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Attachment A <br />underground monitoring revealed that the seals around the bulkheads in Retorts 7 and 8 <br />were leaking retort water. In addition, increased seepage in the open drifts adjacent to the <br />retorts had begun to appear in some areas. As a result, on July 12's, 2000, the bulkhead <br />valves were reopened and the retorts were allowed to continue to drain by gravity to the <br />Evaporation Pond. <br />It is generally accepted that discharge of the retort water is likely along-term condition <br />without efforts to curtail the source water to the retorts. DBMS suggests a plan of action <br />to either decontaminate the retorts or prevent (or at least minimize) water from contacting <br />spent shale as it passes through the retorts. <br />Since July 2000, OOSI has considered a number of alternative closure options for the <br />mine (retorts) and has also considered other options in response to this adequacy issue. <br />Options considered include: <br />1. Physical diversions of water in the mine <br />2. Bioremediation treatment <br />3. Groundwater barriers (grout or polyurethane seals) <br />4. Intercept drains <br />5. Retort flushing <br />Physical Diversions <br />OOSI conducted a thorough reconnaissance of underground workings before portal <br />closures in the summer of 2003. During this work, it was discovered that the drift areas <br />in the upper level of Retort 8 were flooded. Groundwater was entering the drifr from an <br />electrical conduit borehole adjacent to the main ventilation shaft and pooling on the drift <br />floor around the retort. It was suspected that this water was percolating through fractures <br />in the shale, entering the retort, and contributing to retort water discharge. OOSI <br />constructed a diversion from the conduit to the air shaft through the use of a polyethylene <br />tank and pipe. It is probable that this diversion is responsible for minimizing the overall <br />retort water discharge as most measured flows have been less than 3 gpm since that time. <br />Other groundwater management tasks were implemented to assure that all retort water <br />was contained and conveyed in new HDPE pipe to the main discharge pipeline to the <br />Evaporation Pond. <br />Bioremediation and Passive Biologic Treatment <br />OOSI considered the possibility of in situ and ex situ bioremediation of the retorts and <br />passive biologic treatment of retort dischazge waters. <br />In situ bioremediation treatment of the retorts was not seriously investigated because of <br />the potential risk of poor success due to geotechnical and remedial challenges. <br />Geotechnically, a lazge subsurface drilling program would need to be implemented to <br />characterize the physical conditions of the retorts, followed by extensive sampling and <br />laboratory testing of retorted shale. Laboratory testing would need to include a thorough <br />