became stuck as mining efforts approached some particularly difficult ground. Hand-mining efforts above the TBM shield were eventually employed to free the stuck machine. The tunnel was completed in May 2008 with the installation of pipeline being completed in 2009. Riverside Badlands Tunnel The $119 million Riverside Badlands Tunnel is long, the longest tunnel in the feeder project, with a diameter of and runs from Redlands, underneath the Crafton Hills and San Timoteo Badlands through to Moreno Valley. The tunnel ranges in depth from 50 to 850 feet and contains of pipeline. It has two primary portals; the Gilman portal in Moreno Valley and the Opal portal in Redlands, each with permanent concrete structures. Along with the two portals are two access-ventilation shafts: one along San Timoteo Canyon road and another along Live Oak Canyon road. The tunnel was finished in 2003, a year ahead of schedule. Construction of the tunnel began in October 1998 with the excavation of the Gilman Portal and dewatering work at the two intermediate shafts. Tunnel excavation was carried out from November 1999 through July 2001 using a shielded TBM. Construction of the tunnel included many challenges. The TBM had to bore its way through diverse ground conditions consisting of weak sedimentary rocks; strong, fractured metamorphic rocks; and alluvium, all of which were below the groundwater table. Special measures such as probing and grouting ahead of the TBM and, in particular, deep dewatering wells, were demonstrated to be effective for controlling adverse ground conditions. The project also showed the advantage of working from a portal. The Gilman Portal site proved to be ideal, supporting very efficient mining and muck disposal operations and also allowing long pipe sections to be installed in the tunnel, significantly reducing the amount of field welding required. Notes This article incorporates text from publications of the Metropolitan Water District of Southern California, which is in the public domain. External links Clawing success from the extreme at Arrowhead. www.tunneltalk.com, December 2007 Water supply infrastructure in the United States Water tunnels in the United States