GENERAL46988 - Laserfiche WebLink

Home Browse Search

The current site operator is Battle Mountain Resources, Inc., a wholly owned subsidiary of Battle Mounrtain Gold Company (BMG, 1994). The northeastern block of the permitted area is owned by Earth Sciences, Inc. and leased to Battle Mountain Gold. The remainder of the permitted area is owned by Battle Mountain Gold Company (BMG, 1994). Site History and Previous Work The Battle Mountain Gold San Luis Project area was originally mined in 1887 by Ven Deist (URS, 1993). The then Rito Seco mine included a mill that utilized both cyanide leach and mercury amalgamation gold extraction processes. The Rito Seco mine was leased to ASARCO in 1931. A State of Colorado Bureau of Mines Inspector's Report dated August 15, 1946 states that the Rito Seco mine was then owned and operated by the Rito Seco Mining & Milling Company. Earth Sciences, Inc. operated the mine as a heap leach gold extraction operation in 1975. A cyanide spill from the Earth Sciences heap leach pad resuRed in a fish kill in the Rito Seco River downstream of the 1975 mine and initiated an official cease and desist of mining operations at the site (URS, 1993). Battle Mountain Gold Company commenced activities at the site in 1989. Ground water monitoring has been conducted since the commencement of current mining operations and is currently conducted on a quarterly basis. Ground water monitoring of ~ onsRe wells revealed the presence of cyanide, arsenic and mercury in Sante Fe ' Conglomerate ground water (CDMG, 1994). The most recent analyses of Sante Fe Conglomerate ground water collected from onsite monitoring wells did not indicate the presence of cyanide (Hayes, 1995~anganese concerrtrations were noted to differ in ~~ ~ `"' the three geologic units from which ground water has been collected. The highest ~~J s manganese concentrations have been detected in ground water from wells completed in the Pre-Cambrian Gneiss (monitoring welt D87-24)(Table 3; Attachment 1). Surface water quality monitoring has been conducted at the site since November 1987 (BMG, 1988). Surface water sampling from the Rito Seco River revealed a total cyanide w ~~ G detection of 90 parts per billion (ppb) at surface water station RS-5 on ,tune 29, 1994 (CDMG, 1994). Mercury was also detected at surface water stations RS-2 and RS-5 during July 1993 at concentrations of 0.4 ppb and 0.5 ppb, respectively. Mercury was '~5 5~ - not detected at upgradient surface water station RS-1 during the same sampling event. °' ~'~~~ Manganese has also been detected at elevated concentrations downstream of site operations relative to surface water analyses from an upstream location (RS-1). The arso~teaalawmmvR - 2 - m.w 4 Q+/+0.'~7 ..