This paper relates Kansas City's experience in developing underground space. It focuses on the technical, legal and psychological aspects. Kansas City, Missouri, in the heart of the United States, is setting an exciting pace for the development and use of underground space. Their activities are being monitored throughout the world by those who hope to either emulate or modify and improve upon this experience. Kansas City is serving as a proving ground for underground development. Fortunately, Kansas City has a very extensive ledge of limestone located near the surface, extending as far as fifty miles in each direction. This ledge, known as Bethany Falls, outcrops in the river bottoms and is generally accessible from surface roads and highways. The quality is uniform and high in calcium carbonate making it ideal for a number of uses including agricultural lime, cement production, mineral filler, concrete and asphalt aggregate, plus many others. Mining is accomplished in a conventional manner on a room and pillar basis, leaving twenty-five foot square pillars on sixty-five foot centers.. This results in a regular geometric pillar pattern yielding approximately 85% of the underground area as open and usable which virtually doubles the size of the surface area of the property. It is as simple as driving back into the hillside from surface streets to gain access to the underground area, thus not having to change depth to go underground. Overburden averages one hundred forty feet above the mined out area. One of the main attributes of underground m1n1ng in Kansas City is that its initial purpose was to serve the aggregate rock needs of a growing industry of surface development. Great Midwest Corporation, for instance, owns 2,000 acres and has the mining rights below all of it. During the years that this corridor was being developed, they served surface construction with concrete and asphalt aggregate rock. Now that the corridor has grown to become one of the most active industrial districts in the metropolitan area, their surface property is relatively unused and is available for surface development. By mining 85% of the area from under the surface, they have nearly doubled the developable area. Instead of 2,000 surface acres, they have a combined potential of 3,500 acres that can ultimately be used. Obviously, the mineral extraction cannot all take place in an area this extensive during the few years that the area growth is taking place. Great Midwest Corporation mines about a million square feet annually which gives an adequate inventory of underground space to meet market demands for reuse for development purposes. To prepare the subsurface for mining and subsequent reuse, the hillside is excavated to expose the bluff. The mining simply extends directly into the bluff. Because the most unstable portion of the mine is generally the forward rooms closest to the bluff, experience shows that it is advisable to leave a solid rock mass of two hundred to three hundred feet thick to help eliminate structural problems.

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