Project Connect designs the Lady Bird Lake underground tunnels in detail

AUSTIN (KXAN) — New preliminary designs for Project Connect’s Orange Rail Line detail an underground tunnel at Auditorium Shores, with the track now planned to pass under Lady Bird Lake. Officials detailed the updated plans, pointing to utility and traffic conflicts with the original proposal for a bridge across the lake.

Austin voters approved the $7.1 billion Project Connect plan in the November 2020 election. The initiative details a massive expansion of the city’s transit options.

The proposed Orange Line includes a 20-mile light rail corridor running along Lamar Boulevard and Congress Avenue. The corridor settings extend from Tech Ridge Park & ​​Ride to Howard Lane in North Austin, south to Slaughter Lane.

Peter Mullan is head of architecture and urban design for the Austin Transit Partnership. He noted two potential tunnel options for an underground station at Auditorium Shores, adding that the geological landscape is ideal for a tunnel. Officials said plans involving a surface bridge were dropped due to the following concerns:

  • The vertical ascent from the basement to a bridge lacked feasibility
  • Major utility conflicts (water, sewage, storm sewer, power vaults) near surface between Lady Bird Lake and 3rd Street
  • Federal Emergency Management Agency flood zone hazards near Auditorium Shores, impacting Orange Line tunnel portal

The first tunnel option would resurface above ground south of Nellie Street and Academy Drive and come above ground as it enters the downtown shopping district. Mullan said an above-ground station would be near Lively Middle School, since that area is the first flat place the line comes to, which is necessary for subway stations.

The second tunnel option features a longer underground stay with a re-emergence just south of Leland Street. He said this option would allow for a subway station in the middle of the South Congress shopping district, allowing a bit more flexibility on station entrances and access points.

Key criteria that the ATP always weighs include Americans with Disabilities Act compliance and accessibility, impacts on pedestrians and cyclists, traffic effects and construction costs of each tunnel option.

Mullan said both tunnel options add costs to this part of the project costs, but ATP has built in a degree of financial flexibility for slight changes to the project. He added that the project is still in the preliminary stages, with initial cost estimate updates expected in the coming months.

Bonny J. Streater