SubTropolis is one of eight underground storage facilities in the Kansas City area, and is home to offices and storage for 55 businesses. It consists of a staggering 4.5 square kilometres of leased space, including warehouses, light industry space, offices, a network of several kilometres of rail lines and about 11 kilometres of paved and lit roads. Each street is named after a geological rock layer.
Among the huge array of goods stored in this labyrinthine complex are coffee beans, rare movie reels and, thanks to the constantly dry atmosphere due to the low permeability of the layers of shale above, millions of postage stamps stored by the United States Postal Service.
SubTropolis extends as far as 49 metres underground at its deepest. Its ceilings are 4.9 metres high and the facility includes spaces that extend for up to 12 meters, separated and supported by 7.6 metre pillars.
The facility was created using the space left behind by an enormous limestone mining operation by Huntington Midwest. The operation used the “room and pillar” mining method, in which mined material is extracted across a horizontal space, leaving behind a horizontal array of “rooms” and pillars.
Advantages of underground storage
The potential for using the mines as storage space was first recognised in the 1960s, shortly before the 1970 US energy crisis hit. People began to realize the cost and energy-related advantages of underground storage. Thanks to the 40 or more metres of rock between SubTropolis and the surface, there’s little need for winter warming and summer cooling. This reduces costs for businesses, as well as reducing the facility’s overall carbon footprint. This is significant if you consider that more energy is now used in the United Stages to heat and cool buildings than to power cars and light trucks.
The facility’s environmental impact is also minimized because no extra material, like steel or aluminium, is needed to ensure the facility’s structural integrity – the lime pillars left behind by mining operations do this alone.
One company that makes use of the Subtropolis facility is Vanguard Packaging, whose aim is to reduce its carbon footprint to zero. It doesn’t require heating or cooling for its extensive office space, and plans to use wind turbines on the surface to produce all the energy it needs “down under”.
The future of SubTropolis
As the mining operation in SubTropolis continues, the storage space it includes grows at a rate of 13,000 square metres each year. Currently there are approximately 10,000 limestone pillars laid out in a grid format, 40 feet apart. Thanks to SubTropolis and other operations like it, over 10% of industrial space in Kansas City is underground. This is an area bigger than the city’s downtown business district.