Dunoon Sewage Scheme


ABCO Marine Ltd were contracted by Galliford Morgan Joint Venture Ltd as specialist marine subcontractor on Dunoon Sewage Scheme for Scottish Water. The project design detailed seven separate outfall pipelines, of varying size and length; 

  • Milton Burn Outfall – 1100mm 1600mm OD Pipe, 185lin/m 
  • West Bay Outfall – 1100mm OD Pipe, 135lin/m 
  • Jim Crow Outfall – 710mm OD Pipe, 85lin/m 
  • Ardnadam Outfall – 710mm OD Pipe, 236lin/m 
  • Sandbank Outfall – 355mm OD Pipe, 285lin/m
  • Holy Loch Outfall – 355mm OD Pipe, 205lin/m
  • Bullwood Quarry Outfall – 355mm OD Pipe, 140lin/m 

BCO Marine Ltd supplied and prepared the outfall pipe lengths, with the pipe welding on site with quality control records maintained, with all precast concrete collar ballast connected, and the pipe strings pushed out and retained before sinking. The prepared pipe lenghts were then twoed on average 8 naughtical miles to the various work locations.

Project Information

Seven number Outfalls into Firth of Clyde, employed as specialist marine contractor for outfall installation for Galliford Morgan Joint Venture on behalf of Scottish Water.

ABCO sourced and procured the all materials utilised in the project, pipe lengths with associated fittings, concrete collars/mattress and granular backfill material.

Mobilised C5 Jack-Up Barge c/w excavator, Works Tugs and support vessels to support the marine excavations, with material side cast for backfill.

Marine trench excavation in water depths ranging from 3m to 10m, using long reach excavator, with level control maintained from GPS dig system.

The designs included concrete collars as ballast for the outfall pipes, with concrete mattress placed on the shore sections to protect against scour, with commercial divers (ABCO Divers Ltd) utilised for operations.

All pipe lengths, diffuser sections, concrete mattress and clean stone were transported to site from Holy Loch by means of a transfer barge to support the marine installation.

ABCO Diver Ltd – commercial diving company, supported the installation of the diffuser section of the LSO pipeline. With diving operations in water depth ranging from 10m to 3m deep along the length of the pipeline.

Hydrographic and topographical surveys of the existing seabed and beach were completed, bathymetric survey were also utilised during the project, both pre/post sink surveys of the marine trench.

Preparation of project as-built reports and drawings, including all pipe testing results and pipe welding logs for quality control.


GMJV for Scottish Water


May 2010 – December 2010

Client Representatives

Mr Alan King, GMJV


Long Sea Outfalls

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