Sonoma Mountain, Mendocino County

Tire Derived Aggregate as Landslide Remediation/Slope Stabilization

The Sonoma Mountain Road project site is located in Sonoma County in the town of Glen Ellen. This was the second of two projects that partnered Sonoma County and the California Integrated Waste Management Board (CIWMB) (now the Department of Resources Recycling and Recovery, or CalRecycle) in an effort to expand the county’s knowledge and use of tire-derived aggregate (TDA) in slide repair projects. During this project the county used the knowledge it had learned from the design assistance the CIWMB previously provided for Geyser Road slide repair project to design and implement a similar repair here using County resources.

Previously, approximately 600 feet of Sonoma Mountain Road failed due to a landslide, requiring the slope and roadway to be reconstructed in the 1980’s. The landslide was caused by a combination of weak native soil and excess ground moisture (saturated conditions).

Sonoma Mountain road failure with crumpled metal railing

Sonoma Mountain road failure.

Sonoma County had initially designed the repair of the landslide-damaged road section using a retaining wall approach. The County constructed a 20-foot high corrugated steel wall reinforced with steel “H” piles that were driven into the slope. The project failed as a result of heavy rains in December 2008 and was eventually closed in January 2009.

During the summer of 2009, the CIWMB, working with Sonoma County, provided design and construction management services to redesign and then rebuild the damaged road section using TDA as a lightweight backfill. This resulted in a smaller excavation and thus a less expensive repair. This project used approximately 330,000 waste tires and saved the county of $300,000.

Construction equipment on-site laying down TDA

TDA  placement in progress.

Pickup trucks parked on construction site of a finished road repair project.

Finished repair project.