This project was a firm-fixed contract to replace 18 failing Medium Voltage switches with new S&C Vista SF6 Switches. Peachtree sub-contracted with I.C. Thomasson Associates in Nashville,TN to assist with the design of the project, to review submittals for accuracy, and to develop anew one line drawing upon completion. The Electrical Division of Peachtree Mechanicalmade several trips to the facility to gather information for I. C. Thomasson for designproposes, measure existing pads, and to meet with the S&C representatives to assure that allswitches would be the correct size and configuration (2-way, 3-way, or 6-way) and to confirmthat the new Kirk Key Interlock system was correct. Since this was an occupied facility, power had to be always maintained to all buildings. This was accomplished using 850 KW and 1 MEG generator sets. Peachtree Electrical designed special copper bars with drilled holes that lined up with the holes on the spades in the transformers. The generator leads were attached to the copper bars which minimized the load transfer times. Each switch had to be isolated from the redundant loops, and the leads from the generator terminated to the secondary side of the existing transformer to maintain power to the building. After all this was accomplished, the old switch was removed, the new switch installed,cables terminated, and the new switch energized. The generator leads were removed, andthe transformer was energized. This procedure was repeated 18 times with no incidentsreported.The United States Penitentiary at the Federal Correctional Complex in Yazoo City, MS is anoccupied high security facility. NCIC clearances were required to enter this facility and securitychecks were performed each day before entering and leaving the facility. All tools and equipment were checked into and out of the facility. The Electrical Division of Peachtree Mechanical completed this project as scheduled.