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MEMORANDUM 4&
<br /> Adrian Brown
<br /> with a discharge estimated at from 2,000 to 2,100 gallons a minute. The tunnel maintained this flow for
<br /> over a year, becoming dry in 1898(Lindgren and Ransome, 1906)
<br /> 2. Standard Tunnel. The Standard tunnel, begun in January, 1896, has its portal in the granite west of
<br /> Beacon Hill, at an elevation of 9,027 feet. Its objective was the phonolite plug of Beacon Hill [southwest
<br /> of the main diatreme]. In February, 1896, the tunnel cut the El Paso vein, whence issued a flow of 250
<br /> gallons a minute. The water became more abundant as the contact between the granite and phonolite
<br /> was approached, and in 1898, when the phonolite was reached, the flow amounted to 1,000 gallons a
<br /> minute. This rapidly increased as the tunnel penetrated the phonolite and in 1899 the maximum flow of
<br /> from 12,000 to 18,000 gallons a minute was attained. Work was finally abandoned in June, 1899, when
<br /> the tunnel had been driven 2,800 feet. By the end of 1901 the tunnel was dry (Lindgren and Ransome,
<br /> 1906).
<br /> 3. El Paso Tunnel. The El Paso Tunnel was driven in 1903 from a portal elevation of 8,783 feet from the
<br /> south of the city of Cripple Creek to the north-east, and is approximately one mile long. Flow from the
<br /> tunnel was initially as much as 7,000 gpm, reducing to less than 2,000 gpm by 1906. Flow from the
<br /> tunnel ceased when tunnels at lower elevations reduced the water level in the Diatreme below the
<br /> elevation of the tunnel. As was the case with the Standard tunnel, the El Paso slowly lowered the water
<br /> in the Mary McKinney and Elkton mines, showing that there is a connection through open fissures
<br /> between the Beacon Hill phonolite and the main volcanic neck(Lindgren and Ransome, 1906).
<br /> 4. Roosevelt Tunnel. The Roosevelt Tunnel was driven between 1910 and 1917 from a portal located
<br /> southwest of the town of Cripple Creek, at an elevation of 8,100 feet (Sheldon, 1915). The tunnel was
<br /> ultimately driven 4.6 miles, reaching into the heart of the District. Flow from the portal rose to nearly
<br /> 9,000 gpm by 1917, dropping back by the end of that year to about 4,000 gpm (Henderson, 1926). Flow
<br /> from this tunnel largely ceased when the Carlton Tunnel was installed at a lower elevation.
<br /> 5. Carlton Tunnel. The Carlton Tunnel was driven in 1939-1942 from a portal elevation of 6,890 feet, with
<br /> the portal located immediately downstream of the confluence of Cripple Creek with Four Mile Creek
<br /> (Vivian, 1940). The tunnel was ultimately driven approximately 6 miles and enters the southern portion
<br /> of the diatreme. Flow from the tunnel was minimal in the Precambrian and Tertiary volcanics, causing
<br /> the tunnel to be connected by blasting with the Portland No. 2. Shaft,whereupon a flow estimated to be
<br /> 125,000 gpm occurred. This flow reduced rapidly to its then-normal flow rate of 7,000 gpm (Vivian,
<br /> 1941).The flow in recent decades has been approximately 1,600 gpm, and appears to be at approximate
<br /> steady state (ABC, 2015).
<br /> A number of determinations of the groundwater elevation in the period since drainage was initiated have been
<br /> made which are presented in Plate 12 and are summarized below:
<br /> 1. The water level in the Cameron Mine, located in Grassy Valley, was measured in 1972 at an elevation of
<br /> "about 9,400 feet" (Hamm, 1972).This elevation is somewhat below the level of the top of the
<br /> Precambrian rock in this area (9,500 ft amsl). It seems unlikely that this level has changed significantly
<br /> since 1972.
<br /> 2. The water level in the Carlton Tunnel is 6985 ft amsl,the elevation of the tunnel itself.
<br /> 3. A total of 44 wells and vertical piezometer strings have been installed in and adjacent to the diatreme,
<br /> principally for permitting,with the results presented in the permitting documents (ABC, 2015).The
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<br /> 130 W.4rh Ave., Denver CO 80223
<br /> 303-698-9080 www.abch2o.com
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