Tyne Rivers Trust
Lintford Mill, Rowlands Gill
- Contract Value:
Lumsden & Carroll deliver a civil engineering solution, investing in the local environment, to aid the passage of fish up the River Weir.
The scheme comprised the construction of an all new 15m long, 4m wide fish pass to the corner of the Lintzford Mill weir on the River Derwent to aid the passage of fish up the river to more suitable spawning grounds.
The River Derwent is a swift flowing small lowland river flowing over exposed bedrock, cobbles and gravels. The banks comprise of semi natural and manmade stone revetment. Lintzford Weir is a significant 2m high masonry structure of the River Derwent that has been in place for over 300 years. It is a major barrier to the upstream migration of salmon and sea trout.
The works undertaken comprised of:
• Dewatering measures to divert the flow of water away from the works location; via the use of sand bags and small pumps. The sand bags were placed on a section of the weir crest diverting flow away from the works location.
• The creation of the rock ramp from large armour stone, each roughly 1.5 – 2 tonnes in weight. The stone and associated rock were placed in a tightly fitted formation to create stable cross weirs, which formed a series of pools each roughly 200mm lower than the one immediately upstream.
• These large stones were fixed to the principal masonry weir structure which was stone penned to the river bed, using a concrete fitting and beneath each cross weir that was reinforced with galvanised bars and grout.
• Large rock bank protection works were undertaken as part of the project comprising of fully reinstating the left bank to its original condition to blend into the surrounding landscape.
Due to working within a live natural watercourse, sediment management measures were utilised such as “booms” to protect the river and quality of spawning habitat for the targeted fish species.
Thank you very much for all the work you have done over the past weeks and for putting up with our continuous site visits. The fish pass we have constructed is reckoned to be up there with some of the best examples in the country so well done to you all.- Douglas Phillips, Tyne Rivers Trust