Since 1972 many operational and structural problems, including decreasing rotor/stator air gaps and turbine runner blade/throat ring clearances, have been experienced at R.H. Saunders GS. In 1991, concrete expansion due to Alkali-Silica Reaction (ASR), was positively identified as the main source of the problems. To mitigate the effects of concrete growth, a single 15mm (0.6in.) concrete slot covering an area of about 560m{sup 2} (6000 ft{sup 2}), was established in January 1993 with diamond wire cutting. Longitudinal concrete stresses were reduced and equipment clearances were increased in the longitudinal direction. Two additional 15mm (0.6in.) concrete slots were established in April 1994. Production loss was avoided by operating adjacent generating units, while mitigating the effects of concrete growth. Instrumentation measurements that include changes in rotor/stator air gaps, turbine runner clearances, concrete stresses near the throat ring and slot closures are presented in this paper. Results demonstrated that similar trending on equipment clearances and concrete stresses exists among the three concrete slots. Based on the encouraging concrete slotting results of 1993 and 1994, the remaining thirteen slots between generating units are planned for 1995 and 1996. It is anticipated that the concrete slotting will be performed without shutting down adjacent generating unitsmore » provided that the comprehensive equipment monitoring program is in place and existing equipment clearances are adequate. In addition to the concrete slotting program, rehabilitation of structural components that were severely damaged by ASR induced concrete growth is being carried out. The rehabilitation includes the restoration of structural integrity for concrete supports, the installation of sliding supports to accommodate future concrete movements, and grouting of the scrollcases to alleviate leakage problems.« less