Updated 26 August 2024. Next update: Friday 20 September 2024.
The current situation
Rock armour consolidation is now 100% complete, and the dive inspections to check this work are also complete.
The overall project is now around 45% complete, a fantastic effort from our Contractor and Supervision teams.
Work has now started to build the toe wall at the foot of the original harbour wall. The purpose of this is to prevent any further loss of seabed material from around the base of the original wall and protect the wall against wave and wash from vessels using the harbour.
The first section of toe wall is between to the two areas of rock armour that have been consolidated. Work involves digging a trench to place bolster bags in. These bags are then filled with concrete and tie together using reinforcing bars. The wall is built in steps, allowing each layer of concrete to harden before the next layer is placed.
The skilled construction divers have to move carefully when filling the bolster bags and be careful not to tear them. A difficult job whilst working beneath the water.
Previous work
The contractor started work, on site, on 27 May as planned and compounds have been set up on the main Rothesay Harbour pier and the Albert Pier, which will receive material deliveries. Plant and equipment, including a crane and barge, have been delivered to the site.
Divers and engineers have begun working on night shift. The have carried out a number of dives to establish the situation beneath water level. This includes:
- carrying out safety checks and rescues drills to ensure the safety of the dive team when working in the water:
- checking previously surveyed information and comparing that against what divers are observing beneath the water. We will then know if the bed has changed in a significant manner since the previous survey; and
- establishing control points for use throughout the works.
Concrete works may begin soon so people may see concrete lorries on the pier at night from now on.
Rock armour at the west corner of the pier has been fully consolidated with concrete. Around 80 cubic metres of specialist, underwater concrete was carefully placed amongst the rock armour to 'glue' the rocks together to create a mass. This will prevent any slumping of the rock armour, further protecting the wall at this corner.
The second area of rock armour located immediately in front of the ferry terminal building had to be consolidated. The length of pipework needed to pump concrete from the delivery mixers around the building and into the rock armour at the foot of the seabed has made this challenging. The pipework, known as a tremie, was around 25 metres long and, because of this length, the team used smaller quantities of concrete to test the pipe run and to ensure minimal waste should an issue occur. Doing the test run allowed the team to find solutions to issues during the first night of concrete pours so that it could be placed successfully.
Tests with a smaller sized aggregate - to minimise blockage of the pipe - were successful with no detriment to the concrete mixture. The Contractor's team was able to continue to pour concrete in small quantities to consolidate the second area of rock armour.
The Contractor stockpiled 'bolster bag' materials in preparation for the next stage of the works, to construct the toe wall in front of the remaining parts of the wall.
Background
Works at Rothesay Harbour will support the future of the pier by preparing it to accommodate larger, more powerful vessels than the original pier was built to withstand.
Â鶹Ãâ·Ñ°æ and Bute Council has appointed Shearwater Marine Ltd to undertake £1.9m stabilisation works at Rothesay Harbour. Maintaining ports and harbours is just one of the services our council provides that others don’t need to.
The contractor will mobilise at the harbour during the week beginning 20 May and the first dive is scheduled to take place on Monday 27 May
Shearwater Marine Ltd will carry out work overnight to minimise disruption to ferry operations and day-to-day travel for Bute residents and visitors should be mainly unaffected.
However, to allow the contractor access to the site, the berth will not be available overnight. This will mean one of the Bute ferries will berth overnight in Gourock.
Work should take nine months to complete, and this is dependent on the weather and supply of materials.
Stabilisation works at the harbour include:
- Constructing a toe (retaining) wall at the base of the original wall to provide stability to the main harbour structure. This will extend 143m from the eastern edge of the harbour wall to the overnight ferry berth
- The toe wall will prevent any potential sliding or further loss of fine materials from the sea bed behind the original wall.
- Repair to the surface of the harbour where there has been visible settlement.
This new work builds on previous investment at the harbour to minimise scour, and so mitigate damage done by vessels over the years. Scour is when the seabed is dug out by vessels moving the water and creating channels against the harbour wall. We fitted a wavescreen which prevents vessels moving the water and creating scour and so protects the harbour wall. Since the wavescreen was fitted, we have seen a notable reduction of settlement on the top of the harbour wall.
For information on revised ferry timetables visit the .