Economics And Development Of Shallow Mine Space

An acceptable source of concrete aggregate is available in Kansas City in a continuous, medium bedded, slightly dipping limestone unit. Removal is accomplished in shallow depth, 12 feet to 17 feet high, room and pillar mines. The accepted empirical design spaces 20 foot pillars 60 feet on center. A portion of the 20 foot unit is left in place for roof support. Rock and soil cover is variable to 100± feet maximum. Long-term stability of these mines is affected by numerous factors, including the above mine-rock profile, ground water conditions and mining practice. Crusher-run aggregate sells at the mine for $2.20 per ton, yielding a gross income of $2.00 to $2.80 per square foot of mine. Use of mine space for real estate development requires a new perspective in mine development. Mining practices to obtain long term stabile structures can become an over-riding factor as compared with minimum production costs and maximum extraction ratios. Poorly mined areas are unusuable for secondary purposes. Development cost for lease space in less desirable mines is substantially greater than those planned for a secondary use. Real estate development in mine space involves unique engineering problems. Properly engineered developments offer singular advantages. Warehouse lease space sells for $.50 to $1.00 per square foot per year; fully developed office areas may double these values.