|
<br />Artificial Recharge of Ground Water in Colorado
<br />A Statewide Assessment
<br />
<br />Additional Considerations
<br />Significant costs would be incurred to seal the mines to maintain hydraulic control of injected
<br />water. Most metal-mining districts are in steep, mountainous terrain deeply dissected by
<br />streams, Mines in these areas are primarily accessed through adits (horizontal workings that
<br />intersect the land surface), Each mine of this type would need one or more engineered plugs,
<br />depending on the number of adits, to limit water drainage out of the workings, The cost of
<br />engineered plugging of an adit is site specific, but ranges from approximately $] 00,000 to
<br />$300,000 (Larry Perino, Sunnyside Mine, oral commun" 2003), Therefore, if normally more
<br />than I 0 individual mines make up a mining district, construction costs to store the amount of
<br />water identified in Table Vll-3 would be $1,000,000 at a minimum and possibly several times.
<br />higher. Also, this cost does not include the infrastructure to bring source water to the site and to
<br />retrieve and distribute stored water.
<br />
<br />Mine workings often intersect subsurface faults and fractures that commonly extend to the
<br />ground surface, These can serve as additional conduits to drain water out of the mine, ]n most
<br />situations, a metal (hardrock) mine will be a leaky storage vesseL Leakage of stored water from
<br />the mine will likely cause impacts outside of the project area that are difficult to predict
<br />
<br />Natural Caves
<br />
<br />Like abandoned mines, natural cave systems represent subsurface void space that may be
<br />suitable for underground water storage, Colorado contains a few hundred caves scattered
<br />throughout the mountainous western part of the state (Figure VII-6), Many of Colorado's caves
<br />are found in the Mississippian Leadville Limestone, but they also occur in the Manitou, Fremont,
<br />Minturn, and Honaker Trail formations, Most of these caves are small with less than 100 feet of
<br />passage, However, there are concentrations of longer caves in the White River Plateau (Garfield
<br />County), Lime Creek Wilderness (Eagle County), Sangre de Cristo Mountains (Custer County),
<br />and in Williams Canyon (El Paso County), Colorado reportedly has only ]2 caves with passages
<br />greater than one mile in length (Rhinehart, 2003). Of these, seven are on public land managed
<br />by the USDA Forest Service, one is within land managed by the Bureau of Land Management,
<br />and the other four are on privately-owned parcels,
<br />
<br />Published information on caves and karst in Colorado is sparse, with only three books
<br />specifically written about caves in the state, The most comprehensive publication about caves is
<br />the quarterly journal Rocky Mountain Caving, edited by Richard Rhinehart. This journal
<br />provides historical, scientific, and anecdotal information on caves, but specifically avoids
<br />publication of cave locations. Because caves are fragile, non-renewable resources, people within
<br />the cave exploration and scientific communities have learned that secrecy is the best protection,
<br />and location information is closely guarded, Caves on public land became officially protected
<br />with the passage ofthe Federal Cave Protection Act of ]988, The purposes of this Act are to
<br />secure, protect, and preserve significant caves on Federal lands for the perpetual use, enjoyment,
<br />and benefit of all people, and to foster increased cooperation and exchange of information
<br />between governmental authorities and those who use caves located on federal lands for scientific,
<br />educational, or recreational purposes,
<br />
<br />68
<br />
|