How to install an attenuation tank

Posted by Callum Vallance-Poole, on July 16, 2024.

GRAF UK Install Team

Stormwater attenuation tanks play a vital role in managing surface water runoff and mitigating the risk of flooding in urban environments. By capturing, storing, and gradually releasing excess stormwater, these tanks help alleviate pressure on drainage systems and protect surrounding areas. However, the effectiveness of a stormwater attenuation tank hinges on its installation.

How to install a stormwater attenuation tank

Initial Safety Inductions and Site Preparation 

Before any installation activity, the GRAF UK team engages in a thorough safety induction to understand site-specific rules and health and safety measures. This foundational step ensures that all team members adhere to safety protocols throughout the project.

Detailed Excavation and Preparation 

The installation process begins with the excavation for the tank. The main contractor typically carries this out, ensuring the excavation meets the specified dimensions. It’s important that the base of the excavation is level.

Preparing the Base:

We layer the base of the excavation with non-angular, single-sized stone (8mm to 16mm) to a minimum depth of 50mm, creating a solid and flat foundation that prevents water from undermining the structure.

The excavation needs to extend at least 500mm beyond the planned tank area to facilitate safe and easy tank installation.

Assembling and Placing the Tank

Base Layering: GRAF UK lays a geotextile layer followed by a geomembrane, extending both slightly beyond the tank’s perimeter. This ensures stability and prevents shifting during the installation.

Crate Installation: Attenuation crates are placed onto the geomembrane, connected by clips, and checked for alignment and stability.

Membrane Welding: Membrane seams are carefully welded to form a watertight barrier, crucial for the tank’s effectiveness in stormwater management.

Pipe Connections: Both low- and upper-level connections are installed and meticulously sealed to connect the attenuation tank to the rest of the necessary pipework on site.

Protective Measures and Final Steps

Geotextile Covering: A final layer of geotextile covers the tank, protecting it from debris and mechanical damage during and after the backfill process.

Vent and Inspection Installations: Vent connections are installed and sealed to ensure the tank is appropriately vented.

Backfilling and Compaction

Once the textile is covering the tank, backfilling begins with well-graded gravel or shingle. This step is critical for providing structural support to the tank and protecting it from external pressures.

Proper compaction ensures the backfill tightly surrounds and supports the tank, enhancing its longevity and performance.

Choose GRAF UK for End-to-End Stormwater Solutions

Opting for GRAF UK not only provides you with a high-quality attenuation tank but also ensures a comprehensive installation service from initial planning and design to final installation. Our team’s expertise in stormwater management guarantees that your project will meet all performance and regulatory requirements. Contact GRAF UK today if you are looking for an expert team to install the attenuation tank on your next project.

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