Retention/Detention Ponds are often added to a site-design to mitigate storm-water runoff. Enhanced Porosity Concrete (EPC), aka Pervious Concrete, can be used as a parking-lot pavement that allows storm-water to flow through it. If a detention-pond was covered with a filter-fabric, and clean-gravel was used to fill the pond on top of the filter-fabric, then EPC could be used to cover the gravel such that a parking-lot would be created on top of the pond, and using the same foot-print as the pond. The gravel would support the pavement loads and the water-storage capacity of the gravel-filled pond would be a function of the amount of void-space in the gravel.
Because parking-lots and detention-ponds both take up a large part of land area of a building-site it would seem that combining the two in the same foot-print would save money and land area for the building-site developer. The pavement would also keep debris out of the pond and create a safer environment.