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Permit Renewal Figure 4, Triangular Diagram Plot, Backfill Groundwater. The extent of groundwater effects is <br />influenced by the rate of groundwater movement in the undisturbed aquifers, the relative contribution of <br />~routtdwater from disturbed areas as compared to total aquifer recharge and storage, and the cumulative effects of <br />dilution and dispersion. The potential impacts will be discussed in more detail under Probable Hydrologic <br />Consequences. <br />Recharge to the Trout Creek Sandstone aquifer through overlying disturbed areas may also impact water quality <br />locally. The Trout Creek baseline water quality is asodium-bicarbonate type and has a typical TDS cottcen[ration <br />of about 900 mg/I. The extent of the effects is primarily controlled by the vertical permeability of the interval <br />separating the backfilled material from the Trout Creek Sandstone. The potential impacts will be discussed in <br />more detail under Probable Hydrologic Consequences. <br />The water quality of groundwater in the alluvial deposits may be affected indirectly, if ilte water quality of creek <br />flows are impacted as a result of discharges from disturbed areas. Tltis is discussed further under Probable <br />Hydrologic Consequences. <br />Groundwater Protection and Mitigation Measures <br />• <br />Standard operation and reclamation practices utilized in the Eckman Park, Mine 1, and Mine Z operation areas are <br />described in detail in the response to section 780. Those practices which were significant with respect to <br />prevention or mitigation of groundwater impacts include the following: <br />• Minimization of the area disturbed <br />• Direct sidecasting of spoils <br />• Gravity drainage of pumping or water accumulations in the active pit to surface retention structures <br />• Contemporaneous reclamation <br />Mining, reclamation, and related activities were carefully planned and sequenced to limit areal disturbance attd <br />minimize potential <br />• <br />1996 Permit Ren. Permit Renewal 780-144-2 Revised 3/18/97 <br />