Into the bedrock: Capital Metro plans to go below Lady Bird Lake with Orange Line tunnel
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Project Connect’s Orange Line will run under Lady Bird Lake in the latest design. (Rendering courtesy of Project Connect)
Trains running between the planned MetroRail stations in Republic Square and Auditorium Shores will enter the bedrock beneath Lady Bird Lake in accordance with the latest Project Connect design.
Since a bridge is not feasible, the Austin Transit Partnership is advancing plans to build a tunnel under the lake. Officials said these plans are still 15% complete and could change as the planning process progresses.
At its deepest point, Lady Bird Lake reaches about 18 feet, according to Texas Parks & Wildlife. To ensure that the tunnel is safe, it must be submerged within the bedrock as per the Austin Transit Partnership’s plans.
“In the alternative analysis phase, we expected that crossing the Orange Line across the lake would be a bridge,” said Peter Mullan, Austin Transit Partnership head of architecture and urban development. “When we got into the preliminary planning and examined all parameters that would influence the route of the Orange Line at this location, we discovered that there were various potential conflicts with a bridge at this location.”
Due to the floodplains on Riverside Drive and Bouldin Creek and busy intersections, the tunnel will not appear immediately after the Auditorium Shores stop, which would be underground. In addition, the analysis found that building a bridge would require 2nd Street to be closed to traffic and create supply conflicts from 3rd Street to Lady Bird Lake.
The Austin Transit Partnership offered two possible tunnel exits: the short tunnel would be near the intersection of South Congress Avenue and Nellie Street, and the long tunnel would be near South Congress Avenue and Leland Street. The Leland Street exit would mean that South Congress Station would be underground near Elizabeth Street.
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In comparing the two options, the Austin Transit Partnership said the long tunnel provides better access to buses, a better location for the train station, and fewer changes in traffic patterns.
However, the analysis also said that the long tunnel would be “significantly more expensive due to the length of the tunnel and the underground train station”. The Austin Transit Partnership Board of Directors reiterated this opinion when they reviewed the network of proposed subway stations.
“We also need to understand that every time we go underground, the cost increases exponentially,” said Tony Elkins, board member of the Austin Transit Partnership.
As for Republic Square, officials said the inability to build under the square because Texas state lawmakers failed to pass House Bill 3893 won’t detract from the overall design of the downtown area. Instead, the station is moving further north, closer to the busy Sixth Street.
“I think it was really good muscle strength for us to have to work in some ways,” said Mullan. “There will be challenges during this process, things that come up, we have to figure out how to work around them and solve them for them.”
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