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<br />The current site operator is Battle Mountain Resources, Inc., a wholly owned subsidiary <br />of Battle Mountain Gold Company (BMG, 1994). The norfheastem block of the permitted <br />area is owned by Earth Sdences, Inc. and leased to Battle Mountain Gold. The <br />remainder of the permitted area is owned by Battle Mountain Gold Company (BMG, <br />1994). <br />Site History and Previous Work <br />The Battle Mountain Gold San Luis Project area was originally mined in 1897 by Ven Deist <br />(URS, 1993). The then Rito Seco mine induded a mill that utilized both cyanide leach and <br />mercury amalgamation gold extraction processes. The Rito Seco mine was leased to <br />ASARCO in 1931. A State of Colorado Bureau of Mines Inspector's Report dated August <br />15, 1946 states that the Rito Seco mine was then owned and operated by the Rito Seco <br />Mining & Milling Company. Earth Sciences, Inc. operated the mine as a heap leach gold <br />extraction operation in 1975. A cyanide spill from the Earth Sdences heap leach pad <br />resulted in a fish kill in the Rito Seco River downstream of the 1975 mine and initiated an <br />offidal cease and desist of mining operations at the site (URS, 1993). Battle Mountain <br />Gold Company commenced activities at the site in 1989. <br />Ground water monitoring has been conducted since the commencement of current mining <br />operations and is currently conducted on a quarterly basis. Ground water monitoring of ~ <br />onsite wells revealed the presence of cyanide, arsenic and merctry in Sarne Fe ' <br />Conglomerate ground water (CDMG, 1994). The most recent analyses of Sante Fe <br />Conglomerate ground water collected from onsRe monitoring wells did not indicate the <br />presence of cyanide-(Hayes, anganese concermations were noted to differ in ^rd ~ ` <br />the three geologic un om which ground water has been collected. The highest ~".~ S <br />manganese concentrations have been detected in ground water from wells completed in <br />the Pre-Cambrian Gneiss (monitoring well D87-24)(Table 3; Attachmern 1). <br />Surface water quality monitoring has been conducted at the site since November 1987~~'~°~p <br />(BMG, 1988). Surface water sampling from the RRo Seco River revealed ~ snide ~ - <br />~ ~,, n, <br />detection of 90 parts per billion (ppb) at surface water station RS-5 on June , 1994 <br />(CDMG, 1994). Mercury was also detected at surface water stations RS-2 and RS-5 <br />during Juty 1993 at concentrations of 0.4 ppb and 0.5 ppb, respectively. Mercury was 'a9 sl <br />not detected at upgradient surface water station RS-1 during the same sampling evern. °' ~ ~ <br />Manganese has also been detected at elevated concentrations dovmstream of site <br />operations relative to surface water anayses from an upstream location (RS-1). The <br />axo~~sou~.mrcoArx - 2 - m.• a arnwaa~ <br />