Bluff Stabilization
Soil Nail Launcher, Inc.’s tools and techniques are uniquely suited for coastal and riparian zones. In extremely corrosive environments, launched fiberglass soil nails and fiberglass SuperNails® can be used. These nails can be perforated to act as drains or pressure grouted with cementicious or non-cementicious materials to improve soil properties in the nail zone. Because our work typically is conducted from above, damage to sensitive areas can be avoided, and some regulatory permits may not be required.
Once the riparian or coastal area is stabilized, a variety of surface treatments can be installed, from sculpted and stained shotcrete to bioengineered facings.
These techniques also can be applied to levees and reservoir embankments. At most sites, our access will be from above with no impact to the coastal or riparian areas. However, our highly maneuverable and lightweight equipment allows us to navigate ocean, lake, or river only access sites using a variety of amphibious craft.
Pebble Beach Drive in Crescent City, California, presented a multitude of challenges to Del Norte County Engineer, Art Reeve: Shallow landslides along the oceanfront drive were coupled with coastal erosion, confining regulations, archeological concerns, and threats of corrosion. Those challenges were particularly evident at two locations along Pebble Beach Drive.
The first, dubbed the south location, fell victim to northern California’s heavy winter rains of 2001 and 2002. A 150 linear-foot section of the 36 foot high bluff adjacent to Pebble Beach Drive had failed, leaving an over-steep head scarp. That scarp threatened the stability of Pebble Beach Drive above.
The second, dubbed the north location, consisted of six to eight feet of stiff, high-plasticity clay overlying a siltstone cliff. The clay above fell subject to surface erosion and subsequently exposed the top of the siltstone cliff below. The freshly exposed siltstone, un-capped, was then subjected to erosion and would regress at about the same rate as the clay above. This cycle repeated itself to the edge of Pebble Beach Drive.
Historically, Del Norte County would place large diameter boulders over the side of the bluff to prevent surface erosion and improve slope stability. However, local environmental groups and the California Coastal Commission no longer allow rock revetments for those types of repairs. Furthermore, at the north location, there was concern about disturbing a sacred Native American burial ground. Any drilling in or around the burial ground was strictly prohibited unless it was monitored by an archeologist familiar with the history in that area, adding costly fees to the project.
Soil Nail Launcher, Inc. was contracted to install corrosion-resistant Launched Fiberglass Soil Nails™ to stabilize the bluff and to face the bluff with shotcrete to halt surface erosion. The shotcrete was sculpted and stained to match the local geology. This solution was conducted without entering the tidal zone, thus reducing the need for certain regulatory permits. An archeologist was not required because Launched Soil Nails™ do not displace any soil material from the stabilization area. In addition, Launched Fiberglass Soil Nails™ with a sculpted shotcrete facing presented the least expensive of the potential solutions.
Contact:
Art Reeve, P.E., Del-Norte County Engineer
AReeve@co.del-norte.ca.us
James Chinchiolo, Landslide Solutions, CEO
james@landslidesolutions.com
Steve Devin, P.E., G.E., Designer of Record
sdevin@sbcglobal.net
