2019-10-10_HYDROLOGY - M1980244 (18)

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We ITASCK Denver, Inc. In general, iron and aluminum had the highest measured concentrations,with average values of 27,700 and 13,000 milligrams per kilogram (mg/kg) for all the samples, respectively. The iron content is likely related to the oxyhydroxide and silicate minerals identified in the mineralogic analysis, as well as smaller contributions from siderite, pyrite, and jarosite. Aluminum is also associated with silicate minerals as well as alunite in some samples (i.e., 138 and 1312). Potassium concentrations were the next highest,with an average of 6,300 mg/kg. Potassium is also primarily associated with silicate minerals, such as K-feldspar. In general, the solid-phase composition is not strongly associated with the sample rock-type group and is dominated by elements that are common in the relatively non-reactive but abundant silicate minerals. 3.5 METEORIC WATER MOBILITY PROCEDURE The static leach properties of each of the 12 Phase II samples were investigated using MWMP testing. The MWMP is designed to provide an indication of readily soluble constituents in mine rock that may be susceptible to leaching by meteoric water, i.e., precipitation. 3.5.1 Methods The MWMP procedure is detailed in NDEP(1996).The procedure consists of a single-pass column leach over a 24-hour period using a rock sample to extraction fluid (effluent) ratio of 1:1. The extraction fluid used was Type II reagent-grade water,which most closely simulates precipitation west of the Mississippi River (NDEP 1996). Leachate was collected, preserved, and analyzed by ICP-MS and ICP-AES. An unpreserved aliquot of leachate was analyzed for pH and temperature at the time of collection. 3.5.2 Results The MWMP leachate composition for each sample is listed in Table 3-5, and the original laboratory reports are provided in Appendix B. It is important to note that the concentrations measured in MWMP test leachate do not necessarily reflect concentrations expected under the 22