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-_ q - ' ~dward•Clyde Consultants <br />G"~ 'Climax1Molybdenum Company <br />_ September- 22, -1981 <br />Page 6 <br />- CON:.LUSIONS ~ - - <br />To .assist you in evaluating the~dust suppressants, we developed a matrix <br />to compare the effect of each product on your tailing dams, as shown on <br />.Table V.. For the purpose of the matrix analyses we ranked the chemicals <br />from t.to'6 foz any given item_considered,..with a,ranking of 7 representing <br />the most favorable chemicals and the ranking of 6 representing the least <br />favorable chemicals... If,..in our opinion,-aspects of two or more of chem- <br />icals were similar for any of the items considered, we, ranked the chemicals <br />equally. Where no one chenu.cal was clearly the more favorable or least <br />favorable for a given item, rankings of 1 and 6, respectively, were not <br />assigned. The chemical r~ith the lowest total points should, then, be the <br />_ -~ more favorable. We did not attempt to rank the chemicals with respect to <br />field equipment and manpower required as all of the manufacturers recom- <br />mended using a power spray unit and one man per unit. Also, we did not <br />atttempt to evaluate the acceptance of the products from the mill pro- <br />cessing standpoint, as we understand you will do that. <br />Based on the matrix analyses, it appears the NALCO 1DA655 and 6820 would <br />Y ~ be "preferred" chemicals mainly because of the lower cost per square yard, <br />complete freeze-thaw stability and lower storage temperatures. The <br />_ ARCO.2010 chemical appears to be the least favorable due to the highest <br />' cost per square yard and no freeze-thaw stability. The chemicals <br />ARCO 2000, Sodium Lignin Sulfonate and Coherex received intermediate <br />rankings. <br />We emphasize that the test program described above was conducted under <br />laboratory controlled conditions and that actual field conditions, layer <br />frequency, physical features of the dust suppressant layers, and other <br />factors would need to be considered to enable realistic evaluation of the <br />effects of the dust suppressant layers on your tailing dams. we recommend <br />a field study be conducted to assist in judging the effects of the dust <br />suppressant treated layers o~~*- tailing dams. <br />C. G <br />Zf•you have questions, <br />C\~cerTia=t"t'"`om <br />Chief, Soils Division <br />JCS:ba <br />(5 copies sent) <br />Enclosure <br />Yours truly, <br />.; 11252 <br />p~ ~W <br />2 <br /> <br />Of <br /> <br />~G <br />`O~QO~ eviewed <br />