Corrosion on tank bottoms has been a problem for storage facilities that has led to many solutions. A common practice is to use secondary containment, or double bottom tanks as a means of ensuring that any leaks in the primary bottom would not lead to environmental contamination. These systems have been installed for several years, yet there has been little in the literature to document the effectiveness of the cathodic protection (CP) systems installed in the shallow spaces between the two bottoms. This paper describes the installation of a highly instrumented CP system on a large above ground storage tank bottom and provides data demonstrating the effectiveness of the system.