Clay Tailings Impoundment

Three independent heavy earthwork contractors worked two years to complete construction of the largest phosphate beneficiation byproduct clay tailings impoundment in Central Florida. When filled to design capacity, the 754-acre impoundment will contain 54,000 acre-feet of phosphatic clay tailings and water at a maximum depth of 90 feet. Completed in June 2011, the approximately 4.8-mile long perimeter embankment dam and internal baffle wall were constructed on previously mined land with engineered fill comprised of 12.5 million cubic yards of overburden soils borrowed from spoil piles set aside during strip-mining. The overburden soil fill was augmented with 7 million cubic yards of hydraulically-placed sand tailings. The perimeter dam has a minimum crest elevation of 154 feet above National Geodetic Vertical Datum of 1929 (NGVD) which provides a water level freeboard sufficient for managing water generated from 39 inches of precipitation in a 24-hour period falling on the catchment area. Ardaman & Associates, Inc. provided the engineering design, construction plans and specifications, and quality control inspection and testing during construction.