San Pedro Creek Tunnel
The San Pedro Creek flood diversion tunnel is approximately 6,000 feet long with a finished inside diameter of 24 feet, 4 inches lined with precast concrete segments. It commences near the Interstate 35-Interstate 10 interchange, between N. Santa Rosa Street on the west and Camaron Street on the east, where an intake approach channel is constructed (See Figure 2 for route). The tunnel inlet shaft is constructed downstream of the approach channel and is 24 feet by 4 inches in diameter dropping approximately 119 feet to the tunnel invert. The tunnel outlet shaft is 35 feet in diameter and contains embedded piping for dewatering facilities.
The tunnel inlet, outlet and maintenance shafts were constructed by conventional methods. The tunnel was constructed using a tunnel boring machine (TBM). The TBM was lowered through the outlet shaft in sections and assembled underground. The TBM bored the tunnel going upstream and in August 1989, the TBM was removed in sections through the tunnel inlet shaft. Excavated materials were removed through the tunnel outlet structure and transported to a disposal site. The tunnel became operational in June 1991.
A subsequent San Antonio River Authority contract added additional pumping capacity for tunnel recirculation. Construction of this phase was completed in June 1997.