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<br /> <br />52 <br /> <br />1 <br />used to characterize the stream input from the dump. <br />The estimated changes in selected ~,aater quality parameters as the result <br />of deep percolation in a wet year are shov+n in Table 14. Even this worst- <br />case estimate indicates a very small effect on the .+a ter quality in the <br />stream. The sodium adsorption ratio (SAR) downstream of the ~.aaste pile was <br />computed by using the computed downstream concentrations of sodium, calciwn, <br />1 and magnesiurn. <br />' The active ~+aste dump rests on alluvial material directly adjacent to <br />the stream. The alluvium provides a degree of storage, in addition to that <br />in the dump itself, and tends to cause seepage into the stream to occur at <br />a reduced rate, but over a longer period of time. Thus, Che discharge of <br />0.01 cfs from the ~,vaste material, based on a 30 day seepage period, may be <br />larger than actually occurs. The small seep observed during this investi- <br />gation issued from the refuse pile near the contact betvreen the v,aste and <br />the nati•+e ground, and .vas several feet higher than the water table in the <br />alluvium. apparently, the seepage occurred from a water table perched with- <br />in the dump. Evidence of other perched water in the pile v,as not observed <br />and it is believed that the bulk of deep percolation enters the alluvium <br />before discharge to the stream. Figur? 14 compares Che composition plots <br />of alluvial ti•,aters with that in the adjacent stream. The alluvium shows <br />concentrations of sodium and sulfate that are elevated in respect to the <br />stream beyond that attributable to the overall elevated salt concentration. <br />In the case of sodium, a similar elevation was obser~red in the alluvium at <br />the Maxvrell 14ine ~,vhere it was not possible for a reruse pile to have caused <br />the change in composition. Hov,ever, the shift in composition toward in- <br />creased sulfate o-+as not observed elsewhere. Table 13 shows a substantial <br />concentration of sulfate in seepage from the vraste pile and, in all probability, <br />the seepage is responsible for the shift in composition. <br />The elevated levels of sulfate in the v,aste dump are somewhat surprising <br />in view of the fact that all other data on subsurface waters indicate sodium- <br />bicarbonate vraters. There is evidence to suggest that the observed sulfate <br />does not derive from sulfuric acid production from pyrite. Four samples <br />~ of the .caste dump materials '.,ere analyzed for pyritic sulfur, shov+ina only <br />lov+ quantities ranging from 0.03-0.04 percent. Alto, the pH of 8.0, low <br />