Posted on March 10, 2026
By David Kinlan
One of the most persistent sources of dispute on dredging projects arises when a Contractor encounters materially different seabed conditions and productivity falls below its tender assumptions.
The sequence and steps usually taken are familiar to those in the industry:
1️⃣ Production drops
2️⃣ The Contractor investigates the cause
3️⃣ Differing ground conditions are identified
4️⃣ A claim for loss of productivity is raised
But the contractual success of that claim rarely depends on the ground conditions alone.
It usually depends on process and records.
Common issues that arise
Across marine infrastructure projects and throughout my career as a Contractor Contract Manager I was repeatedly faced with the same problems:
1. Late notification
Under most forms of contract:
- FIDIC 1999 – Clause 20.1
- FIDIC 2017 – Clause 20.2.1
- NEC4 – Clause 61.3
the Contractor must notify within a defined period (often 28 days).
Production in dredging is never a constant, it may rise or fall. Variance is to be expected.
By the time a ‘significant’ production issue is clearly identified & diagnosed and the contracts manager is advised with enough details to prepare a notice, that notification window may already be closing or closed entirely.
Failure to notify in time will inevitably result in a time bar, meaning the contractual entitlement disappears even if the ground conditions were genuinely unforeseen.
This has happened more often than I care to count!
2. Difficulty proving the baseline productivity
To demonstrate loss of productivity the Contractor must prove:
- Expected production rates (not just an average)
- Actual achieved production (good & bad)
- The causal link between the two
Tender assumptions as to the likely range in anticipated production are often poorly documented, particularly where production estimates were derived from internal fleet models.
The biggest obstacle I often faced preparing a claim was showing the causal link.
3. Ground model vs reality
Dredging projects are notorious for insufficient site investigation data:
- Widely spaced boreholes;
- soil samples of limited reliability;
- Geophysical interpretation errors
When the dredger starts its operation, reality often diverges from the production estimators interpretative assessment.
Remember Obrascon & Van Oord court cases have shown the Contractor must ‘reasonably’ interpret between sampling locations and the test is what an experienced contractor would have deemed reasonable (that word again!) to expect.
4. Weak daily records still plague the industry
This is where dredging differs markedly from conventional civil engineering.
On a road or bridge project the daily record might include:
- labour numbers
- plant hours
- weather
- activities performed
But dredging claims demand a far more technical record set.
The records that actually matter on dredging projects
To demonstrate a productivity loss caused by ground conditions, daily records typically need to include:
- Dredge production logs (m³ per hour/day)
- Pump pressure and cutter power curves (data measured on board)
- Mixture density and flow rate (data measured on board)
- Overflow losses (TSHD operations)
- Cycle time analysis (TSHD loading/sailing/discharge)
- Dredge position logs (DGPS)
- Physical samples recovered at the cutter head or at the discharge point • Block or grid production mapping
- Weather and sea state records
- Downtime categorisation (equipment maintenance & repairs, bunkering, etc)
Modern dredges record much (but not all) of this automatically through vessel monitoring systems.
But unless that data is properly extracted and preserved, it often cannot be used effectively in a claim lodged within the short timeframes allowed in the Contract.
If the Contractor only provides overall daily production, the Employer often argues:
- inefficiency of the dredger (wrong vessel selected?)
- operator poor performance
- weather & sea state interruptions (contractor risk)
- equipment problems, breakdown, etc
However, grid-based production data allows the Contractor to show:
- productivity before entering difficult ground
- productivity within the difficult ground
- productivity after leaving the area
This spatial correlation is powerful evidence.
A recurring lesson
In dredging disputes, the debate rarely centres on whether the ground was difficult or not.
That evidential aspect can sometimes be the easy part.
Instead the dispute becomes focussed on:
- Was the condition unforeseeable?
- Was timely notice given?
- Can the Contractor show the causal link & prove the productivity loss with reliable records?
Without those elements, even a technically valid claim will, and often do, fail.
Ground risk is the oldest problem in dredging
When I started in the industry I remarked to my then boss that dredging is somewhat unique in that in the actual process you are destroying your claim evidence!
I came from civils background and I was used to the situation if you hit rock you stopped the excavator, visually inspected, took photos, measured & collected the evidence and informed the Employer/Engineer. Not so simple with dredging.
You therefore have to rely on collecting often what may be considered as circumstantial evidence.
Contractors are advised to present this evidence in a claim as a GIS heat map, showing:
- red zones → low production
- green zones → normal production
- yellow zones → higher production
- overlay of boreholes, geophysical and CPT data
This allows arbitrators or dispute adjudicators to visually see:
· where the ground model failed to show the differing condition;
· where productivity dropped; and
· the spatial relationship between the two.
In large infrastructure and dredging projects, claims often continue to be fought over years after the events occurred.
Without original source records fed into any analysis it becomes extremely difficult to establish:
- cause and effect
- actual productivity vs planned productivity
- responsibility for delay or disruption
