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The Inland Feeder is a 44 mi (71 km) high capacity water conveyance system that connects the California State Water Project to the Colorado River Aqueduct and Diamond Valley Lake. The Metropolitan Water District of Southern California designed the system to increase Southern California's water supply reliability in the face of future weather pattern uncertainties, while minimizing the impact on the San Francisco Bay/Sacramento-San Joaquin Delta environment in northern California. The feeder will take advantage of large volumes of water when available from northern California, depositing it in surface storage reservoirs, such as Diamond Valley Lake, and local groundwater basins for use during dry periods and emergencies. The project also will improve the quality of Southern California drinking water by allowing more uniform blending of better quality water from the state project with Colorado River supplies, which have a higher mineral content.

Geography

The feeder begins at the Devil Canyon afterbay in the foothills of San Bernardino and makes its way through the Arrowhead West and Arrowhead East tunnels into Highland. From there the Highland pipeline and Mentone pipeline carry water to Redlands and the northern end of the Riverside Badlands Tunnel. The Riverside Badlands Tunnel runs south into Moreno Valley where a series of pipelines carries and deposits water into Diamond Valley Lake near Hemet.

Construction

Arrowhead West Tunnel

The Arrowhead West Tunnel is 3.8 mi (6.1 km) long and 12 ft (3.7 m) in diameter. The tunnel begins at Devil's Canyon and is the first of the three tunnels in the feeder project. It continues east to the Waterman portal at Old Waterman Canyon Road and State Highway 18. The tunnel was constructed with a grade to allow water to flow by gravity, from the time the water enters the Devil Canyon Portal until it exits the Waterman Portal, the tunnel will have drops about 31 feet in elevation.

The west tunnel was the most difficult of the three tunnels to excavate. It was excavated using a Tunnel Boring Machine(TBM) that took over four years to bore it's way through the mountain. The TBM was launched from the Waterman Portal and tunneled in a westerly, uphill direction toward the Devil Canyon portal at a slight uphill gradient of approximately 2 inches per 100 linear feet. Crews faced many challenges during the excavation including the 2003 Old Fire which destroyed construction equipment at the Waterman Portal and halted tunneling for ten days. Later that year a flash flood engulfed the Waterman Portal site and submerged the TBM. It took four months to restore operations in the aftermath of the flooding.

The TBM faced many challenges during the tunneling. Much of the tunneling took place in water-bearing strata of metamorphic and granitic rock. The presence of water, coupled with the depth of the tunnel, up to 1,100 feet underground, forced the tunneling team to deal with water pressures in excess of 150 pounds per square inch. Additionally, the tunnel alignment crossed or traversed near several significant faults and shear zones, including branches of the San Andreas and Arrowhead Springs Faults. In these faulted areas, the massive blocks of rock were broken into fine debris that were treated with grout before tunneling could safely cross through these zones. A particularly challenging reach of the tunnel alignment was encountered in the last 1,500 feet of the tunneling work as the TBM crossed five significant fault/shear zones along the tunnel alignment on its way to completion at the Devil Canyon Portal. While tunneling in this zone in mid-2008, the TBM began dipping as it encountered a 40-foot wide fault zone of completely crushed, weak rock. Concrete and steel foundation pads were constructed in front of the cutterhead to stabilize the TBM and correct the alignment of the machine as it crossed the weak ground within the fault zone. The tunnel was completed in August 2008 with installation of pipeline being completed in 2009.

Arrowhead East Tunnel

Riverside Badlands Tunnel

The $119 million Riverside Badlands Tunnel is 8 mi (13 km) long, the longest tunnel in the feeder project, with a diameter of 12 ft (3.7 m) 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 1,500 feet (460 m) 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.

Easternmost in the IFP, the Arrowhead East Tunnel Project includes 1,500 linear feet of 12-foot-diameter (3.7 m) welded steel pipe installed in a trench connected to a 30,000-foot tunnel through the San Bernardino Mountains. The tunnel lies up to 2,000 feet (610 m) below ground in some locations. This tunnel is linked into the California Aqueduct, which conveys water from Northern California as part of the State Water Project. (citation needed)

The Arrowhead West Tunnel involved the construction of a 12-foot-wide (3.7 m) tunnel 21,175 feet (6,454 m) long connected with 6,630 feet (2,020 m) of buried pipeline. The tunnel generally runs along Old Waterman Canyon Road and State Highway 18 in San Bernardino County, California. Seismic faults crossed by the tunnel include the Arrowhead Springs Fault, near the North Branch of the San Andreas Fault.

Geological issues such as fault zones and water table depths ended up adding to the length of time needed for construction, as did several natural disasters. In 2003, the Old Fire caused damage to construction site, which was further damaged by subsequent flooding in late 2003. Legal issues over water rights and also geotechnical issues arising from traversing earthquake fault zones also added to the delays. According to the Metropolitan Water District, around 2002 a “bolt and gasket system similar to that used on the Chunnel that connects England to France” was employed to reinforce concrete tunnel segments where water was leaking into the site. Delays notwithstanding, on August 17, 2008, the tunnel-boring process was completed with much fanfare. Completion of the tunnel infrastructure and the rest of the IFP is slated for late 2010.

Notes

1. ^ "Inland Feeder Project... at a glance". Metropolitan Water District. July 19, 2007. Retrieved 2010-09-20.
2. ^ "Inland Feeder" (PDF). Metropolitan Water District. September 10, 2008. Retrieved 2010-09-20.
3. "California Inland Feeder Project". Mott MacDonald. Retrieved 2010-09-20.
4. ^ Arabshahi, Jay (2003). "RIVERSIDE BADLANDS TUNNEL, INLAND FEEDER PROJECT: THE CHALLENGES BETWEEN CONCEPT AND COMPLETION" (PDF). Jacobs Associates. Retrieved 2010-09-20. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
5. EPC, 2007. http://www.epcconsultants.com/Inland%20Feeder.html
6. (EPC, 2007). http://www.epcconsultants.com/Inland%20Feeder.html
7. Bowles, Jennifer. “Tunnel Adding Key Link to MWD’s Inland Feeder Water Project.” Press-Enterprise, Aug. 20, 2008 http://www.pe.com/localnews/inland/stories/PE_News_Local_S_tunnel20.495b60a.html
8. Bowles, 2008
9. Brennan, 2008.
10. MWD, 2007.

• Water supply infrastructure in the United States