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• • iii iiiiiiiiiiiiiiii <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />Phone: 1303) 866-3567 <br />FA%:1303) 832-8106 <br />December 28, 1992 <br />TO: Susan Morrison <br />FM: Shawn Smith< <br />Re: Annual Ground Water <br />Dear Susan: <br />ov ~o<o <br />~~_~ <br />~e ~ ~ o <br />.~. <br />~ rB ]6 <br />Roy Romcr <br />Governor <br />htichael8 Long <br />Division Dneaor <br />Hydrology Review for Senaca II (C-80-005) <br />I have reviewed the 1991 (submitted February 1992) Annual Hydrology <br />Report from Senaca II. In addition, I have also reviewed the <br />following documents: <br />Findings Reports: 11/31/86 and 11/12/92 <br />Midterm Review: 01/17/90 <br />Permit: Sections on Ground Water, PHC and Geology (Tabs 5 & ~ <br />Technical Revisions <br />Minor Revisions <br />Stipulations <br />Jeff Martin memos: dated 7/15/92 and 08/05/92 <br />PARAMETER CHECK <br />All ground water wells in the permitted area were reviewed for <br />stock/irrigation recommended standards except for one case; well <br />GW-S5-TC which was analyzed for domestic use standards. <br />Electrical conductivity values (conductivity values associated with <br />salt content) were high in all wells. However, the relationship <br />between EC and TDS was within limits, TDS never exceeding the 5000 <br />mg/1 standard for irrigation purposes. It is necessary to mention <br />that according to Jeff Martin's memo dated July 15, 1992, ground <br />water is not being pumped for "either irrigation or stock <br />watering." Only one well; GW-S5-TC is used for any beneficial use, <br />primarily domestic use on the mine site. In general, most wells <br />showed an increase in TDS, but all still remained within the 5000 <br />mg/1 limit. Three wells in particular should be watched for <br />further increases over time in TDS levels: GW-56-A, GW-S31-A2, both <br />in Little Grassy Creek Alluvium and well GW-S68-A in an unnamed <br />tributary to Fish Creek. These three wells show a steady increase <br />in TDS and are part of alluvial valley floor system for Fish Creek <br />and eventually the Yampa River system. An additional well, GW-S17- <br />W in the Wadge Coal seam, also appears to show a steady increase of <br />TDS and should be carefully monitored in 1993. Curiously, all the <br />spoil wells showed a decrease in TDS from 100 to 200 mg/1 from 1990 <br />to 1991. This may be due in part to low precipitation levels <br />