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, _ "~y~;+. °.y.-~Y~~~~q(`~~~. tnf I~^ ~''~"~'~s~ ,.+w_3µ ((y'~~' 1 . fin(, ~''~b I1Mr VW "1~'. a~~.1 /Y'~.- ERFOUR ~ ~' ((TT'- Environmental Conseuuences r ~~ ring of water levels in the wells surrounding the mine panel and within the mine °''~0~~ °"~-~ ~ ~~, 'son of water levels to attempt to determine if gradients have been influenced by fluidt ~y ~- the well. ~ ~~ • ampling of the neazby upgradient and downgradient wells in the zone where well integrity ~ '~,.,^%r _~ failure is suspected. }-~- • Comparison of the groundwater analytical data from the baseline and well failure sampling. • Should indications of a failure exist, a monitoring well should be drilled and installed into the impacted zone. If elevated TDS levels are detected, then delineation of the impacts and p/`~~; -~ mitigation of these impacts should be initiated. o c=" The current monitoring plan proposed by American Soda has six of the ten monitoring wells ~^ r, r y~ located in the fast 5-yeaz mining panel (Figure 2-10). No wells az currently I , ~~ ~,• _,,,. downgadient outride the first 5- ear mining panel our wells are located outside the first ~ / °/ Z mining panel. Two of these wells, 19-2 and 2 - ,are located cross-gradient to the panel witltm J '- ' the A-Groove and the Uinta Formation, respectively. We1129-2 is located upgradient of the a panel and is screened at the Dissolution Surface, while we1121-2 is an alluvial monitoring well. ~ ~° Dy None of the wells aze currently co-located. p8`" v' . Additional monitoring is necessary under the action alternatives. To provide adequate detection c,.h' ~ i" _ q of potential loss of production fluids and to determine vertical components of the hydraulic ~ y -rY~ gradient, a network of nested or co-located monitoring wells would be necessary. These wells ~'' . -~ should consist of installations in the Uinta Formation, A-Groove, B-Groove and Dissolution ~ ~_~'~ Surface at one upgradient, two downgradient, and two cross-gradient locations of the first mining 1. panel. To determine the baseline conditions for the aquifers, monitoring of the wells should be undertaken monthly over a 6-month period prior to any mining activity. The monitoring should l+- take place for the pazameters listed in the Mine Plan. Monthly results obtained should be ~a-µ' compazed to the statistical means of the baseline parameter period, and criteria set for further Asa- investigation based upon exceedances. This effort should also be undertaken at each mine pane( / , prior to mining that panel. These efforts should be performed under either action alternative. ~yt : ~ However, the cross-gradient wells may not be necessary except at the first mine panel, de~'ending ~ ~ on what is learned about potential groundwater flow and groundwater quality impacts from the o~"'' ' ~~~.+ (~ initial mining panel. oI~ r'`~~o A potential mitigation measure that could be undertaken as a result of the loss of production fluid ~~~' and the subsequent elevation of TDS in any of the aquifers, would be the installation of extraction wells in the impacted zone and the subsequent recovery of elevated TDS water. This action would apply to either of the action alternatives, if a release of production fluid were to occur. The evaporation ponds at both sites also have the potential to release elevated-TDS fluids into the envirorunent in the event of a liner failure. These ponds should also have periodic inventory and measurement of the fluids to determine the potential for loss. In addition, monitoring wells should be installed at both locations to determine if fluids containing elevated TDS concentrations have been released from these facilities. Groundwater 417 j.