HYDRO22615 - Laserfiche WebLink

Home Browse Search

Me. Carta 1. Itnkey I (/16/99 Page 2 The flows from the NUD, SUD. and SP merge at the concrete sump and continue down Arequa Gulch (for approximately 400') to the sediment pond. It should he noted that a minor amount of water flows into the concrete sump from three springs neaz the NUD, SUD, and SP. The combined flows from these springs are only 1D gallons per minute ("gpm") during peak flows. Normally the spring flows aze less than about one gpm Cl`lwno concentrations in the springs are typically near or nt the 0.01 mg/1 detection limit. From the sedimrnt pond, water continues down Arequa Gulch (for approximately 400') to the flume installed at point 001A. Although the flows from NUD, SUD, and SP have relatively low CNw~o values, the flows do contain measurable amounts of CN,o„I. As shown in ?able 1, between May 1, ] 999 and August 31, 1999: • Flows from the SP had no CNwno detections (out of 34 samples) but had measurable levels of CN,,,,I in 33 of 33 samples; • Flows from the NUD had 34 CNw~o detections (out of 34 samples) and had measurable levels of CNstil in 33 of 33 samples; and • Flows from the SUD had two CNw~o detections (out of 34 samples) and had measurable levels of CN„dl in 34 of the 34 samples. What appears to be happening as the water flows from the convete sump to the flume is that a portion of the CN~nI is being converted to CNwnn• Although the estimated one day lag tune for the combined flows from the NUD, SUD, and 5P to reach point OOIA complicates the analysis, the conversion of CN,nnl to CNw~o appears to be driven by the exposure of the flows to sunlight. CN„ei comprises al] forms of cyanide including the iron cyanides (i.e. hexacyanofetrates). CNw,,n comprises the metal-cyanides (e.g., Zn, Cu, Ag, Hg) plus the free cyanides (i.e., CN-, HCN). The iron cyanides are stable under certain conditions and can form insoluble precipitates. Howevtt, the iron cyanides are unstable in the presence of ultraviolet light (Smith and Mudder, 1991). Ultraviolet light will breakdown the structure of the complex and release the free cyanide radical CN- and HCN. This in tum is able to stay dissolved or complex with aqueous metals forming CNw~. CC&V conducted en experiment to test the hypothesis of the conversion of CNp„I to l';Nw,~. Tn the experiment, individual samples of the NUD, SUD, and SP were collected and combined according to their respective flow rates. One part of the sample (150 mg/1) was immediately preserved, and a second porton of the sample was placed in a l liter bottle and tightly sealed and allowed to sit in the daylight for a day and then preserved. Results of the experiment showed that the immediately preserved sample had a CNmul concentration of 0.04 mg/l and a CNwAo concentration of less than the detection limit of 0.01 mg/1. The sample in light had a CN,,,,I concentration of 0.043 mg/1 end CNq„o value of 0.03 mg/I. The results of this experiment suggest that light ie a degradation mechanism and is consistrnt with findings reported in applicable literature (Smith and Mudder, 1991; Chetwin, 1989; Huiatt et. al., 1982). Tn summary, CC&V has demonstrated that the Victor area received excess precipitation between May 1, 1999 and August 31, 1999 in several proviouc letters. The 42-inch snowfall that fell in the area at the end of April is believed to have slatted the upset condition. CC&V has previously provided the precipitation dnta and snowfall data to demoeatratc the access precipitation. The excessive precipitation resulted in flows much higher than normal in the NUD, SUD, and SP. Z00-q61' EO'd lZE-1 V52EB9981li Ot8'1 0107 A107~W01d 94~E1 AB-l0-030