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The Battery Street Tunnel in 2009. Courtesy of WSDOT
Potential projects ranged from a mushroom farm to sustainable wastewater infrastructure. But after a City Council vote Monday afternoon, there’s only one thing that can happen to the tunnel: It will be filled with rubble and sealed off.
Source: The Battery Street Tunnel will become rubble storage, not public space – Curbed Seattle

File photograph of the Battery Street Tunnel in Seattle during the viaduct’s semiannual inspection in 2009. Credit: Washington State Department of Transportation
A mini design competition, titled Recharge the Battery, brought a rich collection of ideas for reusing the tunnel presented in September at a neighborhood space called Block 41 in Belltown. …Over 40 display boards showed how the underground structure could be put to work. Some of them believe it could be a great place for a park, a thrill ride, or maybe a combination of the two.
Source: Mushroom farm? Park? Oh, the possibilities for this Seattle tunnel
Reclamation Administration: News and Research on Building Material Waste Prevention