The types of rock mined and the
fracture lines make many of these mines unsuitable to hold high pressure air, even
though they are significantly deep. The mountains of Colorado are heavily
fractured, and these fracture lines run at all angles to the surface, so it is likely that
most mines would have a fracture line leading directly to the surface that would
be exposed by high pressure air. There might not be a total loss of pressure, but
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the leakage could be enough that the system becomes inefficient and no longer