Retainer-Rock® walling installed at Cardigan Wastewater Treatment Works

The replacement of Cardigan Wastewater Treatment Works follows extensive work in after it was identified that seawater was entering the site from the tidal river, especially during the spring high tides, causing local storm overflows to discharge more than they should into the local estuary, however bathing waters in the area continued to meet ‘excellent’ water quality standards, as monitored by Natural Resources Wales.

After carrying out extensive trials and installing two pilot treatment plants at Cardigan, Welsh Water identified a process using moving bed bio-reactors. This process has proven to be the most effective in reducing the severity of incoming seawater, helping to reduce its impact and improve resilience at the works.

Work to install the new treatment works began in April 2025 and included a retaining wall structure to help protect the multi-stage processing works, which removes pollutants, organic matter and disease-causing organisms from used water.

Retaining walls on these processing works need to serve a practical purpose, while also providing a durable, tidy finish. Retainer-Rock® combines the strength of precast concrete with a natural stone appearance, making it suitable for projects where both engineering and appearance matter.

The interlocking blocks are manufactured offsite and delivered ready for installation They are dry laid, allowing the wall to be assembled without mortar, making installation easier and quicker than traditional retaining wall methods. Morgan Sindall built a 3m high curved wall that was 500m long using standard blocks that retains the two treatment plants.

Elite Precast offers the retaining system in Cobblestone and Liscio Stone finishes, with straight or curved layouts possible using standard blocks. The appropriate wall design depends on the site’s ground conditions, loading and required height.

The Cardigan installation demonstrates how modular precast walling can be incorporated into a wastewater infrastructure project. By installing Retainer-Rock®, Morgan Sindall has created a concrete retaining wall with a finished face suited to its surroundings.

For contractors planning retaining walls on water, utilities or other infrastructure sites, Elite Precast Concrete can provide product information and guidance on the Retainer-Rock® system.