A pad made of reinforced concrete, used to provide additional weight to an underground storage tank and thus prevent it from floating in event of a high water level in the excavation. 

Such pads are typically constructed in the bottom of tank excavations in high groundwater areas. The tanks, in turn, are fastened to the pads through use of connecting straps. The weight of the pad plus the weight of the backfill above the pad will help hold the tank in place.