from the Nisqually earthquake up until the viaduct was removed in 2019. Due to damage from continuing settlement, a group of researchers and faculty from the University of Washington urged the mayor of Seattle (in 2007) to close the viaduct within a four-year timeframe. Tunnel planning and construction On January 12, 2009, the governments of Washington, King County, the city of Seattle, and the Port of Seattle announced that they had agreed to replace the viaduct with a four-lane, long tunnel. The tunnel would have a south portal in SoDo, near CenturyLink Field, and a north portal near Thomas Street, north of the Battery Street Tunnel. The project was estimated to cost $4.25 billion, with state, city, and county promised funding well short of the estimate. The state would fund boring of the tunnels, while the city and county would fund surface street improvements and repairs to the Alaskan Way Seawall, which itself was damaged in the Nisqually earthquake. The announcement did little to quell the long and heated debate over the viaduct's replacement, with several factions expressing their criticism over the tunnel decision. Boring of the tunnel by the tunnel boring machine "Bertha" began on July 30, 2013, with the roadway initially scheduled to open in December 2015. Tunneling stopped on December 6, 2013, after the boring machine struck a steel pipe, which obstructed its path into the route. Investigations revealed that the machine had struck a pipe which had been installed in 2002 as a part of an exploratory well used to measure groundwater as part of the planning phases for the project. Boring resumed briefly on January 28–29, 2014, stopping again due to damage to the seal system which protects the machine's main bearing and damage to several of the cutting blades. This caused a two-year delay as it was necessary to dig a vertical shaft recovery pit from the surface in order to access and lift the cutterhead for repair and partial replacement. Work was initially expected to resume by March 2015, but it was December 2015 before tunnelling recommenced. Boring was halted again 23 days later after a sinkhole developed on the ground in front of the machine, but resumed a month later. In July 2016, a citywide ballot measure attempted to build an elevated park along the waterfront after the demolition of the viaduct, utilizing a portion of the existing structure. The attempt failed,