RBOSC proposes to abandon the two modified in situ retorts on Tract C-a in the following manner: pump existing water out of retorts, allow retorts to flood completely, recirculate water through retort to leach most of soluble material from the rubble, pump all leachate from the retorts and product collection system, flood retorts, and monitor groundwater in area around retorts until it has been determined that an unacceptable migration of harmful substances is not likely to be detected in the monitoring wells adjacent to the retorts.