With the government's thrust on reduction of emissions from coal-based thermal power plants, installation of Flue Gas Desulphurisation (FGD) system in the existing and upcoming thermal power plants has become the norm.

CENGRS has successfully completed the Geotechnical & Topographical Survey Work for Flue Gas Desulphurization (FGD) for 3 x 500 MW Vallur Thermal Power station Tamil Nadu on behalf of Tata Projects Limited. NTECL is the owner.

The site is close to the Arabian Sea. Shallow water table, potential for liquefaction of loose sands during earthquake and high salinity were the challenges.

In addition to boreholes, static cone penetration tests and cross-hole seismic tests were performed to assess liquefaction potential.

As per our analysis, even though the site is located in Earthquake Zone III as per IS: 1893-2016, liquefaction is expected to 8.5 m depth in the Chimney area and to 10 m depth at the location of the Absorbers. Foundations for the Chimney, Absorber and other critical heavily loaded facilities were placed on RCC bored cast-in-situ piles. Ground improvement was done for the medium loaded facilites.

The high chloride content in the groundwater nececitated special precautions to be taken to ensure durabillity of foundation concrete.