Licensed Treatment & Recycling Facility

Treatment and Disposal of Contaminated Dredgings

The Challenge

Contaminated dredgings from a busy fishing harbour had to be disposed of, following the withdrawal of the licence to dispose of these to sea. Contamination consisted mainly of anti-fouling agents Tri-butyl-tin (TBT’s) and hydrocarbons. Total volume of dredging was approximately 11,000 m3. Landfill disposal of the dredgings as they arose from the dredging process was very expensive.

The Solution

A waste management licence for a treatment facility was obtained from the regulators for the project duration and a water discharge licence granted. A specially designed storage lagoon was constructed for the dredged material, with a sump in one corner to collect the liquid run-off. This liquid run-off was treated by pumping through a series of filters and separators to reduce contaminant concentrations to acceptable levels before being discharged under licence to the sewer. The dredgings were treated on site by a process know as stabilisation, where cement is added to the material and thoroughly mixed using a specially adapted mixing unit. The stabilised materials were then transported to a landfill to be used as landfill cover.

The Benefits

Benefit 1

Result 1

The client was able to maintain the use of the busy fishing harbour during works and comply with new legislation regarding the disposal of dredgings using an economic solution.

Benefit 2

Result 2

By a process of treatment an engineered material was produced, which rather than being landfilled was used to provide much needed landfill cover for the landfill operator.

Benefit 3

Result 3

Massive savings were made by diverting the dredgings from landfill to instead be used as landfill cover.

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