In May 2014, civil engineering works commenced on a new community funded hydroelectricity and fish pass scheme on the River Calder in the village of Whalley in Lancashire, with a project value of £280,000 and a highly constrictive 22 week programme incorporating all aspects from initial site clearance, excavation and construction of the channels and crane pad.
Excavation works posed many challenges requiring robust solutions. The base of the excavation at its deepest is around four metres below the upstream river levels, a serious risk if not correctly managed. This mass of water was controlled through the use of double rows of six metre Larsen piles retaining a soil infill to keep any water ingress to an absolute minimum. However, the water continued to cause problems as the works created a barrier for ground water from the surrounding landscape with the continual seepage requiring pumps to manage any build up. The design for the project
also required amending as this water could not be permitted to build behind the structure and french drains were incorporated to alleviate this issue.
The excavations continued to provide us with new challenges. Throughout history, the river has meandered across the landscape, with our works being on the inside of this river feature. As the excavations continued it became more apparent the works has reached the silt and rock from the historic riverbed. Naturally, the riverbed, contains an assortment of rock and soft spots, all of which had to be resolved as discovered to keep the work progressing.
The original weir and river walls were constructed around 800 years ago by the monks at Whalley Abbey. The wall required removing both upstream and downstream of the weir for the new channels and so provided an insight into the original construction as the excavation revealed more about the walls; some of the stones, weighing several tonnes required breaking in order to be removed.
This project has been initially funded by the local community, with residents in the surrounding area having the option to purchase shares and have their own influence over the long-term views of Whalley Community Hydro.
As a considerate contractor, we are obliged to work with the local community, in particular the new schemes’ neighbours. Construction traffic and noise was monitored on a regular basis. The use of silent pumps to deal with water ingress overnight and regular contact with third parties, especially those who will share the lane with the new scheme, it was essential to maintain positive relationships. Another important neighbour is the farm that has leased the land to Whalley Community Hydro and it was essential daily access was maintained along the lane beside the works.
The scheme received recognition as the delivery of the Archimedean screw was covered by the regional press, both in print and visual media. A strong turnout from the public also assured that the scheme was in good favour with the wider community.
An added bonus for the scheme, is the receipt of what will hopefully be the first award of many; ‘Start-Up of the year’ at the UK Community Energy Awards 2014.