The Brookfield Zoo's Seven Seas Complex outside of Chicago, completed in May 1987, consists of an enclosed 45,000 sq ft dolphinarium, an outdoor seascale for seals, sea lions and walruses and a life support building that produces sea water. To provide a corrosion-free home for the dolphins, a team of marine scientists from the Brookfield Zoo assisted architects and engineers from the Austin Co. of Des Plaines, Ill. with the design. The team considered a number of designs and settled on a fabricated superstructure made of steel with welded portal frames of closed box sections. Requiring no interior columns, the structure blends into the space, at the same time minimizing the surface area. With fewer members exposed to the air, the potential for corrosion, a major concern given the salt, chlorine, ozone and other trace chemicals contained in the man-made sea water in the dolphin pools, is reduced.