The foundations consist of concrete footings and slab. These walls require rigid concrete footings below seasonal frost depth. Towers were built of numbered angle iron sections with concrete footings. For example, open-bottom corrugated steel structures are often built on concrete footings. It was constructed on spread footings and caissons. The posts stand on half-buried stones or concrete footings. The tower stood on four legs that went into the ground, with concrete footings. Supports are attached to approximately 2,000 concrete footings that average in diameter and are deep. The riprap would have filled the area left between the pier footings and the sheeting. Waterproofing an existing basement begins with excavating to the bottom sides of the footings. A mix of structural resins and hardener is injected into foundation ground beneath footings. The piles had to be built with wide footings to avoid them from collapsing. Some sections, however, have collapsed due to water erosion undermining their footings. Both these peaks are formed by millstone grit on limestone footings. Usually these are built in pairs until the outer sections may be anchored to footings.