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CNAPTERFOUR Proposed Action Piceance Site Consequences Under the proposed 30 yeazs of mining, a significant impact to groundwater would be an accidental release of production fluids or migration of these fluids into the Uinta Formation portion of the Upper Aquifer. Production fluids could potentially be introduced to this aquifer from casing leaks, from the migration of poor quality groundwater from the Lower Aquifer, or from leakage from the onstte evaporation pond. As presentee to 5~ecuon 3.4, the total dissolved solids (TT)S) of the Uinta portion of the Upper Aquifer is typically less than 1,000 mg/l. Data t L collected by American Soda in the vicinity of the experimental mine site indicated that TDS in ;~_+ ~j 'the Uinta portion of the Upper Aquifer ranged from 944 to 2,980 mg/1. TDS in the Pazachute ~;~ Creek portion of the Upper Aquifer exceeded 10,000 mg/1. The groundwater in the Uinta `~ `~ ~' Formation is classified by the Environmental Protection Agency (EPA) as an underground source :~~ of drinking water (USDt~. The Upper Aquifer could be impacted if a release of production fluids from the well casings occurred directly into the Upper Aquifer. Potentially, this release would be the result of a well casing failure..A release of this nature would result in the degradation of the aquifer by the addition of higher-TDS production fluids being introduced into the lower-TDS water of the ~ aquifer. Quantification of the impacts from a casing failure is not possible because flow rates jlarid fluid concentrations associated with this type of event cannot be readily predicted. However, ^~ American Soda's drilling, casing, and well testing/monitoring program should minimi~r the v occuaence of well failures; therefore, the probability of a lazge volume release of high TDS production fluid into the aquifer is believed to be low. f ,.. .i Poor quality groundwater could potentially migrate from the Lower Aquifer if conditions either " ' ' ~~ exist or are created through the injection of fltiids that introduce an upward hydraulic gradient. ~,^ `~ ': ~i;Jpwazd gradients exist when the differential pressure (head) between two aquifers is such that ..,'~ Q ~~ •.•. ~ ~`fluids have the potential to migrate from the Lower Aquifer (higher head) to the Upper Aquifer ,~ v; r~`' ~, ~ir~:' (lower head). This differential pressure could be induced either by mining solution leaking from s .; ` ` •• ` the cavity along a fault or fracture zone or by the gradual loss of fluid from the casing of the ors ~t ~a ;~.~. '•~ wells. ~ . In the case of atining cavity leaking along faults or fractures, this may cause enough disturbance r in the aquifer to diffuse aplume ofhigh-TT)S fluid and result in a pressure differential between the aquifers. Should a casing leak within the production wells remain undetected for a protracted period of time, the resulting volume of fluid could also result in a change in the differential pressure of the aquifers and the subsequent migration of poorer quality water from the Lower Aquifer into the Upper Aquifer. Quantification of the impacts associated with either leakage of fluid from the mining cavity or from the loss of solution from a casing leak into the Lower Aquifer is not possible because the flow rates and fluid concentrations cannot be predicted with any certainty. However, potential low volume releases of high TDS production fluids from the solution mine cavities (e.g., along fractures) would not likely cause significant impacts to groundwater quality in either the Upper or Lower aquifers if detected and mitigated quickly through American Soda's well pressure monitoring program. Americart Soda also believes that ~ potential leakage of high temperature, saturated brine from a solution cavity would cool rapidly 4-14 Groundwater