SAK, in joint venture partnership with Quest Civil Constructors, Inc., was awarded this project on 02/15/10. This project, being completed for the City of Austin, consisted of 19,950 lf of both soft ground and rock tunnel construction. Four access shafts with diameters of 20 feet were also excavated. Secant piles were installed to provide shaft support down to the rock interface. A Webster rock excavator along with rock bolts for support was used to excavate the remaining rock portion of the shafts down to tunnel invert.
Three separate tunnels were excavated on the project; the Comel Leg at 6,453 lf with a diameter of 121 inches, the Riverside Leg at 6,878 lf with a diameter of 121 inches, and the Toomey Leg at 5,270 lf with a diameter of 83 inches.
After completion of tunnel excavation, three different diameters of Hobas pipe were installed as permanent tunnel lining; 54 inch, 78 inch, and 90 inch. Hobas pipe was installed within the tunnels with specially designed hydraulic pipe carriers. Once installed, backfill grout was placed within the annulus between the pipe and tunnel wall.
Since the commencement of the work, additional work scopes have been added to the contract by the Owner, consisting of an additional 1,349 lf of 83 inch diameter tunnel excavation with 36 inch diameter Hobas pipe, three new manholes, two additional live tie-ins, and the changing of the access shaft linings to polymer resin concrete.