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r' <br />NPDES Permit Avvlication <br />II A 8 B <br />' The Carlton.Tunnet is the last and deepest of the series of de- <br />.~ watering tunnels drifted into the Cripple Creek Caldera to drain the <br />mines and permit mining at greater depths. The Carlton Tunnel was <br />completed in 1941 as a ,joint venture by and for the mutual benefit of the <br />mining companies in the District. The tunnel portal is et approx- <br />imately 1,000' elevation and the water discharged is by gravity flow. <br />The source of the discharge water is predominately meteoric water <br />falling within the caldera, a surface area of over ten square miles. <br />There may be a small contribution from connate water in the rocks. The <br />fractures. ,points, faults', mine workings and rock permeability in the <br />volcanic breccia of the caldera all act as conduits for tha water and <br />channel it by gravity f1o-v to the tunnel and .its discharge. The rsin- <br />eralization found in the water at the tunnel discharge is the result <br />of the dissolution of solubie minerals as the water percolates through <br />the rocks. No process waste water is in the discharge. <br />..- , <br /> <br />~..r {i043fi7 <br />