ENV-03-129 Secondary Containment for Above Ground Storage Tanks (ASTs) – More Than Meets the Eye

Description:

The environmental history of aboveground storage tanks (ASTs) is marked by instances of product releases. The vast majority are small subsurface1,2 releases and are therefore difficult to detect. Although no secondary containment system can economically guarantee complete containment, more stringent federal and state regulatory requirements for secondary containment are improving the overall environmental performance of ASTs. For an existing facility, these requirements include retrofitting the bottom of the AST and the secondary containment system. A project included the upgrade of secondary containment systems for a refinery in the Midwest. The refinery was originally constructed over 50 years ago. Recently, the secondary containment systems for over 40 aboveground storage tanks were upgraded to satisfy state requirements. The ASTs included single- and double-bottom tanks founded directly on granular fill. Some of the tanks included concrete ring wall foundations. The ASTs range in age from 1 to 30 years. The essential requirements for the facility are that the secondary containment system be nearly impermeable to water and that the containment volume of systems open to precipitation be 110 percent of the largest tank volume in the basin. Because the native soil at the facility has often exhibited greater permeability than allowed, secondary containment system upgrades were necessary. Although theoretically a straightforward process, upgrading or retrofitting the secondary containment systems at an operating facility produces several plant-wide impacts and potential system conflicts. To identify, evaluate, and account for these system-wide impacts, Barr and refinery staff conducted a frontend review of candidate secondary containment systems. Barr and refinery staff then selected the most appropriate systems, implemented the systems, and incorporated lessons learned during each phase of the project. Design and construction of the plant-wide secondary containment system upgrade took four years.