Laserfiche WebLink
13.0 Geochemical Data and Analysis <br />Denison has completed extensive geochemical evaluations of ore and development <br />rock during preparation of this EPP. The work plan is presented in the Development <br />Rock, Ore, and Soil Characterization Data Collection Work Plan to Address Designated <br />Mining Operations (DMO) Status Sunday Mines Group and Van 4 Mine (CDM 2008b), <br />which is included as Attachment J. The results of these investigations are presented in <br />the Environmental Geochemistry Evaluation of the Van 4 Mine, Montrose County, Colorado <br />(CDM 2009a), which is included in this report as Attachment A. This section provides <br />a summary of the results of the geochemical investigations. <br />13.1 Naturally Occurring Geological and Geochemical Conditions <br />The most important naturally occurring geochemical conditions in the vicinity of the <br />Van 4 Mine are natural enrichments of uranium-vanadium mineralization. The Van 4 <br />Mine is located within the larger Uravan Mineral District, and natural enrichments of <br />uranium, vanadium and other metals are present in the area. Although the Van 4 <br />deposit occurs in the sub-surface, outcropping uranium-vanadium mineralization is <br />present in numerous locations within the area (e.g. Cater 1954). This includes <br />numerous mining areas north of the Van 4 Mine within the Department of Energy <br />uranium reserve, as well as outcropping mineralized areas in the Bull Canyon <br />watershed. Other elements that are associated with naturally occurring uranium- <br />vanadium enrichment include arsenic, molybdenum, selenium, lead, and copper <br />(Rose et a1, 1979). <br />9 13.2 Mine Rock Geochemistry <br />13.2.1 Assessment of Potential Acid-Forming Rock <br />The section presents an assessment of the Van 4 Mine development rock regarding its <br />potential to be acid- forming. Evaluation of the potential for acid mine drainage is <br />based on evaluation of ABA data, observational data regarding mineralogy of the <br />mine rock, and effluent pH data from MWMP column tests. ABA data for <br />development rock and stockpiled ore show an overall low sulfur content and excess <br />of neutralization potential over acid potential in all samples. ABA data are compared <br />to the empirical thresholds to evaluate the potential for the rock to generate acid in <br />the future. The first threshold is based on the net neutralization potential (NNP). The <br />NNP of development rock samples collected at the Van 4 Mine range from 42.1 to 90.1 <br />tons per kiloton (t/kt) calcium carbonate equivalent (CaC03 eq). These NNP values <br />are greater than the 20 t/kt CaC03 eq. threshold, which indicates that the <br />development rock has a low potential to generate acid. ABA data are compared to the <br />second empirical threshold in Figures 13-1 and 13-2. This threshold is based on the <br />ratio between the neutralization potential and the acid potential (NP:AP). All samples <br />exceed the NP:AP ratio threshold of 4, which indicates that the samples are unlikely <br />to generate acid. <br />The ABA data support field observations that visible sulfide minerals are not present <br />and that ubiquitous calcite is present in the development rock and ore. Trace <br />concentrations of nitric acid soluble sulfur are present in several samples. These trace <br />13-1 <br />TA64986-0enison Mines\Task Order 4 - EPP Sunday Mines Group-Van4\Van4TlNAL Report\FINAL - Environmental Protection Plan Van4.doc