Lagoon Lining | A23, Brighton, UK

Two Attenuation Ponds Lined with CCHT1^™

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Project Overview

In October 2023, CC Hydro^™ GCCB was used to line two attenuation ponds near the A23 north of Brighton, UK. Originally constructed in the early 1990s, the two attenuation ponds were designed to capture runoff water from the A23 and prevent the drainage system becoming overwhelmed in a storm event. Due to the contaminants in this run off it was vital that an impervious surface was installed, a 0.75mm geomembrane with a concrete paving slab cover layer was used in the first instance. Over time, the two attenuation ponds became overgrown with vegetation, with some of the paving slabs becoming dislodged affecting the protective cover to the geomembrane.

Attenuation pond prior to works

Excavators used to remove vegetation

4000m²

of CCHT1^™ lined two attenuation ponds

70m²

of CCHT1^™ installed per day

Solution

Due to the liner being damaged by tree roots and other vegetation, the consultant and their client, National Highways (previously Highways England), had concerns about water from the two ponds seeping into the surrounding areas. The consultant looked at removing the liner and concrete slabs and replacing with a new HDPE liner, with the Concrete Canvas^® GCCM laid on top as a protection layer. A representative from Concrete Canvas Ltd suggested using the CC Hydro^™ GCCB instead as a combined, all-in-one alternative solution, installed over the existing liner and concrete slabs to save on construction costs. CC Hydro^™ could maintain pond capacity and reduce permeability, provide resistance to puncturing/damage and reduce maintenance by preventing vegetation growth.

CCHT1^™ installed over geotextile, hydrated and secured with clamping bars to concrete structures

Design & Installation

Vegetation removed, loose slabs repositioned
Geotextile laid to protect CCHT1^™ geomembrane backing
CCHT1^™ Bulk Rolls specified
Perimeter edges secured in anchor trenches
Connected to infrastructure using clamping bar and anchors
Thermal welded joints air channel tested to verify strength and permeability
Pipe boots formed with PVC geomembrane and welded
Hydrated after each shift using hose and water

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CCHT1^™ overlapped and thermally welded

Summary

The first pond was completed in 2 weeks with approximately 70m² of CCHT1^™ installed per day. During the installation of the second attenuation pond, poor weather conditions meant that outlet pipes within the pond had to be bunged. However, these had to be removed every night resulting in the pond filling with water and needing to be drained the following morning. This reduced productivity but enabled the ponds to maintain their function during periods of heavy rainfall.

National Highways were pleased with how the material was installed and the final results. The CC Hydro^™ remediation will provide effective containment and weed suppression, extending the operational life of the ponds.

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