INSIDE ECAlaskan Way Viaduct Electrical Line Relocation Project
The Alaskan Way viaduct runs along the seawall in downtown Seattle and is a major means through which traffic circulates in the city. It is 2.1 miles long and 51 feet wide. About 110,000 vehicles use the existing viaduct each day.
The viaduct has irreparable damage from significant daily traffic, salt air, age, and is at risk in the event of an earthquake. The state of Washington overwhelming approved a series of construction projects entitled “moving forward.” A part of these projects includes the new underground viaduct and power lines to protect the city’s power source in the event of an earthquake. WSDOT, King County, the City of Seattle, and E C Company broke ground on September 12, 2008.
The fist part of the Electrical Relocation project involves moving (2) circuits of 115kV transmission lines and (5) circuits of 15kV distribution lines from under the existing viaduct structure. These lines were installed 32 years ago and are at risk due to environmental exposure. When the new lines are installed in the duct banks the system will not only be protected but the overall load will be increased on both systems.
Working underground presents many different factors to consider. E C has started on the 3,500 feet long concrete encased duct banks, both 6" PVC and fiberglass, for each system. The crew will next install 24,000' of 115kV transmission and 18,000' of 15kV distribution cables from a near by substation to the railroad way transition point. After E C will start removing 6,000 feet of existing overhead oil filled cable, 16,500 feet of existing overhead XLPE cable and removing and replacing the existing oil pressurization system. The new 115kV cable will arrive on 12 individual reels, each one weighing approximately 30,000 pounds! They will be offloaded with a crane onto specially designed stands that can support these monumentous cables.
The project is expected to be completed by January, 2011 and will greatly contribute to keeping Seattle’s traffic moving safety.
Experience the New Via Duct Virtually From Seattle Channel
Learn more at Washington State Department of Transportation