Large diameter cylindrical welded steel tanks bearing on soft clay deposits can experience substantial settlement. Ground improvement by provision of granular piles is an effective method to strengthen the soft clay and control settlements within acceptable limits. The paper presents the installation technique together with results of load tests conducted on trial granular piles to assess the behavior of the improved ground. The tank performance, evaluated by hydro-testing the tank, compared well with the theoretical model used to compute the settlement of the improved ground.