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<br /> Pti , igl:Paramaters+Rko Seco t3[var. <br />,.. <br /> <br /> <br />Samplg No: :: ::::.:::::.: <br /> <br /> <br />:::>: <br />,: o <br /> <br />:::;:.::Tun <br />pxehea: (; C} :, :. <br /> <br />pH::{5teniiard:Lnlls}:' ; <br /> <br />:: <br /> <br />;;:; ConducU... ;?: -'': ;: <br /> ivsl+xn} <br />BMSW-01 5.2 7.37 110 <br />BMSW-02 7.7 8.17 160 <br />BMSW-03 9.8 8.26 160 <br />BMSW-05 18.6 6.69 180 <br />An intermittent tributary of the Rito Seco enters the river from the south at a point adjacent <br />to the former location of the Earth Sciences heap leach pad and within the permit <br />boundary. The point at which the tributary enters the permit boundary is designated as <br />surface water station RS-3 (Fgure 2). The flow rate of this tributary at the permit <br />boundary was measured to reach a maximum in 1988 of 0.5 cfs (BMG, 1988). <br />The mill/tailings facility is situated in a drainage that contributes flow to Culebra Creek <br />approximately 6 miles downstream. Overland flow originating from the area of the mill <br />facility is diverted into the tailings pond. Overland flow upstream of the mill facility is <br />diverted into the pre-existing channel at a downgradient location, thus minimizing the <br />potential for entry of flood waters to the facility. The diversion ditches carrying upgradient <br />flow around the facility were designed to cant' the peak discharge from th®100-year, 24 <br />hour precipitation event (BMG, 1989). Measurable flows in this drainage are infrequent <br />(BMG, 1994). <br />3.0 SOURCE CHARACTERISTICS <br />The known hazardous substances that are associated with past and current mining <br />activity at the site include metals and cyanide. Mercury in particular was reportedly used <br />at the site during initial gold extraction operations at the tum of the century. Mercury is <br />also a trace contaminant in the wastewater generated from current milling activities; a <br />sample collected from the onsite leachate collection pond on September 13, 1991 <br />contained 1.3 ppb total mercury. Cyanide was used historically and in the present active <br />gold extraction operation at the site (URS, 1993; CDMG, 1994). Tailings produced from <br />the gold extraction process consist of finely ground rock of which 80 percent is minus No. <br />srso~seaa~~mwvmric <br />-4- <br />(rta 4 m/toiay <br /> <br />