Brazil has a wealth of iron ore reserves that can benefit the country’s economy and stimulate growth. To exploit these reserves German steel-maker ThyssenKrupp Steel and Brazilian mining company Companhia Vale do Rio Doce (CVRD) teamed up to construct a steel factory on the northern shore of Sepetiba Bay, an area of great natural beauty near Rio de Janeiro.

Brief

As a partner in a joint venture Boskalis was commissioned to dredge over 10 million cubic meters of material for the construction of a harbor basin and an access channel and to reclaim 200 hectares of swampland using hydraulic sandfill. The work also required Boskalis to dispose of 8 million cubic meters of clay and silt onshore and to de-water the reclamation and disposal areas.

Challenge

Boskalis approached the work with extreme care in order to meet all the environmental criteria:

  • A cutter was equipped with an innovative ecological cutter head  to remove previously contaminated soil with precision and ultra-low turbidity;
  • Deep pits were dredged to contain the contaminated soil and sealed with a capping of clean soil;
  • Selective dredging was used to reclaim the swamp area. This method took longer but ensured that disruption to the aquatic environment was kept to a minimum;
  • Waste water was conducted through a series of specially-constructed silt deposit areas in order to mitigate turbidity levels;
  • The reclaimed area was dewatered using 10 powerful water pumps with the water being fed through a pair of sinker lines and discharged four kilometers offshore. 

Solution

Boskalis approached the work with extreme care in order to meet all the environmental criteria:

  • A cutter was equipped with an innovative ecological cutter head  to remove previously contaminated soil with precision and ultra-low turbidity;
  • Deep pits were dredged to contain the contaminated soil and sealed with a capping of clean soil;
  • Selective dredging was used to reclaim the swamp area. This method took longer but ensured that disruption to the aquatic environment was kept to a minimum;
  • Waste water was conducted through a series of specially-constructed silt deposit areas in order to mitigate turbidity levels;
  • The reclaimed area was dewatered using 10 powerful water pumps with the water being fed through a pair of sinker lines and discharged four kilometers offshore. 

Result

The project was started in November 2006 and completed on schedule in early 2008. Boskalis complied with all the environmental requirements without sacrificing either speed or efficiency.

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