SHN provided geologic and geotechnical services to support the Humboldt County Department of Public Works in an effort to increase curve radius and improve safety on Bald Hills Road where it descends the western valley wall of the Klamath River valley. The project consisted of investigation of nine tight switchback curves, which will be widened and will have improved grades.

Our investigation included geologic reconnaissance and subsurface investigation along the proposed new alignments utilizing machine borings, which required a special all-terrain drill rig with a portable, detachable drill mast, hand auger borings, and backhoe test pits. Laboratory testing was conducted on selected samples in our accredited Eureka Materials Testing lab to determine strength characteristics.

Based on the preliminary design provided by the County, we evaluated cut bank heights and fill prism thicknesses and provided geologic and geotechnical conclusions and recommendations. The realigned portions of the roadway will require substantially higher cuts and thicker fills than are currently associated with the existing road geometry.

We provided geotechnical recommendations for site preparation, cut bank geometry, site drainage, and suitability of on-site materials for use as fill. Geologic investigation for the project focused on assessment of existing and potential landslide hazards and determination of bedrock characteristics.

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