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 Millheugh – were identified by the Rivers and Fisheries Trust of Scotland as particularly obstructive to fish, as they close off large areas of riverbed.
Following a feasibility study carried out by design and project management consultants Atkins Ltd, the preferred option for opening up these inaccessible areas to spawning fish was through the construction of fish ladders.
As a result, Blockwalls was chosen to supply its Stackabloc 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.
Colourcrete uses a unique, fully automated liquid pigment dispensing system, which allows the exact dosage to be applied, ensuring that batches produced at different times consistently match. The liquid pigments contain the highest solid content and are dispersed easily in the concrete mixes to produce high intensity colours, which are UV stable.
Bob Evans, managing director of Blockwalls, said: “The quality of the coloured concrete supplied by Hanson was spot on and the support we received from the technical team ensured that the production of the blocks went very smoothly. The 200 two-tonne interlocking blocks have been used to great effect to create the new fish ladders, which have resulted in around 200 kilometres of river being opened up to spawning fish.”