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Privileged and Confidential-Attorney Client Communication Geosyntee con"Idtant" Table 1: Mine Site Design Considerations • Seasonal changes in pumped water volumes from the portal — low flow is typically October through April Water Flow Rate* • Design low flow: 100 gallons per minute(gpm)(historical low on record was 1 11 gpm in December 2015) • Design high flow: 1,215 gpm** o Permit 30-Day Average: 1.75 MGD(1,215 gpm) • High monthly average temperature:July, 78°F Climate and • Low monthly average temperature: January, 15°F Temperature Highest recorded temperature: June,960F Fluctuations*** • Lowest recorded temperature:January,-22°F • Average number of days below 32°F: 182 Water Temperature • To be evaluated through pilot-scale testing as discussed in Section 3 of this Work Plan Precipitation** • 40"/year Evaporation** • 35"/year Elevation • Mine elevation is 10,600' • Low population density Remote Location and • Challenging access to the Mine, especially during snow Site Constraints conditions • Constrained site footprint with limits to expanding pond sizes as described in Section 2 of this Work Plan *Mine historical flow data and guidance provided by OSMI for now rate min/max assumptions **Source:CDPS Permit CO-0000003,Permit Modification 3 ***Temperatures taken from gauge in Ouray,CO,elevation 8,987';the Mine is located higher than temperature gauge at 10,600',so temperatures at the Mine are likely lower Water flow at the Mine varies seasonally with a minimum recorded value of 111 gpm and a maximum flow of 1,366 gpm as indicated in Figure 1. Spring runoff generally begins in May/June and continues through August/September, with low flow conditions October through April. This broad range of seasonal flows is an important factor in the design and operation of passive treatment systems (Ness, Janin, & Stewart, 2014). Treatability Study work Plan 2 February 8,2018