Replacing aged concrete with high-integrity solutions
location
Sussex
The Challenge
The project required works in tidal conditions within a live river environment where flow speeds, access, and timing were key constraints. The existing revetments were failing, creating erosion and stability risks along the embankments, and standard repair techniques were unsuitable due to the site’s exposure to fast tidal flow and variable substrate.
The challenge was to deliver a durable, low-maintenance solution that could be installed efficiently between tidal windows while integrating with existing riverbank protection systems.
The Solution
HEP delivered the works in two phases, in 2014 and 2018, using asphalt-based materials to provide resilient, watertight protection against the River Arun’s demanding tidal conditions.
In the 2014 phase, the slope was re-profiled and a new toe formed within the existing embankment. A 150mm layer of Open Stone Asphalt (OSA) was placed over a 150mm filter layer of Lean Sand Asphalt (LSA) to stabilise the structure, with irregular top edges sealed using hot-poured mastic to ensure water-tightness and durability.
In 2018, further upstream, damaged concrete-filled mattresses were removed, the surface regulated with LSA, and 150mm of OSA installed flush with the remaining mattresses. All edges were again sealed with hot-poured mastic for long-term integrity.
How We Delivered
Working within tidal constraints required meticulous planning and sequencing. Each phase was programmed around tidal windows to ensure safe access and high-quality placement. Materials were delivered and compacted under controlled conditions to maintain consistency and performance, with crews experienced in fast-flowing waterway environments.
This systematic, high-integrity approach allowed works to be completed efficiently over a combined three-month period, with minimal disruption to river operations and surrounding habitats.
Community & Environment
Environmental protection was a central consideration throughout the project. The River Arun forms part of an important ecological corridor, and all activities were carefully managed to prevent silt mobilisation and contamination.
The use of durable asphalt layers provided a long-term solution with no ongoing maintenance requirement, reducing future disturbance to both the river and surrounding environment. The completed works strengthened flood protection and improved resilience for the local community.
The Outcome
The River Arun revetment replacement provided a robust, low-maintenance solution that continues to perform effectively under one of the UK’s most demanding tidal regimes.
By combining Lean Sand Asphalt (LSA) and Open Stone Asphalt (OSA), hep delivered a flexible and watertight system that integrated seamlessly with existing defences. The project enhanced riverbank stability, improved flood protection, and demonstrated how durable materials and precise delivery can extend the life of critical tidal infrastructure.
