Cefas Guideline Action Levels for the Disposal of Dredged Material

Cefas’s guideline action levels for the disposal of dredged material are not statutory contaminant concentrations for dredged material but are used as part of a weight of evidence approach to decision-making on the disposal of dredged material to sea. The action levels are presented below.

Action Level 1

Action Level 2

Contaminant /
Compound

mg/kg Dry Weight (ppm)

mg/kg Dry Weight (ppm)

Arsenic 20 100
Mercury 0.3 3
Cadmium 0.4 5
Chromium 40 400
Copper 40 400
Nickel 20 200
Lead 50 500
Zinc 130 800
Orgotins; TBT DBT MBT 0.1 1
PCB's, sum of ICES 7 0.01 none
PCB's, sum of 25 congeners 0.02 0.2
*DDT *0.001
*Dieldrin *0.005

* these levels were set in 1994

These values are used in conjunction with a range of other assessment methods, for example, bioassays, as well as historical data and knowledge regarding the dredging site, the material's physical characteristics, the disposal site characteristics and other relevant data, to make management decisions regarding the fate of dredged material.

The action levels are therefore not ‘pass/fail’ criteria but triggers for further assessment. In general, contaminant levels in dredged material below action level 1 are of no concern and are unlikely to influence the licensing decision. However, dredged material with contaminant levels above action level 2 is generally considered unsuitable for sea disposal. Dredged material with contaminant levels between action levels 1 and 2 requires further consideration and testing before a decision can be made.

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