As a member of the now defunct Waller Creek Citizens Advisory Committee and a past resident at the Sabine condos with a view directly over the excavation site, I’ve seen planning for Waller Creek evolve over the years.
Earlier this week, Matt Parkerson in Council Member Riley’s office, invited me to join them on a tour of the tunnel. I jumped at the opportunity.
The logistics of mining under a city is fascinating. The tunnel diameter tapers wide from 20 feet to 26 feet in diameter as it approaches the outlet at Lady Bird Lake. The pace of progress is about 15 feet per day. Dump trucks make somewhere around 75 trips per day.
We entered the tunnel between 4th and 5th Streets. Once inside the tunnel we walked to the end of their progress, currently, just below Iron Works BBQ.
Once the mining is complete, the exposed limestone will be coated with concrete. Cost to construct the tunnel: $105 million.
If you’ve ever seen Discovery Channel special on how NYC subways were bored, know this is not like that. There is no giant spinning disc cutting through the earth. Compared to Manhattan granite, this Texas limestone cuts like butter. Like an old dot matrix printer, the boring head cuts away limestone with each back and forth pass.
As an aside: everybody on the tour was thinking the same thing. Why couldn’t we do this for a subway? Well, we can. One of the contractors shared (off-camera) that Austin’s limestone is [actually] perfectly suited for mining a subway tunnel and wondered why the city has not pursued that with more enthusiasm. The length of Waller Creek tunnel is roughly the same length to get from I-35 to Lamar Blvd. An identical tunnel for similar cost could support a subway to traverse east-west through downtown.
Thanks to Council Member Riley and his staff for the invitation!
