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<br />IN REPLY REFER TO:
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<br />INFOR}~TION FOR THE PRESS
<br />
<br />SUBJECT: Quantity and Quality of Drainage from the Argo Tunnel and
<br />Other Sources Related to }letal Mining in Gilpin, Clear Creek,
<br />and Park Counties, Colorado
<br />
<br />RELEASE DATE: Immediately
<br />
<br />FOR }~DITIONAL INFOfu~TION CONTACT:
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<br />i.,,,D 2;",'fE!f$l'f???rJ~' --,
<br />; f!(-LL~J-1:1 r c;v!fJ1
<br />'i [fe T' , ,n
<br />!'t::-~~_ Z 5 1917;JJ!J1lI
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<br />RVAliON
<br />BOARD
<br />
<br />According to a recent U.S. Geological Survey, Department of the Interior report,
<br />18 metal-mine drainage sources have been located >vithin the Hissouri River
<br />basin in Gilpin, Clear Creek, and Park Counties, Colorado. At least 13 of
<br />these sources contain high ac'idity and (or) trace-element concentrations or
<br />contribute >vater to adversely aff~cted streams. One of the major drainage
<br />sources--the Argo Tunnel in Idaho Springs--exhibited relatively constant '" ter
<br />quality during the period March 1976 to March 1977. Average total trace.-
<br />element concentrations, in micrograms per liter, were as follows: arsenic,
<br />140; cadmium, 150; copper, 5,800; iron, 180,000; lead, 100; manganese, 94,000;
<br />and zinc) 4L~, 000. Except for lead, the trace elements ,,,ere mostly dissolved
<br />(82 percent or greater) and appear to represent baseline concentrations.
<br />Spring chemical flushes containing higher than baseline trace-element concen-
<br />trations occurred in the Argo Tunnel in 1973 and 1974, but not in 1975 or
<br />1976, and probably not in 1972. The spring chemical flushes appear to be
<br />associated with increased infiltration from snov:melt in the catchment of the
<br />tunnel. Long--term degradation of >vater flowing from the Argo Tunnel is shOml
<br />by incr~ases of at least 2,5 to 8.0 times for dissolved solids, dissolved
<br />iron, calcium, magnesium, and sulfate since 1906. Acidity of the >vater has
<br />chang~d from neutral to a median pH of 2.9 in 1976-77. Management alternatives
<br />for mine'-drainage abatement are present~d and discussed in the report in
<br />regard to general applicability in the study area.
<br />
<br />J. E. Biesecker, District Chief
<br />U.S. Geological Survey, h~
<br />Colorado District; Mail Stop 415
<br />Box 25046, Denver Federal Center
<br />Lake>vood, Colorado 80225
<br />Telephone: 234-5092
<br />234-3815
<br />234-3458
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