2009-06-08_REVISION - M1997032 (25)

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Hydrogeological Evaluation of Van 4 Mine Geologic and Hydrogeologic Conditions 2.1.3 Structural Geology The dominant geologic structure: Anticline, which is located in Pa. mine (Cater 1954). The Paradox salt intruded into the Paradox V' sedimentary rock units along a r dissolution of salt led to collapse: along the margin of Paradox Val Paradox Valley. in the vicinity of the Van 4 Mine is the Paradox adox Valley approximately 1 mile north of the Van 4 anticline was formed during the Permian period as lley area causing up-warping of the overlying clastic orthwest to southeast alignment. Subsequent of the salt intrusion and displacement of rock units ey. This major salt unit is still present beneath the A fault zone formed along the anticline's core. Faults within t Monogram Mesa and Paradox 2-1 and in cross-sectional view rgins of Paradox Valley during subsidence of the zone are present along the slope between lley. These faults are shown in map view on Figure Figure 2-2. The Van 4 Mine is situated on M{ nogram Mesa on the south side of Paradox Valley. The strata in the vicinity of the mine strike generally northwest and dip moderately towards the southwest. The loca? geologic structure is readily apparent when viewed from the southwest, as shown in the geologic cross-section. 2.2Regional Hydrogeologic Framework 2.2.10imate The Van 4 Mine is located within an and environment. Climatic conditions in this area generally include moderate to cold winter night time temperatures with hot summer daytime temperatures, l rge daily temperature fluctuations typical of and climates, and a large excess of ev poration over precipitation. Site-specific climatic data are n and precipitation data were co' Atmospheric Administration v record for this weather station are not available at the Uravan collected from a monitoring stz period of record for these data available for the Van 4 Mine. Therefore, temperature cted from the Uravan, Colorado, National Oceanic ether station (CLIMATEDATA 2008). The period of tends from 1961 through 2007. Pan evaporation data ation. Therefore, pan evaporation data were )n at Dead Horse Creek near Naturita, Colorado. The from 1971 to 1980. Table 2-1 shows the monthly avE period of record. Large daily ten and region, with upwards of 30° and day during most of the year greater and winter low temperat the winter are normally above fr Table 2-2 shows the monthly tots 2006 and Figure 2-3 is a box plot statistics. October, August, and S median monthly precipitation to -age maximum and minimum temperatures for the perature fluctuations are typical for this semi-arid to Fahrenheit (F) to 40° F fluctuations between night Summer high temperatures can reach 100° F or Tres can reach below 0° F, however, daytime highs in ezing (32° F). precipitation data for the period of 1961 through towing monthly total precipitation summary ptember are the wettest months of the year, with is of 1.36 in., 1.25 in., and 1.04 in., respectively. 2-4 • • • draft final van 4 hydn,geology raportdoc