Wawona Tunnel Electrical System Replacement

Yosemite National Park » Wawona Tunnel Electrical System Replacement » Document List

• Replacement of the overhead electric line serving Wawona Tunnel and Turtleback Dome communications/data facilities.
• Replacement of the overhead electrical distribution system with an underground high-voltage duct bank (under Southside Drive/Wawona Road roadways from Pohono Bridge to approximately 3,200 feet from the tunnel's west end and approximately 1,100 feet overland on Turtlebank Dome slick rock).
• Construction of an emergency power source facility on the west end of Wawona Tunnel, and demolition of the one mile of existing overhead power lines and poles via helicopter.

Purpose and Need:
• Significant drops in voltage levels are common in the Wawona Tunnel electrical distribution system, creating an unreliable power supply for proper operation of a new tunnel ventilation system.
• The electrical distribution system is the only commercial power source for the current park telephone and radio communication hub on nearby Turtleback Dome. The unreliable power it delivers jeopardizes the park's ability to provide timely response to fire, medical, and law enforcement emergencies.
• The existing electrical distribution system transects one mile of mountainside (overhead lines and poles from the Valley substation to the Wawona Tunnel and Turtleback Dome cutoff), providing a visual intrusion and disturbing the natural conditions of the area.
• The Wawona Tunnel (including Turtleback Dome facilities) currently has no backup power generator. When power outages occur, there is no ventilation or lighting throughout the tunnel.

Installation of the wood-sided generator building would require a concrete pad measuring 14 feet by 22 feet by 4 feet. The underground diesel tank requires an area measuring 5 feet by 14 feet by 8 feet and associated trenching to the generator building. The utility line requires trenching 2 feet by 4 feet deep by 3,200 feet along the road prism.

This project is not in the Merced River corridor.