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2004 Annual Hydrologic Report Page 2 <br />• Surface Water <br />Water flow and quality on the Colorado River is monitored by the U.S. Geologic Survey (USGS) <br />at various locations. The closest location is Station No. 09095500 which is located upstream <br />approximately 7 miles north east of the mine site. Water quality and flow from this site are used <br />as a general representation of the Colorado River up gradient of the mining operation. There is <br />a diversion to the Government Highline Canal, the addition of Plateau Creek and the addition of <br />other minor drainages between the monitoring site and the mine site. Data Pages SQ-37 <br />through 42 includes information supplied by USGS on this site in 2004. The total flow at this site <br />for the Year was 1,645,000 acre-feet which is 59% of the normal average flow for the period <br />1934 -2004 (2,771,000). The estimated TDS load for the Year was 1.05 million tons. This <br />estimate is made using the values for dissolved solids reported on page SQ-41 times the <br />monthly flow in acre feet. The low flow for the Year was recorded as 1,040 CFS on January 6, <br />2004. The river was carrying approximately 0.94 tons of TDS per acre-foot on January 6'". This <br />flow and TDS load equates to approximately 1,940 tons of Total Dissolved Solids, TDS, being <br />carried by the river past the mine that day. The mine discharge on January 7`h (the closest <br />monthly analysis), was 275 @ 1293.5 mg/I TDS; resulting in approximately 2.1 tons of TDS <br />being discharged. Comparing the calculated TDS load in the River at low flow and the mine <br />• discharge near the same date, the maximum increase in the River's TDS as a result of mine <br />discharge would have been 0.11 %. <br />This Year's mean daily flow values for the Cottonwood and Rapid Creek flumes are included on <br />data pages SG-37, SH-26, and SI-26. Flow at SWGS-001 is presented graphically on data <br />page SG-38. As usual, the flow in these Creeks is largely controlled by the City of Palisade, <br />depending upon their need for domestic water. Also, irrigation water is diverted from the creeks <br />by private water right holders at various locations. Table SO4-1 was prepared to show the <br />average monthly flows during the primary irrigation season when low flow in the creeks is <br />critical. Gaps in information are due to problems with the recorder or flows below the minimum <br />recording level of the recorder. Minimum recording levels of the flumes are listed at the bottom <br />of Table SO4-1. <br />Monitoring on Coal Creek and Jerry Creek was started in 1995. The crest stage gages installed <br />in Coal Canyon drainage and Jerry Creek in 1996 were destroyed by a storm in the summer of <br />1998. Discussions with DMG have indicated there is no need to monitor the upstream locations <br />SWGS 07 and 09. The creeks will only be monitored at the lower monitoring points. The <br />ephemeral flow in Coal Creek is measured at culverts located between the two refuse disposal <br />areas, SWGS O6. These culverts provide a stable cross section and are accessible throughout <br />the year. The intermittent flow in Jerry Creek is measured at the culvert near the Highline Canal, <br />• SWGS 08. Beginning July 1999, instantaneous flows are to be monitored monthly. Data taken <br />during the Year are listed on data pages SR-2 for Coal Canyon and SS-2 for Jerry Creek. <br />