Concrete Containment Wall vs. Earthen Containment Dikes

Abstract

The most common form of secondary containment for petroleum tanks is an earthen dike structure. Precast, pre-stressed concrete wall structures, however, can offer effective secondary containment, especially for sites that encroach on existing infrastructure, property limits, or environmentally sensitive areas. A secondary containment system constructed with concrete walls occupies a much smaller footprint than an earthen dike structure. This reduction in footprint can be critical, particularly in today’s expanding market which is placing increasing pressure on available site properties including, in many cases, the need to acquire permits for the development of environmentally sensitive areas. The new Tank #79 and Tank #80 projects at the Enbridge Griffith Terminal utilized an 880 lineal foot precast, pre-stressed concrete containment wall system. The existing site soils were sandy and unsuitable for containment berm construction. Therefore, earthen dike structure construction would have required imported clay material. However, the primary motivation for using the structural wall system at the Griffith Terminal was to reduce wetland impacts on the adjacent protected Hoosier Prairie Wetland. The concrete containment wall system saved approximately one half acre of wetland which significantly reduced wetland mitigation costs and also fulfilled the wetland permitting requirement to reduce (minimize) wetland disturbance. Finding a vendor with past experience in the fabrication of precast, pre-stressed concrete panels suitable for secondary containment was a challenge due to their limited prior use in similar containment wall systems. For the design, detailing and fabrication of this system Enbridge worked closely with precast concrete fabricators to define a typical pre-cast panel which was economical, could be easily installed, was structurally suitable for containment design forces and which would prove durable in a cold-weather environment. Additional considerations included proper sealing of adjacent wall panel joints, selecting and detailing a suitable impermeable liner to bridge the wall to the tank lot clay layer, and design and installation of supporting concrete caissons and steel piles for wall panel vertical and lateral support. The Tank #79 and #80 projects at the Griffith Terminal have benefited from the decision to depart from the traditional earthen berm and construct a structural containment wall system. These benefits included reduced wetland and overall project footprint impacts, accelerated project environmental permitting and an accelerated project construction schedule.