Let the Trenchers Trench

Over the past few years in my capacity as a client representative or OM on cable trenching projects, I have noticed a worrying trend creeping in, especially in the power cable market.

At first, it appeared in the guise of ‘reasonable endeavours’, however, this has now slowly evolved into taking control and, to some extent, responsibility away from trencher operators.

A ‘Reasonable Endeavours’ clause can be extremely useful on trenching projects, both in lump sum and day-rate operations. Depending on which, it either protects the trenching company or the purchasing company paying the day-rate as long as it is implemented with a decent dose of common sense.

The reasonable endeavours clause sets certain parameters over the minimum and maximum trenching speeds, and the steps that should be followed to change tool depth in steps to ensure the best chance of reaching target depths of burial within reasonable time-frames.

All fine as long as the procedures are clear and followed with good intent. However, what I have noticed creeping into trenching operations; and this goes for jetting, rock wheels and chain cutting, is that the trencher operators are now routinely asking for permission to increase or decrease the burial tool depth.

Plough operations don’t really come into this discussion as they have a whole different set of consequences should the plough not be adjusted in a timely manner for any changes in conditions.

The trend started a few years ago when I was working as OM on a well-known large OWF Project in the SE of the UK. The main client was under pressure to pick-things up after several issues with the project and, in my opinion, became a bit over-zealous in the control of some operations and trenching just happened to be the one I was involved in.

I am an ex-trencher and ROV operator myself with approx. 25-years of experience, ranging from Scarab 1 with 35hp of jetting power to modern high power with over 1100hp of jetting power. When I was operating a trencher along a cable, pipeline, flow-line or whatever, then the tool would be at the desired depth, optimizing the sword angle to suit the nozzle configuration set and I would probably have the trims set for a reasonable trenching speed dependent on seabed conditions.

If the vehicle speed began to slow due to the clay content of the soil increasing then I would try a bit more forward trim, or if the speed fell below the minimum then I would raise the sword depth slightly until an acceptable speed was again reached. Occasionally then I would try to get the swords back down to the original desired depth and check on the speed again.

If the vehicle stopped due to a sub-seabed obstruction, such as a boulder or a rock, then the swords would be raised gradually until the vehicle could move forward again with the swords above the obstruction, or having successfully fluidized the area around the rock that the rock has sunk deeper into the seabed. The trencher would then continue on its way and the swords would be redeployed gradually to the original trenching depth.

At the risk of sounding too cocky, it became intuitive to trencher operators. To other ROV pilots we had the easiest job in the industry; always on or near the seabed, driving in straight lines, no crane hooks, structures to work about etc. they called us ‘ditch-diggers’ out of jealousy ;)

Introducing a reasonable endeavours clause can introduce a time element to the operation, where a jetting tool or a chain cutter would have to wait a set time of maybe 5-mins before raising the tool in prescribed steps of maybe 5 or 10cm. 

Again, this is fine if applied with common sense. It ensures that the trenching operator doesn’t have to spend excessive time and tool wear moving past obstructions and ensures that the Company receives a reasonable effort to maintain the maximum depth of trench.

However, it doesn’t stop here. What appears to be happening more and more now is that trencher operators are now asking permission to raise the tool, the intuition and trust in the pilot’s intuition have gone. They need permission to change the tool depth.

In practical terms what happens is that the trencher slows due to a change in the soil conditions, or stops due to a sub-seabed obstruction and now instead of managing the issue intuitively as described before, the trencher operator has to seek permission on the comms to raise the tool, generally a call to the Bridge Supervisor who in turn has to make a call to the client. 

By the time all these permissions have been agreed, it is not uncommon to find the trencher stuck in a large fluidized hole of its own making with the cable in suspension inside a ‘crater.’

I also feel that it is creeping into the normal way of working where I have heard trenching pilots asking permission to move the tool every time it is required, with or without best endeavours clauses or instruction to do so by the client.

This also begs the question of responsibility. Is it the case that operators don’t want the responsibility for the operation of their own equipment? They instead want the pilot to guide them and therefore take responsibility for the results?

From a trenching contractor point of view, this could be good on the face of it. If every instruction from the client is recorded, or if the agreed procedures call for the client to give permission to raise the tool, then the client may also be responsible to a certain extent for the results? The client may as well be in the pilot chair for the trenching.

Surely the client has contracted the trenching company for several reasons, namely the track record of their equipment and the trenching experience of their personnel? Who knows the capabilities of the equipment better than the guys who set it up, maintain it and operate it?

As the client, you trusted them enough to give them the contract, now let them show what they can do.

In summary, leave the trenching to the trenchers. Judge them on performance and results. Ensure that they use all the tools available to them, including that very expensively acquired geology report.

Ask for justification on the set-up of the tool; the nozzle configuration for a jetting tool, teeth type and configuration on a rock-wheel, the chain type and speed of a chain cutter, stall and push-back pressures.

If something isn’t working and the results don’t look good, then ask the operators why and ask for suggested changes. Better still they will come to you first and make suggestions!

But don’t please, take the majority of the responsibility away from the operators. It’s how the tools and the people evolve.