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treatment facility, the Rito Seco is deeply incised into unconsolidated alluvial <br />material that is comprised of weathered remnants of the underlying Santa Fe <br />Formation and Precambrian bedrock. As such, the naturally occurring hydrologic <br />and geochemical processes influencing the baseline water quality of the Rito <br />Seco, for purposes of establishing system-based effluent standards, are more <br />appropriately evaluated using historical water quality data obtained from the <br />downgradient water quality monitoring stations RS-2 or RS-5, the latter of which <br />integrates the combined hydrologic and geochemical processes of the Rito Seco <br />upgradient of that location. <br />The EPA asserts that the inactive "Earth Science Pit" may contribute metals <br />loading to the Rito Seco in the vicinity of sample location RS-3 without providing <br />supporting evidence. BMRI is unawaze of any water quality data that would <br />suggest that the historical activities conducted by Earth Sciences, Inc. (ESI) have <br />resulted in continuing effects on the water quality of the Rito Seco. There is no <br />"Earth Sciences Pit." The only pit associated with mining conducted by ESI was <br />completely subsumed during the mining and backfilling of the East Pit. As part <br />of the TR-015 Response Plan, BMRI installed a backfill groundwater monitoring <br />well (BF-8) in the backfilled East Pit that has never recorded a measurable <br />amount of groundwater in the well bore. Thus, the "Earth Science Pit" could not <br />be a source of metal loading to the Rito Seco because there is no groundwater in <br />the East Pit. <br />ESI operated a heap leach system in an azea on the south side of the Rito Seco <br />(opposite from the mining activities conducted by BMRI). The heap leach <br />materials were removed by BMRI and beneficiated through the mill circuit with <br />resultant tailings deposited in the lined, zero-dischazge tailings basin. After <br />removing the heap leach material, the liner was removed and heap leach area was <br />reclaimed by the addition of topsoil and vegetation. <br />Historical water quality data have been collected at the surface water station RS-3 <br />that is located upgradient of the historic ESI heap leach area. The water quality <br />Mountain Resources, lnc. HJ7 Gro 1 inns <br />2 July 1l, 1000 <br />