The San Antonio River flood diversion tunnel is approximately 16,200 feet long with precast concrete segmented liners of 24 feet by 4 inches inside diameter. The tunnel starts near Josephine Street where the tunnel inlet shaft is constructed adjacent to the existing channel (See Figure 2 for the tunnel’s route). The inlet shaft is 24 feet by 4 inches in diameter dropping approximately 118 feet to the tunnel invert. The tunnel outlet shaft near Lone Star Boulevard is 35 feet in diameter and contains embedded piping for dewatering facilities.
The tunnel intake shaft is located between West Josephine Street and Highway 281 North (See Figure 3 for profile of the San Antonio River Tunnel). Borden’s Dairy is on the west side of the river and a small manufacturing plant is located on the east side of the river.
The tunnel outlet structure is located south of the Southern Pacific Railroad, north of Lone Star Boulevard and west of the river.
Construction for the San Antonio River Tunnel Inlet Structure started in September 1993. The contractor, BRH Garver, constructed a water feature, park facilities, betterments, channelization and tunnel recirculation for the flood control tunnel. A pumphouse was also constructed, mostly below ground level to operate pumps to recirculate tunnel water to supplement river flow during the summer months. This project is a coordinated effort between the U.S. Army Corps of Engineers and the San Antonio River Authority. The Corps bid the project on behalf of the River Authority. Total construction cost was $16.9 million.
Notice to proceed for the San Antonio River Tunnel Outlet Structure was given to Martin K. Eby Construction Company, Inc. on May 5, 1995 and the project was completed in December 1997 at a total cost of $10.1 million. This project includes a water feature, a galvanized steel trellis over a pedestrian plaza, park facilities, betterments, channelization and a gatehouse for tunnel water recirculation. The project was jointly administered by the U.S. Army Corps of Engineers and the San Antonio River Authority.