Restoration of a historic low flow channel within a tidal environment Tidal Desilting and Associated Earthworks

The ultimate goal for our client was to achieve an improvement in the gravity drainage function of the main drain tidal channel from Dock Bridge outfall to the confluence of Wrea and Liggard Brooks.

The project consisted of disposing of historical silt placed on the embankment berm and toe of the embankment, as well as restoring the historical low flow channel.

This project was complicated by a number of factors; The Ribble Estuary contains a number of important environmental designations.

The Lytham Coastal Changes Geological Site of Special Scientific Interest, resides alongside approximately 200m of the tidal main drain.

The works needed to be conducted in an area affected by tidal range leading to the site being periodically submerged and the tidal channels were utilised by the local yacht club for moorings and access. Traffic management also needed to be imposed during the works.

Prior to works commencing Ebsford performed an additional step of conducting its own long section gradient survey to compare with the initial tender documentation. By doing so we were able to identify that working in the lower stretch which was initially specified, would not provide any benefit to the overall aims of the project. As a result the focus was able to be moved to the upper stretch, where more silt could be removed, further protecting that part from slumping of the soft banks.

The disposal of the 1500 m3 of material, originally deposited there in the 1980’s when the last major desilting works were performed was also able to be reduced. Due to the length of time the silt had been there and with vegetation having grown over it like any typical earth bank, we were able to redesignate the silt as soil.

As a result of our efforts we were engaged to provide Early Contractor Engagement (ECI) on some of the adjoining watercourses as part of preparations to improve the wider catchment.