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<br />...... <br />a.l <br />QO <br />~ <br /> <br />a reasonable ass~~ption for a large portion of the Piceance Creek BaBin of <br />Colorado. In addition, we have shown in Table 4-3 a net output of mine <br />drainage water in an amount consistene with the expec~ed drainage waters <br />from the C-a and C-b oil shale sites. The trea~~ent or handling of e~cess <br />groundwater, a situation which could also occur with mines for surface <br />retorting, will be discussed in ~~e ne~t section. <br />Figure 4.1 shows the major parts of a water management scheme for a <br />modified in situ oil shale plant with a product mi~ and watar balance <br />characterized by Table 4-3. ~.o important features in the water management <br />are that the foul retort water ~rQduced is in excess of the water requirement <br />for the cooling tower, and the mine d~ainage water, which p~ovides t~e water <br />for the plant, exceeds ~~e plant needs. Figure 4.2 is a simplified diagram <br />of ~he erea~ent path for ~,e mine drainage water, where the water in ~xce5S <br /> <br />of the plant needs must be treated for Cisposal. <br />For the water ~anagement scheme of Figur~ 4.1 a~d the water bala~ce of <br />Table 4-3, we ~ave shown in Figure 4.3 a si~plified water treatment flow <br />diagram for a modified in situ plant producing 57,COO bbls/day of shale oil <br />and 300 MW of electricity by a combi~ed ~fcle system. ~ote ~~a= the streams <br />co not balance around ~,e retorting and gas cleaning section in part because <br />water is generated in the retorting and water appears as hydrogen in the <br /> <br />retort off-gas. <br /> <br />!~ canr.ot be emphasized too strongly that ~'e trsa~ent <br /> <br />flow dia;ram is sL~ply illustrativel with its pUr?ose to place the ~reatrnent <br />procedures in perspective *i~~ regard to sequence and quantities hancled. :~ <br />the sections which fallow, we shall we shall discuss each of the individual <br /> <br />waste streams. <br /> <br />4.2 Excess Mine Drainaae Water <br />In the preceding section we have provided some estimates of ~~e quantities <br />of excess mine drainage water that may be expected in the rncdifiec in situ <br />processing of oil shale in ~~e Piceance Creek 9asin. It has generally been <br />assumed that the quality of the mine drainage water will closely resemble the <br />water in the aquifer that is drawn down (Ref. 4 (Vol. 3) and Ref. 7). This <br />can be exp~cted to be true so long as the groundwater does not contact or is <br />not stored in contact with freshly rubblized raw shale. If the wa~er coes <br />contact freshly exposed shale, contaminants, ?artic~larly organic acid <br />salts, may be leached out. The extent of ~~e leaching may be depencent on <br />the water volume, contact time with ~~e raw shale, susgended shale solids in <br />the water and o~~er factors. Because sufficient data is not available at <br /> <br />this time, ~e have to assume that the mine d~ainage water is charac~erized by <br /> <br />t~e aqui=er water. Infornation en this important point is needed. <br />