Dredging of waterways

Do you have land available for a pasture depot?

The water board is currently actively seeking landowners near the waterways to be dredged who are willing to make their land available for the establishment of a meadow dredging depot. We are looking for approximately 20 hectares of available land in the region.

More information about the how and what, the locations, and any compensation:

• What is a pasture depot?

Why we clean up sludge from time to time

There are a number of reasons why we clean up sludge from time to time:

• The thicker the layer of silt, the less space there is for water. This can hinder the inflow and outflow of water. This has a negative impact on agriculture and other water-dependent sectors. 
• This increases the risk of flooding. Boats also have less space to navigate. 
• All kinds of substances remain trapped in dredged material. These sometimes include substances that are harmful to water quality.
• Silt contains plant debris that is decomposing. This process consumes a lot of oxygen. As a result, living plants and fish have less oxygen available.

How do we dredge?

The vast majority of the dredged material is deposited on the adjacent plot using a crane. The crane is positioned on the bank next to the water. The area where the crane is positioned and the dredged material is deposited must be free of fruit, crops, and materials, for example. We do not dredge close to the bank of the waterway and do not remove solid ground. This ensures that the bank remains stable.

Where dredging with a crane is not possible, we use other methods. For example, we use a boat with a push blade. The dredged material is then pushed to a location where a crane on the shore deposits it on the plot or loads it into dump trucks for removal. When the work is complete, we restore the site and the surrounding area to their original condition. We also flush the culverts and roads clean.

Naturally, flora and fauna are taken into account by, for example, placing flags on breeding sites and mowing in good time so that birds do not breed where dredging is to take place. This is done in consultation with a certified ecologist.

Who does what?

Who actually dredges which stretch of water? Agreements have been made about this:

• Do you own land along a ditch? Then you are responsible for ensuring that there is not too much silt at the bottom of the ditch. We check this every year during the so-called ditch inspection.
• The national government, the province, or the water board ensures that dredging is carried out in waterways. Waterways are rivers and canals where boats are allowed to sail. Municipalities dredge ponds and urban waterways.
• The water board clears the dredged material from canals and ditches that are important for the drainage and supply of water.

Preparation and implementation of nationwide dredging 2025–2026

The Hunsingo Canal, Hoornsevaart, and Molenrijgstermaar waterways require dredging. In preparation for this dredging work, we are in discussions with the municipality of Het Hogeland, among others, to collaborate on our dredging tasks wherever possible.

Before the actual dredging work can begin, the water board will ensure that:

• Surveying the waterbed (measuring the amount of silt in the watercourse)
• Coordinating the work with landowners
• Inventorying and inspecting cables and pipes
• Inventory of bank protection measures
• Conducting local waterbed surveys
• Conducting a flora and fauna survey
• Drawing up specifications
• Initiating the tendering and contracting procedure
• Searching for suitable locations for pasture depots 

Dredged material disposal

In rural areas, dredged material is deposited on the shore where possible. Adjacent landowners are informed of this in good time and are obliged to accept the dredged material. In urban areas, there is often no space available to process the dredged material on the shore, in which case it is transported to a processing site. 

Processing location GSP - Groningen Sea Ports

The water board has made agreements with Groningen Sea Ports to construct a processing site near Delfzijl. The GSP site in Farmsum needs to be raised for future development. By using dredged material as fill after it has dried, there is no need to bring in sand to raise the site. This means that the dredged material can be put to good use.
 

Projects

In practice, a distinction is made between dredging the narrower main waterways by our own service (regular dredging) and dredging the wider lakes and canals (projects) by a market party. The following lakes and canals will be dredged:

Year 2025

• Delfzijl / Appingedam (The second part will be carried out in November, December 2025, and January 2026)
• De Held / Gravenburg (Implementation period October to December 2025)

National dredging work is also set to begin

• Part of the Boterdiep (between Bedum and Zuidwolde)
  Implementation period in November, December 2025, and January 2026.

For the year 2026

National dredging work

• Hunsingo Canal
• Loan boat
• Hoorn Canal
• Mill Row Canal

What do we do with dredged material?

We usually determine the quality of the dredged material using the waterbed quality map. In specific situations, an engineering firm conducts a waterbed investigation on behalf of the water board. More information:Application of soil, dredged material, and building materials

Once the quality of the dredged material is known, we can do two things with it:

• If there are harmful substances in the dredged material, we remove it. An example: A sewer overflow is a type of valve in the sewer system. When the sewer is too full, it discharges dirty water into ditches via this valve. The sludge at this location may be contaminated and will then be removed. Sometimes the sludge is only slightly contaminated and can still be processed elsewhere (e.g., in a dike).
• Does it contain any harmful substances? If not, we scoop up the dredged material on the bank along the water. This dredged material can be used for all sorts of things, such as filling in a depression in a plot of land, processing the soil behind newly installed revetment, building new dams, or, in larger quantities, raising quays or widening verges.

Obligation to accept

Owners of land adjacent to main waterways are subject to a reception obligation. This means that they are obliged to accept the dredged material on their land when maintenance is carried out by the water board. If dredged material is processed on your land, you will receive compensation from the water board. 

Compensation for dredging

From July 2020, there will be a new compensation scheme for dredging. Owners and users of land who have to process the dredged material themselves are entitled to compensation. This compensation is a contribution towards the costs, based on the costs that the water board would incur for spreading the dredged material. An amount will be paid based on the number of cubic meters of dried dredged material received on the land. Owners will receive a letter from us when dredging material is to be received. The letter will always include the contact details of the water board representative who can answer any questions and arrange the compensation.

Processing fees

The processing fees are indexed annually based on the Consumer Price Index.
In 2025, the water board will reimburse €2.19 per m3 for up to 4 m3 of dried sludge per linear meter. 
If the amount of dried sludge exceeds 4 m3 per linear meter, the compensation for the costs will be €2.96 per m3.

• Compensation scheme for dredging (rate set by the General Board on October 25, 2022).pdf

Processing the dredged material on the plot

Virtually all dredged material in our area is suitable for use on agricultural land. In some cases, it is necessary to take brown rot, PFAS, or chloride into account. 

Brown rot

Brown rot survives in sludge for approximately one month. Please note that the brown rot bacterium can survive longer in the bittersweet plants present in the sludge. Prevent the risk of contamination by spreading the sludge thinly and not growing any host plants on it for one year (especially potatoes and rocket leaves).

PFAS

There is very little PFAS in the waterbed in Groningen and Drenthe. In 2019, the waterbed in the Noorderzijlvest area and our neighboring water board Hunze en Aa’s was examined at fifty locations. That examination showed that the concentration of PFAS remains well below the standards.

Chloride

In the ditches, ponds, and canals in the northern sea clay area, the dredged material can sometimes be salty due to salinization. When the dredged material is incorporated in thin layers into or onto the topsoil or arable soil, the effects of salinization will be limited. It is important to note that salinization caused by the spreading of salty dredged material is only temporary, as salt is easily washed out by precipitation. 
 

Document

• Dredging Program 2021-2027.pdf
• Map of dredging program 2021-2027.pdf
  The map provides an overview of the drainage channels that the water board will dredge in the period from 2021 to 2027.

If for any reason you are unable to read the document or if you have any questions regarding the document, please send an email to info@noorderzijlvest.nl.