The Challenge
A deep seated landslide covering over 250 acres threatened Hwy 80 near Fairfield , CA. CALTRANS contracted with Condon-Johnson and Associates (CJA) to install a large diameter shaft which would house horizontal drains to drain the slide plane of the moving soil mass.

The Solution
The shaft and drains together are known as a “Rainey Drain”. CJA excavated the shaft at a diameter of 6 meters to allow access in the shaft for the horizontal drain drilling equipment. The shaft was excavated in sandstone, melange and basalt formations by excavation and/or drill and blast methods to a depth of 91 meters and secured with a shotcrete lining as it was advanced.

The Result
204 horizontal drains were installed at three levels in the shaft. The resulting drainage, which moves up to 80 gallons of water per minute, is successfully relieving the pressure on the slide plane.

The $ 8.8 million contract was performed in a thirty-month period.

Featured Expertise:

Heavy Civil Engineering