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Average Annual Water Depletion Estimate <br />• Tab 16, Attachment 16-1, Water Rights Investigation and Plan for Augmentation for the Yoast Mine, <br />provides a detailed account of existing water usage at the Yoast Mine. Following is an estimate of <br />future water depletions based on the life-of-mine plan. <br />u <br /> <br />Evaporation from sediment ponds and haul road watering will be the primary causes of surface water <br />depletion in the Yoast area. The Yoast Mine area has two (21 existing ponds and is proposing to <br />construct three 131 additional ponds over the life of Yoast operation. The annual net lake evaporation <br />for Hayden, Colorado is 26.46 inches. <br />Total maximum evaporation from the existing ponds have been calculated at 6.5 acre-feet annually, <br />while the proposed ponds would result in the lass of an additional 6.2 acre-feet annually. This <br />estimate assumes that all ponds are full to the level of the principal spillway at all times li.e. worst <br />case scenario). <br />Based on records maintained by the State Engineers Office and SCC, the annual usage of water to <br />suppress dust on the haul roads has averaged 40 acre-feet per year with one additional acre-foot <br />consumed as domestic water. This results in a total annual usage of 53.7 acre-feet of surface water <br />per year and is approximately 54 percent of the Windy Gap trigger level of 100 acre-feet annually. <br />AVERAGE ANNUAL WATER DEPLETION ESTIMATE <br />YOAST MINE <br />Facilit Acres Acre-Feet <br />Pond 010 lexistin 1 2.5 5.5 <br />Pond 011 (existing) 0.5 1 .0 <br />Pond 012 1 ro osed) 1.4 3.1 <br />Pond 013 1 ro osed) 0.6 1 .3 <br />Pond 014 (pro osed) 0.8 1.8 <br />Domestic Use --- 1.0 <br />Haul Road Waterin --- 40.0 <br />Total 53.7 <br />Note: Surface acres of the ponds assume that water level is at principal spillway <br />elevation. <br />Water usage (domestic and haul road watering) derived from Table 1, <br />Attachment 16-1. <br />The table above represents the only sources of water depletion at the Yoast Mine. There are no water <br />depletions due to pit water evaporation, conveyor sprays, coal processing, bath house consumption or <br />domestic water use. <br />Revised 9/99 <br />