CONSULTING ENGINEERS AND LAND SURVEYORS OF CALIFORNIA
2008 MERIT AWARD
The 2006 landslide covered the only access road to the powerhouse, and was threatening to send thousandsS of tons of mud and rock into a narrow section of the South Fork of the American River.

The site posed many challenges including a 55 degree pitch and large, open cracks, a telltale signs that the waterlogged soil was still moving and threatened additional sliding. The geological layer under the mud was found to be also highly unstable.

The Carlton team determined that the best fix was to scrape the hill clean of mud, and drill deep to set massive steel bolts 20 feet into the solid bedrock. The bolts connected to large V-shaped concrete beams set across the hill to hold the hill in place. Wire mesh drapery overlaid the slope to prevent the poker chips-like rock, from breaking free.

A latticed concrete crib structure filled with gravel was placed at the bottom of the hill to prevent the toe of the hill from encroaching on the access road along the river. Finally, a separate run-off control system was built to divert rainwater away from the hill and send it down the sides.