The WTC memorial fountains occupy the exact same footprint where the twin towers stood, roughly 70,000 Sq Ft (6,500 Sq Meters) both fountains combined. Underneath these fountains exist occupied space in the form of mechanical equipment rooms to the handle water and filtration systems. We have heavily steel reinforced structural cast-in-place concrete slabs to which was applied a vapor impermeable, fluid applied, polyurethane waterproofing membrane. Over this membrane, there were 2' by 2' concrete pedestal pavers placed that were made in a custom color to match the black polished granite walls of the fountain. These pedestal pavers have ½" thickened edges that provide support when placed on the membrane system. This ½" annular space therefore will hold water under the pavers whenever the fountain is drained for cleaning or any other purpose.

The problem was that after the pavers were installed and the fountains were filled with water to an operating depth of 18" over the paver surface, the color contrast between the granite walls and the pavers was architecturally dreadful. At that time I received a call from the waterproofing sub-contractor which was KJC Waterproofing out of New Jersey with the question "what can we do, the architects are not happy and the pavers need to be black". The challenge was that another vapor impermeable product could not be used, and "breathability" of the concrete pavers needed to be maintained. My recommendation was Miracote MPC with the liquid catalyst factory tinted in black, and applied in two coats for a total of approximately 62 mils. After a 2 day cure, we recommended to seal the MPC with Miracote Drylook Sealer (fluorocarbon-modified siloxane water repellent) for enhanced water penetration resistance. We then required a 3-day cure prior to filling the fountain with water.

Only the pavers were done....not the walls as those were made up of polished granite. That same granite was considered to replace the pavers, but the cost would have been enormous. There were some other products considered, such as pool coatings, but MPC/Drylook Sealer system was chosen due to its vapor permeability benefit. Samples of products under consideration were applied and submerged in water for an extended period of time for evaluation, and MPC came out on top due to function, ease of application, short time period prior to exposure to full emersion and material cost.