GENERAL35134 - Laserfiche WebLink

Home Browse Search

JD-ti. Modeling results for the JD-6 mine lack detail enough to support the interpretation that it should not be a DMO. The following explains shortcomings in the model interpretation. The report indicates that there is no data on depth to water. The absence of water depth data caimot be used to assume that there is no water within the limits of the dispersion plume as modeled. It is noted that the groundwater gradient, at SM-18, is approximately 180 feet/mile. If one assumes that such a groundwater gradient appears in the vicinity of the JD-6 mine, and if one further assumes that groundwater is present in quaternary alluviurn of the Paradox valley, and cormected to any bedrock aquifer, then the local water table would lie will within, in fact in the shallower portion, of the model dispersion plume. Without more compelling information on depth to water for the area, the Division should consider the JD-6 mine to be a DMO. [Emphasis added.] The Division also recites its reasoning related to the JD-8 Mine and states: JD-8. Modeling results for the JD-8 mine lack detail enough to consider it a non-DMO. The following explains shortcomings in the model that must be addressed before the model results, in consideration with other geological and hydrologic features, can be used to support anon-DMO status interpretation. The report states, essentially, that the faults in the region are non-transmissive, that they would divert water around rather than through faults. Support for this interpretation is absent. Without such support, it appears from the JD-8 cross-section that a contaminant dispersion plume from the 7D-8 waster rock pile would contact the Entrada and Kayenta formations. If the Entrada or Kayenta, which the report indicates are the regional aquifers, bear water, then contaminants should reach those zones in higher concentrations and in a shorter time than indicated by the author's interpretation of the model results. Unless the Division receives information sufficient to support the notion that the faults are non-transmissive, and unless it is shown that the Entrada and Kayenta in this area are not aquifers, the Division should consider the JD-8 mine to be a DMO. [Emphasis added.] In summary, then, the sole basis for treating the JD-6 mine differently than the SM-18 mine is that a monitoring well exists at the SM-18 mine which identifes that water is approximately 440 feet below the ground surface, and that, according to the Division, there is no evidence of the depth to groundwater at the JD-6 and the JD-8 mines because no such wells exist at those mines. 4