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Long-term maintenance contract in Lake IJssel Area

The Lake IJssel Area (IJsselmeergebied) performance contract covers the maintenance and modernisation of bridges and locks in the area around the Afsluitdijk dam, the towns of Enkhuizen and Lelystad, and the lakes around Flevoland province. Arcadis, Croonwolter&dros and Hollandia have joined forces in the SHERPA combination for this large-scale contract for Rijkswaterstaat. As an exclusive partner for the steel and mechanical engineering part of the contract, Hollandia Services takes care of mechanical maintenance and troubleshooting on the structures in the area in question. Aside from that, the contract scope also includes the required revisions of the mechanical engineering and civil engineering aspects of the following structures: Stevin, Lorentz, Krabbersgat, Houtrib, Nijkerker, Roggebot, and IJsseloog.

Stevin Lock

The Stevin Lock is located in the western part of the Afsluitdijk dam near the town of Den Oever. This complex’s primary purpose is to control water levels in Lake IJssel (IJsselmeer) compared to the Wadden Sea. The Stevin Lock is also one of the places where ships can pass through the Afsluitdijk dam. Motorised traffic passes over the lock complex along the A7 motorway.

The complex is made up of three groups of scour sluices that start, viewed from the Den Oever side, just after the lock. The three identical groups each have five sluice boxes that are 12 metres wide, with two sets of six lift-gate towers. The lift-gate towers house the suspension mechanism and machinery for the closing structures. Each sluice box contains a northern and a southern gate between the lift-gate towers on the Wadden Sea side and on the Lake IJssel side respectively. The southern gates or lift gates are the regular water-control structures, while the northern gates are used only in case of a storm. Under normal circumstances, the northern gates are always open. The gates are on vertical rails between the lift-gate towers and raised and lowered by chains with concrete counterweights that run on wheels. These chains, wheels, counterweights, and electric motors are all located in the lift-gate towers.

For shipping traffic, the complex includes a lock that is 120 metres long and 13 metres wide. A pneumatic barrier in the sluice box that is activated every time the lock is used minimises the penetration of salt water from the Wadden Sea into Lake IJssel.

Lorentz Lock

The Lorentz Lock is located in the eastern part of the Afsluitdijk dam, near Kornwerderzand. The Lorentz Lock serves the same purpose as the Stevin Lock at the other end of the dam. The complex is made up of two structures with five sluice boxes each, which discharge water from Lake IJssel into the Wadden Sea. Each of the scour sluices is 12 metres wide and 4 metres deep and can be closed using a set of flood gates on the Lake IJssel side, an outer gate, and an additional inner gate between that. The sluice boxes are made entirely of reinforced concrete with brick sheet piling along the outlet.

A large and a small lock are located to the east of the scour sluices. These locks are used by ships going from the Wadden Sea to Lake IJssel and vice versa. Suited particularly for recreational vessels, the small lock is 67m long and 9m wide. The lock sill is 3.5 metres below the water level. The large lock is 137 metres long, 14 metres wide, and has a sill depth of 3.50 metres. Ships with a navigable depth of up to 3.20 metres are allowed into this lock. To the north of the lock, there are two unique monumental swing bridges with a passage width of 15.75 metres.

Krabbersgat Lock and Naviduct

The Krabbersgat Lock complex in the Houtrib Dike (Houtribdijk) south of Enkhuizen was opened in 1971. The complex is made up of a lock and a scour sluice with two separate orifices. Together, the lock and the scour sluice are the gate between Lake Marken (Markermeer) and Lake IJssel (IJsselmeer) via two bodies of water called Krabbersgat and Hoornsegat. Between 1999 and 2003, the nearby naviduct containing a double lock was built in the Houtrib Dike.

Houtrib Lock

This lock complex is located near the town of Lelystad and part of the navigation route between Amsterdam and Lemmer. The complex was opened in 1975. The locks were renovated over the 2010-2012 period.
The complex is made up of two locks and a scour sluice. The locks are both 190m long and 18m wide. The bridges are approximately 7 metres above the average water level. Every year, around 80,000 ships pass through these locks. The small lock is 67m long, 9m wide, and 3.5m deep, and particularly suited for use by recreational vessels. The locks are operated from a central control tower 24 hours a day.
The scour sluice has six orifices that can be closed using steel lift gates. The total sluice capacity goes up to 630m3 of water per second.

Nijkerker Lock

Dating back to 1962, this lock separates Lake Nuldernauw from Lake Nijkerkernauw. The complex is made up of a lock and a scour sluice. Every year, over 35,000 ships pass through the lock. The N301 provincial road runs across the lock and the scour sluice, crossing a bridge that connects the provinces of Flevoland and Gelderland.

Roggebot Lock

The Roggebot Lock is a lock on the border between the Dutch municipalities of Kampen in Overijssel province and Dronten in Flevoland province. In geographical terms, the lock is located in the municipality of Dronten. The lock connects Lake Dronten to Lake Vossen (Vossemeer).


IJsseloog is a man-made island in the middle of Lake Ketel (Ketelmeer). Shaped like an eye, the island has a large circular hole in the centre that is 45 metres deep and has a diameter of one kilometre. During the digging of this hole in the middle of Lake Ketel, several enormous erratic blocks from the ice age were found, as well as two 25,000-thousand-year old mammoth bones. The hole is encircled by a ten-metre-tall dike. IJsseloog was created as a depository for contaminated silt dug up from the beds of the Netherlands’ various bodies of water. Silt contains toxic substances and metals, such as mercury and zinc, from waste discharged by factories across the Netherlands and Germany. Ships carrying the contaminated silt can moor at IJsseloog’s small port, from where the silt is pumped out of the ships and distributed evenly into the depository by a mobile pipe that stretches across the island.