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Ms. GrU 1. I.cnkry <br />11/I r/99 <br />Page 3 <br />This resulted in some of the highest flows ever recorded at point OOIA. CC&V has previously <br />submitted flow data for the NUD, SUD, SP, and point 001A in the form of charts and tables. The <br />correlation between high flows and precipitation has been made clear in previous submittals. The <br />high flows have tended to flush out the CN„~ in the residual Carlton Mi]] tailing material that <br />could not be removed from the Arequa Gulch area prior to construction of the VLF and/or the <br />Ironclad Mill tailing material that was used as the base material underneath a portion of the VLF. <br />This upset relationship between precipitation, flow, and CNw„o is further demonstrated by the <br />most recrnt cyanide data. The 30-day average CNw~o concentration reported in the September <br />1499 Discharge Monitoring Report ("DMR")decreased for point OOIA to below the 0.021 mg/1 <br />permit limit. Similarly, the 30-day average CNw~o value reported for October was 0.013 mg/1. <br />The lower CNweo concentrations in September and October are directly related to the reduction <br />in precipitation and the resultant decrease of flows at point OOlA recorded during these months. <br />Preoipitation totaled 0.91 inches for September and 1.39 inches for Oetober. Monthly average <br />flows at point OOIA decreased from 87.3 gpm in August to 21.9 gpm in October. <br />Finally, due to the exposure of the water to sunlight, CN,,,,I is partieliy converted to CNwao. <br />CC&V has demonstrated that this conversion is possible and is a recognized phenomenon in the <br />literature. As such, an upset did indeed occur at point OOIA during the months of May, June, July, <br />and August 1999. <br />Pleaze contact me at 719-689-0041 if you have any questions, comments, or need any additional <br />information to support the upset condition at OOlA. <br />Sincerely, <br />W v~ <br />Scott A. Ixwis <br />~~~ <br />Manager, Environmental Affaus <br />Attachemrnts (1) <br />cc: Melanie Pallman - U.S. EPA, Region 8 (SENF-T), w/enclosures- Z 217 656 399 <br />Dave Akers - WQCD <br />Z00-qol' ElJPO d lZE-1 YSZEBB98lll 7M1 0107 ~I~J:ae~d 9Y~El 88-l0-730 <br />