Gypsum is a byproduct of phosphoric acid production that is normally stored with clay in large above-ground stacks and clay ponds for extended periods of time. These stacks must be closed once they reach the end of their useful lives. Closure includes capping, re-sloping, water management and long-term care as required by law. Inactive portions of the gypsum stacks at Geismar LA are capped and managed for water impact.