Brief project information:
| The location: | The River Weaver Navigation |
| The project: | To flush out 30,000m3 of silt from a six mile section of the River Weaver using suction and floating dredging. The silt was restricting safe access for vessels and reducing oxygen levels in the water. |
| Timescale: | - |
| PDF: |  Download case study - River Weaver |
“I had used Blue Boar in the past and was keen to get them back as their performance was very good. Their ability to find an appropriate solution was a real differentiator.”
Neil Rice, Senior Engineer – Wales and Border Counties Business Unit, British Waterways.
The location:
In the 17th century, the River Weaver was a shallow tidal stream used to transport salt from the Cheshire salt areas. In 1721, the river was made into a navigation from Frodsham to Winsford – and by 1732, it was fully navigable for up to 40-ton barges.
The River Weaver navigation now runs for 50 miles between the Manchester Ship Canal and Frodsham and is used primarily for pleasure use and the mooring of ocean-going yachts at Northwich. The Anderton Boat Lift, used in the 18th and 19th centuries to move barges and narrowboats from the Trent & Mersey Canal is also a key tourist attraction.
The project:
The Weaver navigation must adhere to certain standards so that it can be used properly by the traffic that travels along it. Below Winnington, this means a depth of 3.2m and a width of 10m, with a depth of 2.67m between Winnington and Winsford. Regular maintenance is required, especially near locks and tributaries.
In 2005, the annual hydrographic survey identified a number of ‘high spots’ on the river bed. These ‘high spots’ can make it difficult for the yachts moored at Northwich to get through, not to mention the larger commercial vessels that use the River Weaver every year.
Why Blue Boar?
The Wales and Border Counties Business Unit of British Waterways had two suppliers to choose from but they chose us because we’d worked with them before and they had been impressed by our flexible and creative approach.
The challenges:
- The Weaver navigation contains a number of locks which have been in place for over 200 years. Silt can build up quite considerably around them and there were various ‘high spots’ upstream of Dutton Locks, up and downstream of Saltisford Locks and along a 200m length at the Town Bridge section.
- The silt around Dutton Locks had a jelly-like consistency which made it hard to dig out using a normal excavator. To cope with this and to stay within budget, we used suction dredging which is more economical and gives a better result.
“We were pleased with Blue Boar’s work – and with their adaptability to meet our requirements via different methods. To use floating dredging throughout would have been beyond our budget but Blue Boar found a way round it for us.”
Heather Airlie, Project Manager, British Waterways.
The outcome:
Just over 30,000m3 of silt was removed using floating and suction dredging. With suction dredging, there is no need to physically move excavated silt; instead, we created a 200m channel along the side of the river to pump the silt through and carry it away downstream.
The remainder of the dredging was carried out using a standard excavator on a floating pontoon.
The excavated silt was transferred onto barges and taken to British Waterway’s own tip as this was the most cost-effective disposal method.
Public sector and Large commercial contracts
In this section
- Droitwich Barge Canal
- River Weaver
- The Grand Western Canal
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