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<br />-zo- <br />Auger hole tests were performed to determine the hydraulic conductivity, <br />(permeability) of the alluvial flood plain materials. The permeability <br />determined from the auger hole tests ranged from 0.014 ft/d to 2 ft/d. <br />Attempts to conduct an auger hole test at one hole failed because the <br />permeability was too high. A pump test was performed on that hole, and from <br />the observed drawdown, the permeability was estimated to be about 1,880 ft/d. <br />The alluvial flood plain ground water is a calcium-bicarbonate type water with <br />a chemistry similar to that of the Purgatoire River (see permit application <br />Exhibit 6, Figures 12 and 14), but with slightly higher concentrations of the <br />major ions. The only significant difference with respect to the major ions is <br />an elevated sodium concentration in the alluvium relative to that in the <br />stream. Although seepage from the New Elk Mine refuse pile has high sodium <br />concentrations, mining activities are not the sole cause of the elevated <br />sodium levels. Sodium is high in all four wells. The sodium is probably <br />being contributed, in part, by the dissolution of one or more sodium salts <br />contained in the soils or alluvium. <br />Concentrations of major ions and the conductivity of alluvial wells at the <br />downstream Golden Eagle Mine site are less than the concentrations and <br />conductivities of wells at the New Elk Mine site (Exhibit 6, Table 3). This <br />is probably the result of inflows of better quality water from the North Fork <br />of the Purgatoire that joins the Middle Fork of the Purgatoire between the two <br />mine sites. <br />D. Surface Water <br />The Purgatoire River, a tributary of the Arkansas River, is the major surface <br />drainage feature of the area. The headwaters of the Purgatoire are located on <br />the eastern slope of the Sangre de Cristo Range west of the study area. The <br />three major branches of the river, the North fork, Middle Fork, and South <br />Fork, all converge within the study area. The New Elk Mine is located on the <br />Middle fork, about 1.5 miles upstream of the confluence of the North and <br />Middle forks of the river. The Golden Eagle Mine is located downstream of the <br />confluence of the North and Middle forks of the Purgatoire River, and <br />approximately two miles upstream of the confluence of the South Fork and the <br />main stem of the Purgatoire River at Weston. <br />The United States Geological Survey (USGS) operates surface water gaging <br />stations at Madrid, Colorado on the main stem of the Purgatoire River and at <br />Stonewall, Colorado on the Middle Fork. The Madrid station is Located at the <br />downstream limit of the study area and gages the runoff from approximately 550 <br />square miles of watershed, while the Stonewall station is approximately four <br />miles upstream of the New Elk Mine and gages runoff from a 52.1 square mile <br />drainage area. Between these two stations, numerous ephemeral and <br />intermittent Streams, in addition to the North and South forks mentioned <br />above, join the river. Records of runoff as measured at Madrid are available <br />from 1972 to the present and at Stonewall from May, 1978 to September 1981. <br />The headwaters of the Purgatoire River system are in excess of 9,000 ft. <br />elevation and receive substantial snowfall. For example, the mean annual <br />precipitation at North Lake at the head of the North Fork (elevation 8,800 <br />ft.) is 20.55 in. of which 1.48 in. is in the form of snow. On the other <br />hand, the mean annual precipitation at Trinidad (elevation 6,030 ft.) is 13.22 <br />