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Privileged and Confidential—Attorney Client Communication v eoStec <br /> (i utsn!t;t"rs <br /> Desi on •''ion <br /> • Low population density <br /> Remote Location and • Challenging access to the Mine,especially during winter <br /> Site Constraints conditions <br /> • Constrained site footprint with limits to expanding pond sties <br /> *Mine historical flow data and guidance provided by OSMI for flow rate min/max assumptions <br /> **Source:CDPS Permit CO-0000003,Permit Modification 4 <br /> ***Temperatures taken from gauge in Ouray,CO,elevation 8,987';the Mine is located higher than <br /> temperature gauge at 10,600',so temperatures at the Mine are likely lower <br /> Water flow at the Mine varies seasonally with a minimum recorded value of 111 gpm <br /> and a maximum flow of 1,366 gpm as indicated in Figure 1. OSMI indicated the <br /> maximum flow value is likely an anomaly due to metering equipment and that a typical <br /> high flow is closer to 1,000 gpm. Spring runoff generally begins in May/June and <br /> continues through August/September, with low flow conditions in October through <br /> April. This broad range of seasonal flows is an important factor in the design and <br /> operation of high-elevation passive treatment systems. The hydraulic residence times <br /> will decrease during high flow, cold water runoff conditions,thereby reducing the <br /> amount of time that biological treatment can occur in a bioreactive system; additionally, <br /> there is increased risk of physical system flushing during high flow conditions and a <br /> potential degradation in biological performance due to lower water temperatures(Ness, <br /> Janin, & Stewart, 2014). <br /> too <br /> tdoo 111 121)0 <br /> 2 too() <br /> - Roo <br /> • <br /> • 00 <br /> 4i)) <br /> 2n) <br /> Q , •�O ^1 n� �\ •O O nl1 �O <br /> Y Y V <br /> 1/43 <br /> *Green horizontal line indicates Permit 30-Day Average <br /> Figure 1:Mine Discharge Water Flow Data <br /> Treatability Testing Report 3 December 11,2018 <br />