Opobo township extension: dredging, land reclamation, shore protection and canalization

Challenge

For the purpose of Opobo township extension, the River state government awarded a contract for sand search, bush clearing, de-stumping, reclamation and shore protection. The project aim was to reclaim surrounding swamps in the island. Opobo town is a typical Niger delta island community. It is surrounded by creeks and swamps. The creeks have a tidal difference of about 2,2 m. The swamp is mainly overgrown with thick river palm. The climate is characterized by torrential rainfall around June to September.

The major challenges were ingress of underground and tidal water, and mud slides occurring during the sand filling project due to low underground bearing capacity. Rainfall and management of excavated mud material was also challenging. Installation of gabions and reno mattresses in the slide area during reclamation were difficult due to underground flow of water. Finaly, work was impacted by unstable soil terrain of the reclamation areas, as well as by pedestrian and school children traffic crossing the haulage route.

Our solution

Adequate measures were put in place to avoid accidents. Temporary bund walls were made to reduce ingress of water, and the excavated mud was used to reinforce the perimeter of reclaimed area before grassing. Gabions at the toe were installed at about 2 m to 3 m from the creek edges, which improved workability and stability.

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