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Lining tanks: essential for water security

04 November 2024

Lamination ponds and hydraulic invariance: a necessary balance for water security

Lamination basins are essential tools for ensuring hydraulic invariance, a fundamental principle of sustainable rainwater management. This concept, introduced by regional regulations such as Regulation No. 7 of the Lombardy Region, stipulates that stormwater runoff from urbanized areas should not exceed pre-existing flow rates. When an area is sealed due to urbanization, the natural capacity of the soil to absorb water is reduced, increasing the risk of flooding and overflow. Litter ponds can mitigate this effect by temporarily storing excess water and gradually releasing it into natural or man-made receptors. This approach not only reduces hydraulic risk, but also promotes hydrogeologic re-balancing, contributing to more efficient and safer stormwater management.

 

What are laminar flow basins and how do they work?

In an environment increasingly characterized by the risk of extreme events and very heavy, sudden and short-lived rainfall events, lamination basins, also known as retention basins, are probably the best solution to reduce the risk of hydrogeological hazards and the consequent impact on the environment and people

How do they work? Lilting ponds are hydraulic structures designed to regulate the flow of rainwater. During heavy rain events, they collect excess water as a temporary reservoir. They then release it in a controlled manner to reduce stream flows and prevent flooding

Reservoirs can be either buried (i.e., below the surface of the ground, "hidden" from view) or open-air, which are then visible and designed to blend into the landscape as much as possible. Open ponds consist of a large area of land that allows excess water to accumulate and then drain away: they are essentially depressions where water is channeled.

Laminator tank sizing

Proper sizing of the laminating basin is a crucial aspect that must be carefully considered based on the requirements and geomorphologic and climatic characteristics of the area where it will be installed.

 


A lamination basin generally consists of

  • An intake structure to convey excess water to the lamination basin. This may be a culvert or drainage pipe that collects incoming water from the adjacent watercourse;
  • A reservoir. This is the central part of the laminating basin, a depression, a large area of land capable of holding water;
  • A drainage device that allows the reservoir to be emptied when the rainfall has passed and the stream flow has returned to safe levels. Drainage can be by gravity or by pumping.

 

Management of first rainwater

Another key aspect of rainwater management is the management of first rainwater. What it is.

First rainwater represents the initial part of a meteorological event that, when it flows over impermeable surfaces, generates a significant runoff of accumulated substances.  Italian legislation, for environmental protection purposes, conventionally identifies it as the first 5 mm of precipitation per square meter of impermeable surface served by a drainage network.

First rain water must be separated from "second rain" water (i.e., water that precipitates in the next 15 minutes) and treated before final discharge. The reason for this is that they can carry pollutants present on the runoff surface.

The amount of impervious surfaces, usually for productive and/or commercial uses, has increased considerably, especially in urban areas. Therefore, the risk of accumulation, stagnation and pollution of the first rainwater, before it drains, has been very high. It is therefore crucial to manage the surface runoff of these waters.

For this reason, Italian law has established regulations that require the collection and treatment of rainwater that falls on impermeable surfaces. This is necessary, as we have already said, to prevent the release of materials such as sand, clay, hydrocarbons, oily residues, particles of consumable materials and others into waterways or sewers.

The first stormwater treatment systems are therefore used to serve impermeable surfaces (these can be industrial yards, intermodal areas, ports and airports, roads...). They are generally installed to facilitate the disposal of water by infiltration into the ground.

IDRO Group's water treatment solutions

Today, IDRO Group is a benchmark in the field of rainwater treatment, offering state-of-the-art solutions for the protection of the territory and its resources.

In particular, the company is involved in the analysis, design and implementation of a wide range of stormwater treatment systems. The company has developed specialized stormwater treatment systems; these are solutions suitable for small, medium and large areas. Among the many solutions offered, we find both de-oiling plants and specific plants for the treatment of first rainwater.

The company is also involved in the construction of precast concrete flood wave rolling basins. These precast basins reduce the amount of runoff in the sewer and mitigate hydraulic risk. The use of one-piece, prefabricated tanks allows for a greatly simplified process and faster installation, even where there is a surface water table. 

Thanks to its long experience in the field, Idro Group is able to advise and guide the customer in choosing the most suitable rainwater treatment system for his needs. Please do not hesitate to contact us if you have any questions.

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