Field Fabricating a Lake Tap 108 inch Outlet to Vertical Shaft 230’ Beneath Lake Travis


ABSTRACT; Field Fabricating 108” Lake Tap Outlet to 108” Vertical Shaft which is 230’ beneath a Lake is the focus of this slide show which includes photographs and detailed descriptions. Lake Travis is located northwest of the City of Austin, Texas.  Due to explosive population growth in the area, the Austin Water Plant No. 4 was designed and constructed in the “hill country” to pull water out of the lake through an intake vertical shaft and tie-in the tunnel located approximately 230’ underneath the lake.  The project was designed and bid with one contractor doing the shaft and another installing the tunnel and Cut-In Outlet.

This slide show discusses from a specialty installation and manufacturer perspective how and why the cut-in outlet was required for this installation between the Intake Shaft and Tunnel. Also discussed is how a standard AWWA Manual M11 Design Procedure for Crotch-Plated Fittings in the original bid documents was not applicable for this installation.  The paper will go into the design procedure and methodology used and discusses the changes that took place between the design and approval process and the final installation.  The first half of this paper will discuss the Pipe Manufacturer’s Perspective including the design, bid and approval process for this installation.  The second half of this slide show will be the Specialty Installation Perspective which will discuss the installation process including the outlet fit-up, welding and NDE practices used for this installation.