Scotland has long-harnessed water energy through weirs and other structures. Although power is now largely sourced from other industries, many of the weirs still remain, preventing fish species such as salmon from migrating upstream to their natural spawning areas.

Two abandoned weirs on the Avon Water in South Lanarkshire – Ferniegair and Millgheugh – were identified by the Rivers and Fisheries Trust of Scotland as particularly obstructive to fish, as they close off large areas of the riverbed

Following a feasibility study carried out by design and project management consultants WS Atkins Ltd, the preferred option for opening up these inaccessible areas to spawning fish was through the construction of fish ladders

The Challenge

Blockwalls was approached by WS Atkins and supported the design process working out ways that the blocks could be anchored to the riverbed. Ducts where cast into the blocks at 800mm centers to allow the blocks to be bonded together and anchored to the river bed rock. 25mm rebar was used as the reinforcement and was grouted in with a non shrinkable grout.

The Solution

Blockwalls was chosen to supply its Builder block 1.6m x 0.8m x 0.8m x 2.5 tonne heavy duty interlocking wall blocks to form the fish ladders. The blocks needed to blend with the clay riverbed and, after a series of trials, Hanson Colourcrete in Straw was specified as the best match.

Fish Ladder Construction

The civil engineering contractor was George Leslie Ltd of Glasgow. George Leslie were ideal to execute this project from the impressive civil engineering experience. Blockwalls worked closely with George Leslie to ensure the right blocks were delivered at the right time for site production. Access to the site was created by laying a stone road along the riverbed that was removed on completion of the works.

The 480 tonne of interlocking blocks have been used to great effect to create the new fish ladders, which have resulted in around 200 kilometres of the river being opened up to spawning fish

Blockwalls supported WS Atkins and George Leslie with 3D design drawing to see how the blocks worked and for the team to visualise the project. If you have a project and you think concrete interlocking blocks can be used, then make contact. We are very friendly and love a challenge.