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contaminated, and their value for determining SAR found questionable. Acid-Base Potential <br />analysis did not indicate a potential pn~blem with acid-forming material. Overall, the interpretation <br />of the overburden analysis showed that only nickel and selenium were found at levels that were of <br />any concern and that the mixing of the overburden during haulage would dilute the few samples <br />that were in the suspect range. A discussion of the analysis and interpretation can be found on page <br />779-16a of the permit application. <br />Groundwater <br />There aze predominately three aquifers of interest in the Marr permit azea: the Sudduth coal <br />aquifer, upland terrace deposits, and alluvial deposits. The coal aquifer has moderately poor yields, <br />except where it is faulted. The water is slightly alkaline and total dissolved solids concentrations <br />average 500 mg/1. The water is acceptable for stock and limited domestic use. <br />See the April 15, 1993, addendum to the December 9, 1992, Findings of Compliance for Permit <br />Renewal for discussion of upland terrace deposits. <br />Alluvium is found sporadically along all draws draining the mine site, next to the Canadian River, <br />and adjacent to the -linois River neaz the loadout. Monitoring has been performed along the draw <br />and adjacent to the tipple on the Illinois River. The discontinuous alluvium within the draws <br />draining the Marr permit area is predominately composed of clay with isolated sand and gravel <br />lenses. However, the permeability of the alluvium adjacent to the Illinois River is much higher and <br />is estimated to be 2500 gallons per day per squaze foot (gpd/ft2). <br />Surface Water <br />The surface hydrology of the general area, including the mine plan azea, consists of the high <br />altitude, semi-arid environment found in the upland pazks of the Central Colorado Rocky <br />Mountains. The average annual rainfall for the area is 11 inches. The major soil moisture rechazge <br />and runoff periods occur during the snowfall and subsequent thawing times of the winter and <br />spring. Climatologic records indicate increased precipitation during the summer months; however, <br />due to increased evapotranspirational effects during this warmer period, there is less impact to soil <br />moisture levels. <br />The mine plan azea is drained by ephemeral and intermittent stream systems. Starting at the north <br />end of the permit area and proceeding southward, one finds the Sudduth, Williams, Bush and <br />Bolton Draws. The Marr Strip drainage systems roughly parallel each other and flow to the <br />northeast where they join with the Canadian River, approximately one mile east of the permit azea. <br />In the tipple azea, the -linois River has a base flow rate of about six cubic feet per second (cfs) and <br />a recorded 100-year flood discharge of 2970 cfs. The Illinois River has its source in the Never <br />Summer Range to the southeast. The -linois River, after passing the tipple area, flows in a <br />northwest direction and bypasses the [own of Walden on the southwest. Approximately one-mile <br />northwest of Walden, the Michigan River merges with the Illinois River. The Illinois River in turn <br />flows north to merge with the North Platte River. <br />Marr Mine Permit Renewal 04 <br />11 January, 2002 <br />-6- <br />