A smarter approach to site drainage: introducing the new Coverblok range

At Turtle Enviro, our mission is to deliver practical, high-performing solutions that help developers meet environmental standards and improve on-site drainage performance.

Our newly updated Coverblok range continues that commitment, providing a simple, low-cost solution for preventing surface water contamination during the construction phase.

With the WIS 4−26−01 standard for leak-tightness now in effect and continued focus on S104 adoption and Design and Construction Guidance (DCG) compliance, Coverblok offers developers an effective way to reduce pollution risks caused by silt and debris entering the surface water drainage system.

Why Coverblok?

Construction site roads and uncovered or poorly sealed manholes pose a significant threat to surface water drainage systems.

If left unmanaged, they can allow large volumes of silt and debris to flow into the network, potentially clogging pipes and causing downstream flooding or contamination of wetlands, ponds, and watercourses.

Implementing a reliable silt prevention system is not just a regulatory requirement; it is a vital part of protecting the long-term performance of Sustainable Drainage Systems (SuDS) and preserving the integrity of the surrounding environment.

Coverblok is designed specifically to address this issue. Installed beneath access or manhole covers, it acts as a barrier that stops unwanted materials from entering the system through gaps between the cover and frame.

Moulded from recycled plastic, this product offers a cost-effective alternative to traditional metal solutions, while also delivering durability, reusability, and environmental benefits.

By implementing Coverblok early in the construction phase, developers can reduce pollution risks, meet regulatory obligations, and demonstrate a proactive commitment to sustainability.

A two-model range, built for performance and compliance

Coverblok is available in two models:

Standard model

This model features a fully sealed lid, designed in line with the latest WIS 4−26−01 UK Water Industry standard for leak-tightness.

This ensures long-term reliability by preventing silt ingress during the construction phase and supporting compliance with both current and future industry regulations.

Its recessed lifting handles help protect against damage during maintenance and improve usability, resulting in a longer service life and more efficient on-site operation.

Filtered model

This model includes all the features of the standard model, with the added benefit of our Siltblok filter integrated into the cover.

This unique filter effectively removes particles from the discharged water by acting as a brake that disrupts particle velocity, causing them to settle out of suspension. This helps prevent the flush-through of silt and other materials when the space under the cover is full.

The Siltblok filter offers high-efficiency filtration across a wide range of particle sizes. In independent testing, it achieved the following performance results:

• Particles above 75 microns: 95 percent removal on first use, improving to 99 percent with continued use
• Particles below 75 microns: Between 50 and 70 percent reduction, depending on concentration

Its design also ensures continued operation without full clogging, reducing the need for regular cleaning or replacement.

Both models are manufactured from high-density polyethylene (HDPE), providing a robust and reusable solution that is easy to handle and suitable for reinstallation on future sites.

Available sizes

Coverblok is available in two sizes, suitable for the majority of access chamber applications:

• CB8585: 675 mm x 675 mm clear opening
• CB14085: 1250 mm x 675 mm clear opening

The standard variants are designated CB8585MP and CB14085MP, while the filtered versions are CB8585MPF and CB14085MPF.

A design built with sustainability in mind

Sustainability is at the core of Coverblok’s design. From the use of recycled and recyclable materials to its reusable build quality, the product offers a more environmentally responsible alternative to single-use or disposable silt protection solutions.

Made in the UK and developed to help contractors meet the latest industry standards, Coverblok combines high-quality engineering with a low environmental footprint.

Whether used in its sealed or filtered form, it delivers consistent and reliable protection for surface water systems and the environment during the construction phase.

For further information, installation guidance, or pricing, contact our team today.