Profile: Steel Tank Institute & Steel Plate Fabricators Association (STI/SPFA) serve the water, food, petroleum and chemical markets. We build steel pressure vessels. Water tanks are built in many styles and decorative color schemes, including elevated, reservoir, standpipe and other designs. Steel atmospheric tanks in underground (UST) and aboveground (AST) designs store petroleum and hazardous liquids. Underground steel tank designs include the cathodically protected tank, composite steel and fiberglass tank, urethane composite and fiberglass jacketed steel dual wall tank as well as oil water separator.