Subsea Trenching Contractor
Cable, Pipeline, Flexible
& Umbilical Trenching
Our Underwater Trenching Experience
The Executive Team at Subtrench have successfully developed or participated in the development and operation of:
- Subtrench Two hydraulic track driven, subsea cable, flexible
and umbilical trenching machine with interchangeable
trenching tools including jetting swords, chain cutter and wheel
cutter for sands, silts through to hard clays and soft to hard
- Subtrench One
hydraulic track driven, subsea pipeline and stiff flexible and umbilical trenching machine with mechanical cutters plus water jet trenching for sands and silts through to hard clays;
- Three hydraulic track driven, sub sea cable and small pipeline/ umbilical mechanical cutter trenching machines for sands, silts through to hard clays and soft to hard rock;
- Seven uni-directional and bi-directional sub sea pipeline jetting machines for sands, silts and soft to medium clays;
- A sub sea bulldozer;
- Three shallow draft pontoon trenching barges.
- Three hydraulic power pack and control modules;
- A power unit/ control cabin for operation of submersible trenching machines;
- Low and high pressure pump units, hydraulic power packs and systems, heave compensators, constant tension winch systems, low and high pressure hose reels, clump weight and pull bar systems, compressed air systems, hose bundle systems and pressure piping systems;
Our Experience with Trenching Operations (Back to TOP of PAGE)
As a result of trenching more than 1540 km on 46 pipeline and 7 cable and umbilical projects, the executive and personnel of Subtrench are able to provide a very experienced team to each project.
Past projects have included trenching shore crossings, shore approaches, near shore and deeper waters throughout the world. The work has been carried out from Barges, Pontoons and DP vessels. Soils trenched have ranged from sands and silts through soft and hard clays with low, medium and high pressure water jetting and combination mechanical cutter/ water jet systems; and also calcarinite and rock using mechanical cutters. Site conditions have ranged from mild to extreme.
Pipelines have ranged from 6 inch to 42 inch nominal size and cables from 32mm fibre optic to 210mm OD double armoured power cables. Some pipelines have been trenched to very stringent vertical out of straightness tolerances to account for upheaval buckling. Large diameter (210mm OD) power cables have been trenched to more than 3.3 meters on a single pass. Pipeline trench depths have been to 5 meters with multipass.
Q7 Wind Farm (Holland)
This project involved the successful trenching of a 210mm OD power cable from above the water line at the beach crossing out to the central monopile located 27 km offshore in 22 meter water depths. The first section from the beach crossing out to the 3.3 km point was trenched to a depth of more than 3.3 meters in a single pass. Average trenching speed achieved was 3.2 meters per minute. The remaining 23.7 km was trenched to a depth of 1.3 meters in a single pass and the average trenching speed was 10.2 meters per minute. When barge movements allowed, a 2 km section of the 1.3 meter section was trenched at an average 17.2 meters per minute. Generally sandy soils with varying degrees of compaction were encountered along the route.
Tatar Strait Pipeline Crossing (Russia)
This project involved the successful trenching of 18.5 km of 30 inch OD pipeline to a maximum trench depth of 2.5 meters in water depths ranging from 0 to 27 meters. Soils changed quite dramatically along the route. Most of the soils were very dense sands with varying degrees of compaction ranging from 5 to 14 MPa. Some small areas of soft silts and others of loose sand were also encountered. 1905 foreign objects including rocks, cobbles and wood were encountered along the route. A good trenching speed average of 1.7 meters per minute was achieved for this difficult trenching project. Only the use of mechanical cutters enabled the trenching to be successful.
Trenching Projects Prior to Establishing Subtrench (Back to TOP of PAGE)
The executive and personnel of Subtrench have been closely involved in the
trenching of 45 pipelines and 6 cables and umbilicals with a total trenching distance of more than
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