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February 1998 Hayden Culcb Mint ' Pbase 2 & 3 Bond Release Application ~ Pape 75 <br />increasing trends may have peaked and chat recent concentrations are approaching constituent <br />values observed eazly in the reclamation liability period. <br />Seep/spring discharge data is not very conclusive. Most reported flow rates are based on visual <br />estimates of flow. Site investigations suggest chat flow from RSP-1, RSP-5, and RSP-6 has been <br />minimal, while flow from RSP-2 and RSP-3 has remained relatively constant since 1987. <br />However, data indicates that discharge from RSP-4 has increased since 1987. It is assumed that <br />some of the recent increase could be attributed to the above average precipitation which <br />occurred during 1996 and 1997. The increased spring discharge to Hayden Gulch is consistent <br />with predictions made in the PHC. <br />Surface Water <br />Two surface water monitoring sites are located on Hayden Gulch and have been monitored <br />since 1987. Upper Hayden Gulch (UHG) is located above the mine dis[urbance area, and <br />Lower Hayden Gulch (LHG) is located downstream of the mine disturbance area at the permit <br />boundary. In anticipation of Phase II/III bond release, HGCC initiated an expanded surface <br />water monitoring program. Three new locations were added to the monitoring network; an <br />additional Hayden Gulch site immediately upstream of the confluence with the Williams Fork <br />River (monitoring site HG-1S), and two sites on the Williams Fork River, upstream (WF-2) and <br />downstream (WF-1) of the confluence with Hayden Gulch. <br />In general, constituent concentrations measured in surface waters since 1987 were less than <br />corresponding baseline concentrations. Sodium, sulfate and TDS concentrations measured in <br />discharge from Pond HGS and at LHG frequently exceeded the corresponding maximum <br />• baseline values. However, downstream of the permit boundary at HG-1S, constituent <br />concentrations were generally less than the baseline value. In addition, samples collected from <br />the Williams Fork River indicate that constituent concentrations were well below <br />concentrations measured in Hayden Gulch samples. <br />U <br />Surface water constituent concentrations downstream of the permit boundary were generally <br />less than applicable surface water numeric standards with the exception of sulfate. Sulfate <br />concentrations in samples collected at LHG routinely exceeded the Colorado numeric <br />standards, however, baseline surface water concentrations also frequently exceeded the sulfate <br />numeric standard. <br />Beneficial uses of Hayden Gulch surface waters are limited to livestock and wildlife watering. <br />HGCC is not aware of any current or historical irrigation use of water from Hayden Gulch. <br />Results of Hayden Gulch surface water samples were compared to WDEQ livestock use <br />guidelines. Constituent concentrations in Hayden Gulch surface waters did not exceed the <br />WDEQ livestock guidelines. <br />Trend analyses indicate that surface water constituent concentrations have remained relatively <br />constant during the reclamation liability period. <br />Montgomery Watson Americat (dba TerraMatrizf ' P.O. Boz 774018 <br />Steamboat Springs, Colorado 80477' (970J 879-6160 <br />V.11)11P1.e)bJ°. ,Rde.Y AgJUw\Tm1Mu1LJBwd RdrrAgJr~om <br />