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,- <br />iii iiiiiiiiiiiii iii <br /> <br />INTERNAL MEMO <br />TO: Sandy Brown <br />a <br />FROM: Jim Bumel ~ fM'` <br />SUBJ: Edna Anttlfal Hydrology Report <br />May 24, 1999 <br />dy, I have reviewed~P&jM~',s 199y8~[AHR for Edna. There aze no bNi~g,issues. _ . _ <br />~x~+:7~~-:.~n`om. ..LS~4yp,.[^.Er~:!xVti:v~#~`1... `, 'Y"ir=~ :'.,~'~~LIM.:c~i'i~}%.k~'ti;'~'. '-`:: .x~~hT. <br />On page 27,~ P&M states that one should exercise caution in interpreting groundwater chemtstry -.. "~~ ' <br />because of the position of various alluvial wells relative to stratigraphy. I don't remember seeing <br />such a "note of caution" before and I am curious as what affect the author has in mind. Is the author <br />implying that the contribution of dissolved constituents from different bedrock units would be <br />sufficiently significant to affect the overall geochemistry of the alluvial water? I am not sure what <br />the author is getting at. <br />2. Given the use of data from NPDES dischazge points in the calculations ofsalt-loading in the permit <br />(Appendix 2.5-A), these data should be included in the AHR, a practice which hasn't been done in <br />the past. <br />3. A good bit of the PHC is dedicated to water balance issues (surface run-off vs. groundwater); it's <br />difficult, if not impossible, to make any meaningful observations on those issues from monitoring <br />data. <br />4. Recalling the surprisingly high TDS concentrations in well TRI.S, upgradient of the mine, it is <br />interesting to note that those concentrations have remained relatively steady, maybe diminishing <br />slightly. We agree with P&M's discussion that the cause for the increased salinity is unknown, but <br />certainly that high-salt groundwater will be migrating down-gradient and impacting the other alluvial <br />wells in a couple yeazs. Already the groundwater at the West Ridge well, Wr-1, exceeds the <br />predictions of the PHC, so that, combined with the saline water contribution from unknown sources <br />upstream will make a difference on that alluvial aquifer for a long time. <br />5. P&M's predictions of the TDS impacts on Trout Creek appeaz to correspond with the recent <br />calculations in Appendix 2.5-A. The maximum in-stream TDS contents neazly always occur during <br />April as discussed in the text. Streamflow has not reached its peak at the same time a lot of saline <br />water is washing out of the spoil springs from snowmelt infiltration. A plot of TDS vs. flow shows <br />that in '96, '97, and '98 the big spikes in TDS at the downstream monitoring point occur in April. <br />