Precast concrete secondary containments for aboveground storage tanks containing petroleum products; a simplified design approach

Abstract

Secondary containments are installed surrounding aboveground storage tanks containing petroleum products to prevent soil, groundwater and surface water contamination in the event of a leak or to prevent spread of fire to adjacent properties in the event of a fire. Requirements for secondary containments are strictly regulated through industry standards and guidelines developed by environmental regulatory authorities of federal and provincial/state governments across North America. Earthen dykes containing impermeable layer/liner are often installed surrounding large storage tanks to provide secondary containment. Desired containment volume is achieved by increasing the area of containment or the height of dyke or both. Earthen dykes can be expensive to maintain and clean in the event of a leak. Earthen dykes require considerably more real estate than dykes built using concrete walls supported by a system of lateral bracings. Concrete dykes can be a cost effective alternate solution when compared with the lifecycle cost of earthen dykes. The economic design can be achieved by optimizing dyke wall thickness and/or lateral support spacing. Slenderness and crack control are critical design parameters for an optimized design. Hence the design of optimized concrete dykes is governed by displacement criteria. The mid-span lateral displacement due to hydrostatic pressure can be controlled by embedding a weaker steel member at the top of the concrete wall panel and a stronger steel member at the bottom of the concrete wall panel that is designed to allow uniform mid-span lateral displacement across the wall. Strength of the wall panel is calculated by enforcing displacement compatibility of steel and concrete. This paper will outline a simplified design method for concrete dykes and discuss design parameters, methodologies, tools, and limitations. Finite element analysis will be used to validate the proposed design methodology.