The Bypass Tunnel Update, or Is There Light at the End of the Tunnel?

3 Mar 2011 by admin, Comments Off on The Bypass Tunnel Update, or Is There Light at the End of the Tunnel?

So where does Barton Creek go when it gets to Barton Springs Pool?  It disappears into the sidewalk beneath your feet on the north side of the Pool into a structure known as the Bypass Tunnel or BT. In its entire 35 plus year history, it has had little or no major maintenance, has endured countless floods, use and abuse, but still it survives, and looks pretty darn good from the topside. When the Barton Springs Pool Master Plan was created, $250,000 was set aside for maintenance of the BT based primarily on its good looks on the outside.

But go inside the BT and the story changes.  It is then that you realize that it is an aging, cracking, 35 year old leaking tunnel that is full of holes which drain the pool and threaten the salamander. It was clear that the BT was going to need more than a facelift. In 2009 the City of Austin commissioned the engineering firm PKA to develop various options, including total replacement.  FBSP representatives attended many public meetings that year to provide input on the various options until a final option was selected, to the tune of $3.5 million.  Everything seemed to be going fine, when suddenly sometime in the summer/fall of 2010, the City of Austin (COA) pulled the plug on the final option and hit the restart button, do not pass go, go back to square one.
Last December, we met with COA staff to discuss the proposed new concept developed by the engineering firm AECOM.  The new plan was different.  Instead of relying on adding additional concrete and iron to the top of the BT to prevent sliding and floating during a flood event, as PKA proposed in the original plan, the new plan would rely on placing anchor rods through the bottom of the BT and into the rock below and adding a new, heavy concrete floor inside the BT.  The plan would be cheaper by a million bucks, involve less site disturbance, and less closure time for the Pool.  Sounds great! Only one problem: when they drilled a test hole into the fault zone located at the midpoint beneath the BT, they only found mud.  Can’t put an anchor in mud, won’t work, back to the drawing board.

AECOM then developed a plan whereby the fault zone would be bridged by placing steel in the concrete floor, and using sidewall anchors that would not go into the fault, but into the soil on the hillside.  FBSP met with the COA on February 24th to discuss their responses to our written comments concerning the original AECOM plan and to discuss the new plan.  We received written responses to our comments from Watershed at 5 pm on the day before the meeting, and by studying those responses, we were able to narrow the issues for discussion.  FBSP has written a two page memo (pdf) which documents many of the concepts discussed at the meeting.

The upshot is that many of our concerns and questions about the new design have been answered and we support the new design going forward.  However, there are many unknowns: Fish and Wildlife Service approval timeframes, unknowns concerning construction options, length of time for the design approval process, etc.  All of these unknowns could greatly extend the final construction finish date.  This is frustrating because we originally thought the BT repair would be occurring at the same time as the gravel bar removal project which is almost finished.  However, the dedicated FBSP board members will continue to be involved with the COA staff to make sure the concerns of you, the members of FBSP, are heard and problems are resolved.  Even though it has about as much light as a twinkling star in a downtown Austin night sky, there is a light at the end of the tunnel.  We will go to the light!

-Gary Beyer
Vice President, Friends of Barton Springs Pool

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