The challenge
Working on behalf of Scottish Water, Caledonia Water Alliance (CWA) was contracted to design and construct a new support structure to shore up the riverbank. However, with the River Ericht one of the most important spawning grounds for migrating Atlantic Salmon, the construction works were limited to a narrow time window between June and October.
An additional challenge was the location of the local Wastewater Treatment Works (WwTW) adjacent to the river, with the only vehicle access road to the Scottish Water site running alongside the bank and the main inlet pipe crossing over the river. Given the ongoing erosion, the WwTW presented clear safety concerns. Maintaining safe access for all vehicle traffic along the access road was essential to ensure there was no interruptions to the daily operational running of the WwTW, with one section of embankment only measuring one metre in width between the road and river. The manual inspections were also raising health and safety concerns, given the proximity to live and fast flowing water.
Reaching the end of the safe working window for the year, the focus had to shift to ensuring the riverbank was kept safe throughout the 2024/2025 winter period, with further heavy storms forecast.
Our solution
Working closely with CWA, we developed a bespoke monitoring solution to provide valuable insight and an early warning system of any structural damage. This included the use of our 40 No wireless bi-axial tilt sensors and 20 No tilt sensors, which were mounted on ground spikes directly into the embankment during the ground stabilisation process. As the works were adjacent to an access road, 20 No tilt sensors were also located on the road edge. The system was installed for 36 weeks during the works.
Locating the sensors was a carefully thought-out process. Given the instability of the embankment, there were concerns that the sensors could fall into the river or even be entirely washed away if water levels rose. As such, our monitoring team had to strike a balance between safe sensor locations and the need for accurate data. There were also temperature differentials to consider, ranging between -7ºC and 27ºC, with the potential for the bank to shift and expand with the temperature changes.
Installed in January 2025, the sensors remained in place until April 2025. The CWA team remain on site, installing the 220 metres of piled supporting wall.
