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The aquifer underlying the coal is identified as the underburden aquifer. The wells in the
<br />underburden have been completed 17 to 64 feet below the coal, and samples are representative of
<br />water within the lower Dakota Sandstone. This confined aquifer is recharged along the
<br />Uncompahgre Plateau to the northeast and discharges towards the southwest. Transmissivity
<br />was measured at six sites and varies from 3.0 to 88 ft2 /day, averaging 38 ft2 /day. Hydraulic
<br />conductivity values varied from 0.07 to 4.5 ft /day, averaging 1.6 ft /day. This aquifer is not used
<br />locally to any great extent.
<br />The water in the underburden is characterized as hard, moderately alkaline saline water with high
<br />sulfate concentrations (average sulfate concentrations of 695 mg /1). Two wells show a
<br />calcium /magnesium sulfate type water while one well shows an alkaline sodium bicarbonate type
<br />water. The TDS varies from 960 -2648 mg /1, averaging 1619 mg /1. Dissolved iron levels vary
<br />from 0.02 to 2.51 mg /1 and average 0.63 mg /1. The sodium bicarbonate well occasionally
<br />exhibits pH levels that exceed the recommended agricultural standard. Another well shows
<br />manganese levels that exceed the agricultural standards. All wells meet the recommended water
<br />quality standards for livestock watering. The underburden aquifer does not produce acceptable
<br />water for domestic purposes; TDS, sulfate and ammonia standards are exceeded. Measurable
<br />trace element concentrations in the underburden aquifer include aluminum, arsenic, boron,
<br />cadmium, copper, fluoride, iron, lithium, manganese, mercury, nitrate, vanadium and zinc. The
<br />highest concentrations of arsenic, mercury and copper were measured in the underburden aquifer
<br />at the New Horizon 2 mining area.
<br />Ground water within 150 feet of the ground surface has been only minimally developed for use
<br />in the Nucla area. High salinities and occasionally high sodium or sulfate concentrations
<br />preclude its use as domestic, agricultural or stock water. In addition, moderate hydraulic
<br />conductivities are coupled with low sustained well yields (less than 1.5 gpm), discouraging
<br />sustained dependence on wells completed within these aquifers.
<br />E. Soils
<br />There were three major soils types in the original 220 -acre New Horizon Mine 2 area:
<br />Progresso -Bond Complex, 2 to 15 percent slopes; Barx — Barx, scalped — Barx, buried complex,
<br />1 to 4 percent slopes; and Lithic -Typic Haplaquolls, 1 to 3 percent slope. The Progresso -Bond
<br />complex is comprised of 40 percent Progresso, 40 percent Bond, 10 percent Barx (see below), 5
<br />percent Travesilla, and 5 percent Bowdish series soils. The Progresso series is classified as a
<br />fine-loamy, mixed, mesic, Ustollic Haplargid. The Bond series is a loamy, mixed, mesic Lithic
<br />Ustollic Haplargid. The main difference between these two is the distance to bedrock; Bond
<br />soils are shallow (17 to 19 inches to bedrock) while Progresso soils are fairly deep (36 inches to
<br />bedrock). Barx soil is found in the southeast corner, primarily within Mapping Unit D70B. It is
<br />classified as a fine- loamy, mixed, mesic Ustollic Haplargid. It is a deep, well- drained sandy
<br />loam formed in sandstone derived alluvium.
<br />The ephemeral drainages of the original Mine 2 area contained three families of Haplaquoll soils:
<br />Lithic, Lithic /Typic, and Typic Haplaquolls. The loamy, mixed, mesic, Lithic Haplaquolls are
<br />found in the upper reaches of the swales in the area and are the shallowest of the three series
<br />(bedrock at 11 inches). Lithic /Typic Haplaquolls (coarse- loamy, mixed, mesic, moderately deep
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