When evaluating the ecological risks of dredging contaminated sediment at Falmouth Docks, the disaster on the River Tees serves as an indispensable cautionary tale. However, drawing meaningful lessons for our regulators and local stakeholders requires getting the chronology, dredging operations, and legal facts precise.

The Site: Development of the heavily contaminated South Tees site on the river's south bank—historically home to coking works, ironworks, and heavy chemical manufacturing—contained over 8,000 tonnes of coal tar and toxic byproducts.

COMAH Classification: Work on the site began in 2019 and accelerated rapidly in Autumn 2021. Because of the extreme threat that coal tar and mobile polycyclic aromatic hydrocarbons (PAHs) pose to the aquatic environment, the site was classified as an upper-tier COMAH (Control of Major Accident Hazards) facility.

Public debate frequently confuses the mass crustacean mortality with later capital dredging. The timeline demonstrates that the catastrophic crab die-off in September / October 2021 occurred during an intense maintenance dredge window, not the later Freeport capital dredge:

In Autumn 2021, an intensive 10-day dredging campaign targeted a 1 km stretch of the River Tees navigation channel.

Over just 10 days, this operation extracted roughly 18% of the entire annual dredged volume for the Tees—releasing over 50,000 tonnes of fine, highly contaminated sediment into the littoral flow.

Because this specific stretch was more contaminated with PAHs than previously dredged material, the rapid mobilisation of fine sediment is the primary factor linked to the devastating mass mortality of crabs along the coast.

The massive capital dredge to create the South Bank Quay for the Freeport did not cause the initial Autumn 2021 die-off.

Capital dredging for the deep-water quay occurred considerably after the crab die-off, in 2022 and 2023.

While the capital dredge represented a massive volumetric intervention, the Teesside disaster demonstrates that intense, concentrated dredging of toxic sediment even under routine channel maintenance regimes can precipitate an immediate marine ecosystem collapse.

A landmark Judicial Review of the Marine Management Organisation's (MMO) 10-year maintenance dredge licence for the Tees challenged the poor consideration of environmental risks:

The Outcome: The Judicial Review resulted in the quashing of the 10-year maintenance licence.

What the MMO Admitted: The MMO only conceded on one specific, critical regulatory failure: they had failed to properly delineate the areas which were too contaminated to be dredged.

The Significance for Falmouth: The other environmental and sampling issues raised in the challenge were not accepted by the MMO. This makes spatial delineation of toxic hotspots the primary regulatory battlefield. If dockyard basins contain hot spots of legacy industrial contaminants, licensing bodies cannot rely on broad average dilution—they must explicitly delineate and embargo contaminated zones from being dredged or dispersed into the water column.

Whether an operation is classified as a “capital dredge,” “pocket dredge,” or “routine maintenance,” the physical and chemical risks remain clear: excavating fine estuarine sediments laden with legacy chemical contaminants releases them directly into the water column.

In Falmouth's semi-enclosed ria, where incoming tides carry suspended particulates directly toward protected maerl beds and wild native oyster beds, the MMO cannot repeat the regulatory failure of Teesside. Any attempt to dredge Falmouth Docks without strictly identifying and isolating contaminated zones poses a severe, unacceptable risk to the marine environment.