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• Leach ate Characteristics and Overburden Attenuation <br />In the unlikely event that infiltrating water would produce a leachate, utility <br />wastes placed in the mine may release several elements in concentrations greater <br />than would otherwise occur. <br />Of the 22 chemical parameters selected for analysis in this study, 8 have been <br />selected for presentation in this section (refer to Table 4.3-12). These eight <br />chemical parameters have concentrations which exceeded the limits of the EPA's <br />Primary and Proposed Secondary Drinking Water Standards as set forth in Table <br />4.3-13. These limits will be referred [o as the water quality criteria. The <br />parameters are barium, aluminum, boron, chromium, molybdenum, sulfate, vanadium, <br />and manganese. <br /> All of the chemical species that may leach from the ash or ash-gypsum mixture, <br /> with the exception of sulfate, can be reduced in concentration to drinking water <br /> quality by attenuation in the overburden. <br />Methods Used <br />The characteristics of the wastes under flow conditions, in general, and of the <br />pollutant mobility through the waste body in particular, were evaluated using <br />column leaching studies. Well designed column leaching tests are believed to <br />represent (nn a Lahnra[ory scale) the principal mechanism for any potential po1- <br />lu[ant migration for the disposal systems under consideration at the Trapper <br />Mine. I[ is anticipated [hat the results of column leaching studies should pro- <br />vide data on pollutant release from the was [e and their attenuation and removal <br />in Che overburden and, consequently, provide enough information to assess envi- <br />ronmental impacts of various waste disposal options at [he Trapper Mine if perco- <br />lation should occur. <br />The medium used in the column studies should be selected from [he class of likely <br />waste material and disposal site substrata. Ln addition, [he column arrangement <br />'~ should represent as broad a range of waste disposal placement options as prac[i- <br />cal. In order [o evaluate [he chemical interactions between ash, and ash and <br />4-55 <br />