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Lake Emma was a glacial tarn in Sunnyside Basin at an elevation of approximately 12,250 feet <br /> msl. On June 4, 1978 Lake Emma drained into workings on the Spur vein causing extensive <br /> damage throughout the mine (Bird, 1986, p. 135). In areas of high permeability a lake can <br /> usually be considered to represent the water table. However, this does not appear to have been <br /> the case for Lake Emma. Two samples of the lacustrine clays which formerly were under Lake <br /> Emma were tested in August 1988 and shown to have permeabilities ranging from 1.6 x 10-' to <br /> 6.7 x 10-'cm/sec under 95% relative compaction (see Appendix B). These permeability values <br /> are very low and little water would have been transmitted through such material. Lake Emma <br /> is considered to have been perched on low permeability lacustrine clays and/or poorly fractured <br /> Henson Formation. <br /> Prior to the existence of the mine the gradient was approximately 0.1 feet/foot from the head <br /> of Sunnyside Basin to either Cement Creek, at Gladstone, or to the Animas River at the site of <br /> Eureka (see Table 1). If the pre-mine hydraulic head under Sunnyside Basin had been higher <br /> or lower the hydraulic gradient would have a different value, but the rate of change in gradient <br /> would be about the same to the southeast (toward Midway Mill site) as to the southwest (toward <br /> Gladstone). <br /> If permeability had been homogeneous and isotropic the ground water might have moved in <br /> either direction. However, as discussed in section 3.1.2 a strong anisotropy exists with <br /> enhanced permeability both in al northeast/southwest direction and also dipping southwest. In <br /> sanjuan\sunny\110361\oct9l.Rpt 19 <br /> w simon <br />