Table of Contents
The graphs below show the average total levels of different classes of contaminants taken as part of the licensing of different port dredges around the UK. The River Tees is responsible for a large part of the UK's disposal of contamination in UK waters, both because of the consistently elevated levels of contamination within the dredged sediment and also due to the large quantities of material dredge each year.
The average total contamination load in mg per kg for the River Tees varies from 860mg/kg to 450mg/kg within the berths and river to below 100mg/kg in the sea approaches.
Nowhere in the Mersey channels does the average total contamination load exceed 170mg/kg, or 510mg/kg in the docks.
Nowhere in the Harwich dredged areas does the average total contamination load exceed 220mg/kg.
The total PAH level in the River Tees sediment is 10x that in Harwich sediment, 4x that in Mersey Docks sediment, 20x that in River Mersey Channel and Approaches.
Looking at polycyclic aromatic hydrocarbons (PAHs), gives a sense of one of the specific threats which dredging of the River Tees presents.
River Tees
A level of 20mg/kg of total PAH is representative of the material which has been dredged from the River Tees over the last decade.
MLA/2025/00263
MLA/2015/00088
Mersey
MLA/2021/00202 - Mersey Navigation
A level of 1mg/kg of total PAH is representative of the material which has been dredged from the Mersey navigation channels.
MLA_2014_00573 - Liverpool Docks
A level of 5mg/kg of total PAH is representative of the material which has been dredged form the Liverpool docks.
Harwich
MLA/2023/00020
A level of 1.5mg/kg of total PAH is representative of the material which has been dredged from the Port of Harwich.
