Bonneville Power Administration

Grand Coulee 500kV Cable Replacement Project, WA

Work included removal and disposal/recycle of 525kV self-contained fluid-filled cables, reservoirs, appurtenances and insulating oil. The 525kV cables began at the 500kV Spreader Yard and ran through two tunnels to the Third Power Plant (TPP) located at the base of the Grand Coulee Dam. Each tunnel contained three circuits (9 cables plus ground wire) totaling 6,400 feet. Challenges included limited access to the tunnels, overcoming a 600-foot elevation change with a 30-degree-plus incline, working in energized yards, and the constant management/handling of the used residual oil in the cables. The unique nature of the work coupled with the physical constraints required the development of custom machinery to work within the tunnels in order to remove cable safely and efficiently.

Wilson's responsibilities included development of an SWPPP, an Emergency Response Plan, a detailed project Removal Plan, and a Site Specific Safety Plan which took a collaborative effort by Wilson's environmental, safety, project management and field construction groups. The successful removal for the cable system in its entirety consisted of 21.5 miles of cable, clamps, ground wire, supports, oil storage tanks, surge arrestor(s), degasifier(s), cable oil pressurizers, thermo units fan units, tunnel re-coolers. Work was completed six months ahead of schedule.