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investigation would not appear to be warranted. The selenium <br />levels of .1 and .12 ppm are at the "suspect" level established in <br />current Wyoming DEQ guidelines. The relationship between soil <br />selenium levels and plant tissue concentrations is not well <br />established, and the propensity of different plant species to <br />concentrate selenium is highly variable. The general consensus of <br />most researchers seems to be that the .10 ppm suspect level for <br />selenium is conservative, and that forage growing on such soils <br />would not pose a threat to grazing livestock unless primary or <br />secondary selenium accumulator species are a significant component <br />of the stand. Fourwing saltbush has been identified as a secondary <br />accumulator species, but it is a very minor component of the <br />current vegetation stand. No other primary or secondary <br />accumulator species appear to be present on the refuse area, nor <br />are they included in the seedmix. <br />The potential for plant selenium accumulation which might present <br />a threat to grazing animals would appear to be remote, but given <br />the "suspect level" of selenium in the refuse, tissue analysis of <br />representative samples of dominant plant species on 1 foot and 4 <br />foot depth plots would probably be prudent. <br />collection and_anaLv~sho»>d be_deselooed. with the re~~.]~s~Go~be <br />Summary <br />The early successional status of the vegetation stand on the refuse <br />pile, combined with topographic factors which could possibly mask <br />any effects of cover soil thickness on vegetative growth, precludes <br />definitive conclusions regarding potential for revegetation success <br />based on current vegetation conditions. As a result, decisions <br />regarding required cover depth will need to rely to a large extent <br />on soil characterization and information available from other <br />sources (applicable literature, comparable studies at other mines, <br />etc.). For these reasons, it is very important that the <br />clarifications regarding the soils portion of the study be <br />addressed. If, in the final report, the operator proposes to <br />replace a soil cover of less than four feet, the replacement depth <br />proposed will need to be justified based on the soils data and <br />applicable research. <br />c:\018refus.dtm <br />