The National Institute of Ocean Technology (NIOT) is planning to launch the steel caisson (submerged structure to reduce wave activity) into the sea by August 20 as part of the beach nourishment project.
The construction of the offshore artificial reef in front of the Chief Secretariat as part of the project is in final stages.
About 70% of the work has been completed. NIOT has speeded up the work on the construction of the reef base.
However, a large quantity of sand had accumulated around the working platform where the steel caisson is to be lowered into the sea.
“NIOT is getting the sand dredged with the help of two drag flow pumps to facilitate the completion of the reef base and launching and positioning of steel wedge or caisson on it. The construction of the reef base will be completed by the first week of August,” said M.V. Ramana Murthy, project director of NIOT.
The steel caisson will be 50 metres wide and 60 metres long with an elevation of 2.5 metres. The caisson will be filled with water or sand. The steel plates each will have a thickness of 25 mm.
Mr. Murthy said the main objective of the project is to demonstrate how the beach could be restored naturally without disturbing the ecosystem.
The caisson has to be positioned around 4.5 metres below the sea level.
It weighs about 900 tonnes and NIOT has planned to set up a winch system on the shore to launch and position the caisson/steel wedge reef on the reef base.
A winch system on the shore and a multi-sleeve system will be used for the launching and positioning of the caisson.
It will be given anti-corrosive coating and positioned on the reef base.
Free movement
The submerged structure will reduce wave activity and allow sand to freely move towards the north and prevent erosion along the coastline.
According to the project, two submerged reefs will be built at a distance of 125 m from the sea near the Chief Secretariat and the south of the new pier.
The reef near the Chief Secretariat will be funded by NIOT at ₹25 crore, while the second reef will be funded by the Puducherry government.
The submerged structure will reduce wave activity and allow sand to freely move towards the north and prevent erosion along the coastline.
Once the steel caisson is lowered into the sea, about 70% of the sand will be bypassed to the north in the first year followed by 100% from the next year.
As per a NIOT report, 0.3 million cubic metres of sand will be required for the beach nourishment and the sand dredged from favour mouth will be put on the seawall along the promenade beach.
Over the last several years, the beach has been hit by erosion and nourishment will result in restoration of sand level.
