Loch Ryan WWTW LSO


ABCO Marine Ltd were contracted by Leslie MWH JV as specialist marine contractor on Loch Ryan WWTW Long Sea Outfall Project for Scottish Water. We supplied a design and build package, from Site Investigation to obtain outfall route, detailed works design with associated pipe ballast and protection, diffuser section design and construction.

We supplied and prepared the outfall pipe lengths in Larne, N Ireland, with the pipe welding into two lengths with all pre-cast concrete collars attached and secured. The two pipe lengths were connected into one continuous string and all hydrostatic testing was completed prior to marine tow. The prepared pipe string was towed from Larne Harbour 25 nautical miles to site, and sunk into the excavated marine trench using the ‘float and sink’ method of pipe installation.

Project Information

560mm Outside Diameter Pipe and associated diffuser fittings were placed from Ch-0+005 on shore to ‘Low Water Mark’ (LWM) to the diffuser outlet point at Ch0+656.

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

Mobilised two C5 Jack-Up Barges c/w excavator, Tug and support vessels to support the marine excavations through boulder clay, with material side cast for backfill. Excavation of trench in 15m deep water, using long reach excavator, with level control maintained from GPS dig system.

Pipe length was prepared in Larne, with all pipe welding, concrete collaring and connections completed on site. Pipe was hydrostatically tested in Larne, with all results recorded and witnessed by the client. 25 nautical mile marine tow of prepared pipe string, before ‘float and sink’ installation of pipe into prepared marine trench.

Trench backfill incorporated, pre-cast concrete kennels on the shore section along with 1000t of imported Rock Armour. 300 number concrete kennels were placed over the entire length of the outfall pipe to protect the pipe and provide additional ballast weight.

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

ABCO Divers Ltd – commercial diving company, supported installation of the diffuser section of the LSO pipeline. With diving operations in water depth of 15m deep, with dive spread mounted on C59 Emotion Jack-Up barge.


Leslie MWH JV for Scottish Water


January 2012 – June 2013

Client Representatives

Mr Carl Tidy, Leslie MWH JV


Long Sea Outfalls

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