2012-02-28_REVISION - M1980244 (65)

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Cripple Creek & Victor Gold Mining Company Squaw Gulch Valley Leach Facility Design 7.0 Water Balance 7.1 Water Balance Model A dynamic, probabilistic water balance model was developed and used to support the design of the VLF. The water balance model is the same as that used for the Cresson Project VLF and considers operating volume, draindown volume, solution accumulation due to seasonal climatic variation at a 95- percent confidence level, the 100 year /24 -hour design storm event, and available pore space of the ore within the PSSA. The model incorporates probability to simulate variability in the site climate, consistent with previous Amendments. The model also simulates variability in both precipitation and evaporation for inflows and outflows for the VLF. The VLF water balance utilizes the same draindown and uptake functions as those used in the Cresson Project VLF. These functions were calibrated against actual measurements of solution flow and PSSA levels from the existing VLF. The VLF water balance model has the following components: • Climatic data inputs for precipitation and evaporation; • Ore loading, facility volumes, areas of coverage, and phases; • Material properties for initial moisture contents, field capacity, leaching moisture, and moisture uptake; • Process solution flows from the PSSA to the process plant; and • Solution application rates. The water balance model was developed using the GoldSim modeling software. GoldSim is a graphic- oriented, computer program that is designed to conduct dynamic, probabilistic simulations to support decision - making and design. The software is available through the GoldSim Technology Group LLC and was initially developed to model the complex environmental data for the U.S. Department of Energy (DOE) Yucca Mountain High Level Waste Repository Project. The software has been reviewed and accepted by the U.S. Environmental Protection Agency (U.S. EPA). The water balance was developed as a monthly model covering the operational period from July 1, 2016 through June 30, 2025, for ore stacking and leaching. After ore stacking and leaching, the model simulates the post- mining leaching period of the VLF, whereby the ore continues to be leached without additional ore being added. The post- mining leaching operations period for the VLF is approximately 8 years and ends in about 2033. The post- operations period, during which the ore is rinsed and water evaporated, occurs from the end of post- mining leaching. Project No.: 74201125G0 Page 36 1 September 2011 amec°