Sequoia National Park, CA

Generals Highway, FHWA Central Federal Lands Highway Division and CH2M HILL

The Generals Highway was constructed from 1921 to 1926 by blasting and excavating the granite and metamorphic bedrock and creating fills adjacent to the cuts to provide the present roadway widths. The terrain throughout the site is mountainous with steep slopes on either side of the roadway. Roadway improvements were proposed to improve safety and mobility on the mountain road. The improvements included rehabilitation or new construction of CIP retaining walls, cantilevered walls, drainage structures, base material, and pavement rehabilitation. Construction costs for the roadway were exceeding the project’s budget and Yeh and Associates was asked to look at the project for possible alternate construction methods. Yeh and Associates initially performed a geologic and geotechnical site evaluation along the roadway for geologic structures, geologic and geotechnical site evaluation along the roadway for geologic structures, geologic hazards, surface and subsurface conditions, and pavement condition survey and proposed alternative alignments and construction options for the roadway.

As part of the widening, the existing historic rock parapet walls were to be moved and rebuilt. This option was being considered as it did not require additional rock cuts but did involve construction of a significant retaining wall in the downslope fill areas. Our site observations indicated that the existing retaining walls and downslope fills were moving and appeared to have been moving for some time.

Based Yeh and Associates field evaluation, suggestions were provided for selection and design of soil nail and micropile retaining walls either in conjunction with existing rock parapet walls or to support new rock parapet walls. In addition, our work indicated that several areas could be considered for rock cuts and potentially reduce construction costs. Subsequently, we were requested to perform site investigations to develop the geotechnical information to assist in the design of the alternatives proposed.

Yeh’s key personnel that worked on the project included Rick Andrew who was the project manager, Ben Arndt and Paul Macklin both were the project engineers for various portions of the work and Jon Lovekin was the project geologist.