The Netherlands has a variety of soil types, each with unique properties that influence the presence and movement of groundwater. When applying water management techniques, such as well-point dewatering or ground drilling, the soil type and associated factors must always be taken into account. In this article, we discuss the six most common soil types in the Netherlands and the possibilities and challenges of well-point dewatering in these different soil types.
The main soil types in the Netherlands are sand (48%), loam (light and heavy, 22%), clay (light and heavy, 17%), and peat (9%). A distinction is also made between boggy soils on sand (2%, mainly in the north and east of the country) and loam (2%, mainly in South Limburg).
Sand
Dutch soil consists of approximately 48% sand and is the most permeable soil type. Sand consists of grains between 63 micrometers and 2 millimeters in size. All grains smaller than sand are referred to as silt, and larger grains are called grid. Sandy soil is permeable to water, making wellpoint dewatering relatively simple in this soil type. However, the rapid water movement requires constant drainage management to ensure the construction pit is drained and to prevent subsidence in the surrounding area.
Sandy
The word “loam” comes from the Latin “Sabulum,” meaning “coarse sand” or “gravel sand.” A distinction is made between light and heavy loam and accounts for 22% of Dutch soil. Whether the soil is classified as light or heavy loam depends on the lutum percentage. Lutum is the percentage of clay in the soil, measured in particles smaller than 2 micrometers (µm). A lutum percentage between 8% and 17.5% is considered light loam, and a percentage between 17.5% and 25% is considered heavy loam. Anything above 25% is considered clay soil.
Clay loam is found in various parts of the Netherlands, particularly in the transitional areas between clay and sandy soils. The properties of clay loam vary depending on the ratio of its constituents, but generally, it has moderate permeability and retains water well. This means that clay loam retains water better than sand, but is more permeable than, for example, pure clay or peat.
When dewatering in loam soil, the moderate permeability must be taken into account, requiring a balance between sufficient groundwater drainage and preventing subsidence. At Bronbemaling.com, we always work precisely and ensure that water in loam soil is effectively drained while preserving the soil structure.
Clay
17% of Dutch soil is called clay soil. This is a very fine soil type found primarily in low-lying areas of the Netherlands, such as polders and river deltas. Clay has a very high water retention capacity but low permeability, meaning water moves slowly through this soil type. This can pose a challenge for wellpoint dewatering, as removing groundwater from clay soils often requires a slower and more careful process. Incorrect dewatering can disrupt the clay structure, leading to instability and subsidence. Therefore, when dewatering in clay soils, it is essential to have a detailed plan and continuously monitor dewatering activities to ensure an efficient and safe process.
Marine clay is a fine, compact soil type found primarily in coastal areas of the Netherlands. It has low permeability to water, meaning groundwater moves slowly through this layer. When dewatering in areas with marine clay, it’s important to consider the slow drainage of water.
River clay, found in areas surrounding rivers, is similar to marine clay in terms of permeability but has a slightly different composition due to the deposition of river silt. Here too, the challenge in wellpoint dewatering is its slow permeability. Designing a drainage system that takes the specific properties of river clay into account is essential for effective groundwater management.
Peat
About 9% of our country consists of peat soil. Peat is an organic soil type formed by the accumulation of plant remains. It is common in low-lying areas of the Netherlands. Peat is highly water-retentive, but it collapses when the water is pumped out, posing a challenge for wellpoint dewatering. It is important to carefully regulate dewatering to prevent subsidence, a common phenomenon in peatlands. Also read all about subsidence and inversion.
Swampy grounds
Peat soils on sandy soils comprise approximately 2% of Dutch soil. In soil classification, peat soils represent the transition from peat soils to mineral soils, such as sand and clay. This soil type consists of a thin top layer of organic material, such as peat, with a mineral subsoil. Due to this unique composition, peat soils have properties similar to both peat soils and sandy and clay soils, making wellpoint dewatering particularly challenging. Despite the slower compaction compared to pure peat soils, the stability of this soil type remains a key concern in wellpoint dewatering.
Clay
Only 2% of Dutch soil consists of loam. Loam is a soil type that is finer than sand but coarser than clay. This composition gives loam moderate permeability to water. In loamy areas, wellpoint dewatering must consider the specific balance between water retention and permeability. Overly aggressive dewatering can lead to subsidence or uneven ground subsidence. As with clay, it is essential to proceed carefully and monitor continuously to ensure the soil remains stable and that no unexpected problems arise during the dewatering process.
Different soil types and wellpoint dewatering
It is essential to fully understand the properties of both the soil and the groundwater before dewatering begins. Each soil type reacts differently to dewatering, and an incorrect approach can lead to serious problems, such as subsidence, subsidence, or even damage to surrounding buildings and infrastructure. For example, sandy soil requires constant monitoring due to its rapid water movement, while clay and peat must be dewatered carefully and slowly to prevent subsidence and subsidence. Loam and clay, both of which have moderate permeability, require a careful balance.
To ensure proper water level management without soil instability, we utilize various drainage techniques. For soils with coarse layers, such as sand or gravel, we use gravity drainage . Tension drainage , on the other hand, is used in drainage projects to reduce water pressure beneath a barrier layer, such as clay or peat. However, with poorly permeable soils, such as clay or peat, vertical drainage is not always effective enough. In these cases, we use horizontal wellpoint dewatering .
We also use various methods to maintain groundwater levels and protect the surrounding area. For example, we utilize reverse pumping , where drained groundwater is pumped back into the ground to prevent the water table from dropping too low. This is essential for ensuring soil stability and preventing, for example, subsidence in the surrounding area. We also use rewetting filters, particularly in areas with peat or clay, to keep these soils moist and prevent compaction .
Different soil types for your water issue?
Wellpoint dewatering in the various soil types of the Netherlands is a precision job that requires thorough knowledge of the local geology. Each dewatering project must be carefully planned and executed, taking into account the specific properties of the soil type, to effectively and safely manage groundwater. At Bronbemaling.com, we understand the importance of choosing the right dewatering techniques for each soil type. That’s why our experts always conduct a thorough soil investigation and then adapt the dewatering techniques based on the specific needs of each project. Whether it’s a large construction project in sandy soil or a smaller dewatering project in clay soil, we always ensure safe and effective groundwater drainage.
