WHEN clay soils were too compressible to support typical storage tank foundations for a tank farm in Houston, Texas, Geopier Foundation Company-Houston Inc was selected to install its foundation support piers. The project was discussed during the Independent Liquid Terminals Association Meeting (ILTA) June 11-14 in Houston.

Foundations must have the bearing capacity to support tanks properly so that they don't become distorted. In addition, tank roofs must be able to retain their convex shape, said Tommy Williamson, president of Geopier, Humble, Texas.

To provide a foundation that would meet the specifications for the location, Geopier constructed a reinforced granular pad foundation supported by piers filled with recycled concrete aggregate, said Williamson. For the 10-tank project, the company constructed 3,150 piers at a cost of about $550 per pier. He estimated a cost savings over other types of construction at about $400,000 to $700,000. The project was completed in six weeks.

After the piers were installed, and the foundation and tank constructed, only one inch of settlement was detected after hydro testing, he said. Williamson estimated that other types of tank foundations would have a settlement of four to seven inches.

Pads for each tank varied in thickness from 24 to 36 inches. Piers were installed by drilling holes and tamping the aggregate into the holes. The aggregate is composed of recycled concrete in sizes from 1½ to 4½ inches in diameter.

There is little disturbance from the tamping and no excess soil to haul away, he said. Few supplies are needed for the project.

“All that you do is stockpile a few loads of aggregate and begin work,” he said.