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Attachment A <br />location on the surface. Risk is considerably high in the design and implementation of <br />such a system, as even the characterization program needed to support the design could <br />create additional groundwater flow to the retorts through intercepted, water-transmitting <br />fractures. <br />Isolating the retort area from the groundwater system, either by solidification or creating <br />a perimeter barrier would appear to be attractive alternatives. However, these alternatives <br />are also impractical due to the very high costs with serious questions about their <br />effectiveness. Significant additional land disturbance on very steep slopes would also be <br />required. <br />Cost effectiveness and long-term reliability are important factors in addressing water <br />quality of seepage from the retort area. Based on current science, it does not appeaz that <br />either biological treatment of the groundwater seepage from the retort area or attempting <br />to isolate the retort area from the groundwater system aze viable altematives. Ultimately, <br />continued operation of the existing evaporation pond treatment system appears to be best <br />available alternative for addressing the small amount of groundwater seeping from the <br />retort area. Even though this alternative requires a commitment to operate and maintain <br />the system, it is a proven technology that can provide long-term effectiveness with a <br />minimum level of on-going maintenance. <br />Retort Flushing <br />Retort flushing is the process whereby the retorts are repeatedly flooded and allowed to <br />discharge. The flushing process may result in the mobilization and removal of <br />contaminants of concern associated with the spent shale. When the retorts were shut <br />down in the 1970's and 19$0's, they were flushed with water. This process was also <br />tested to a degree during the original Retort Closure Plan (TR No. 1) where the retorts <br />were shut-in and allowed to flood. As mentioned above, this alternative was <br />unsuccessful as the head build-up in the mine resulted in leakage around the bulkheads <br />and surrounding drifts. This alternative is not viable because of the potential unsafe <br />monitoring conditions and release of contaminated water from the mine (in addition, the <br />portals are sealed). <br />Injection of flush water or a surfactant into the retorts through surface-collazed boreholes <br />is also seen as high risk with the potential for clogging retort discharge lines, capturing <br />additional groundwater and diverting it to the retorts, or contaminant release by way of an <br />errant borehole. <br />Other Water Management Alternatives <br />OOSI has considered other management options for the retort discharge water. These <br />include: <br />1. Conventional water treatment <br />2. Underground injection <br />