The site of a former coking works “Carcoke” in Zeebrugge had to be remediated following widespread historical contamination over many years. Work on this complex, multi-layered project started in 2007 and is expected to be completed in 2021.
The remediation works are being executed in different contracts, some of them by DEC alone and the others in joint venture.
1. Removal of refractory stones
During the phased demolition of the former coke ovens on site, 15,000 tonnes of refractory (fireproof) stones, coming from the former blast furnaces, and rubble were released. The contract included the separation of these two fractions to recycle and reuse both materials.
An asbestos-containing residue was also conditioned and removed from the site.
2. Removal of cyanide-containing sediments and soil from a stream
In a stream crossing the Carcoke site approximately 8,000 tonnes of sediments were encountered, which were mainly contaminated with BTEX and PAH’s. DEC was awarded the removal, dewatering and the treatment of these sediments. All sediments were dredged along the river for approximately 2,000 meters.
After dewatering in the lagooning fields that were created on site, the sediments were transported to DEC’s dedicated sediment recycling centres in Zeebrugge and Zwijndrecht.
DEC was also awarded a contract to treat 5,000 tonnes of asbestos-containing cyanide wastes. The material had to be removed and handled in line with all legal procedures and adhering to the strictest safety measures.
3. Removal of contaminated soil
A benzole installation (for the recuperation of benzene) and gas washer (naphthalene-creosote) was encountered. Additionally, cyanide-containing soil was stored on site and severe soil contamination was discovered.
In these zones, soil was excavated down to 1.5 m below ground level. Approximately 45,000 tonnes of soil were excavated. The soil was severely contaminated with tar, cyanide and PAH’s and was treated on-site using DEC’s mobile thermal desorption plant.
The contaminated groundwater that was released during the excavation works was purified using DEC’s own groundwater treatment plant.
4. Remediation of the compression station
This contract also included the cleaning and demolition of the gas compression station, in which the following works were executed:
- Cleaning of underground pipes and sewages.
- Removal of the asbestos sealing of the underground pipes.
- Making the compression station asbestos free.
- Selective dismantling and demolition of the former compression station.
- Installation of a drainage and groundwater remediation installation.
- Excavation of the site down to 2 meters below ground level. A total of 20.000 tonnes of contaminated soil was then transported to DEC’s soil treatment centre GRC Brugge.
- Backfilling of the site up to ground level.
- Groundwater remediation for a period of 10 years.
5. Cleaning oven site
The former oven site was selectively excavated down to 2 m below ground level. The 80,000 tonnes of excavated soil were then stored on-site.
After sampling and depending on contamination levels, the soil was either:
- reused on-site
- removed for physical chemical treatment in DEC’s soil treatment centre GRC Kallo
- or removed for thermal treatment
6. Landfill and Stock
A groundwater remediation installation with a capacity of 50 m³ per hour is included in this contract, along with the excavation and treatment of 150,000 tonnes of contaminated soil.
Depending on contamination levels, soil is either:
- reused on-site
- treated using physical chemical soil washing in DEC’s soil treatment centre GRC Kallo
- or treated using thermal desorption