m of broken bricks below. The dam was constructed by first putting a thick mattress of interwoven fascines () over the whole breadth of the dam. The first of these was called , because it reposed on the bottom or ground. In two places these grondstukken would later break, causing considerable sinkage.
By October 1866 the dam from the Waterland dike till the future location of the locks in the 'pit of Schellingwoude' and a part of south of it was under construction. About a 100 meters of it had already reached a height of 1 m above AOD. During 1867 work on the dike steadily progressed.
Construction of the Cofferdam of Schellingwoude The Cofferdam of Schellingwoude was constructed in the area where the locks, the pumping station and a sluice were planned. Here, the water was 3 m deep. The cofferdam later proved to be one of the most difficult aspects of the plan. The cofferdam was originally a circle of 160 m diameter on the inside, surrounded by two concentric rows of closely aligned sheet piles with a space in between the circles of . The space in between the piles was filled up with puddle clay. On the inside a mound of sand was to act as a counter weight to the water pressure. The pit would be made empty so the foundations could be constructed on dry ground. When empty, the pit would face the massive pressure from the water on the outside.
On 9 July 1866 the first pile was driven. It became part of a dolphin, to which the piles of the exterior ring were set. A correct measurement of the distance of 80+ m was crucial to attain the perfect circle which would give maximum strength to the coffer dam, but this led to much trouble. A hempen rope stretched unevenly, floating rods could not be kept in place, and finally an iron wire rope kept strained by weight was used.
By October 1866 a thousand piles had been driven into the ground to form the cofferdam. The idea was to finish it before winter set in. Works on the foundations for the pumping station, sluice and locks could then start in spring. However, the final design for the lock and sluices had not yet been sent in for government approval. By February 1867 100-120 piles still had to be driven in.
Cofferdam troubles and the foundations of the locks On 11 May 1868 the pit for the foundations was made dry. That month 3,000 m3 of ground was removed from the pit. In June another 3,500 m3 of ground was removed, and part of the digging reached a level of 6 m below AOD. In July another 10,500 m3 was removed. On 19 July the first pile for the locks was driven into the ground.
On 29 August some water came up inside the pit near the pumps. The contractor then decided to open the sluices of the pit so it would be filled with water and no further damage would occur. Next, a new screen of closely fitting piles was driven 5 m inside the ring to secure the bad place. 3,600 m3 of sand was then used to fill up this place. The pumps were relocated to a position outside the cofferdam. After these repairs the pit was made dry again, and on 25 September pile driving was resumed. A total of 587 piles would be driven till a real disaster occurred.