Hyampom Road, also known as California Forest Highway 114, is located within Shasta-Trinity National Forest in northern California. It begins at California State Highway 3 (SR 3) in Hayfork, proceeds northwest and ends in the town of Hyampom at the intersection with Lower South Fork Road. The existing two-lane narrow winding roadway traverses canyon slopes with steep cuts excavated in bedrock and steep side-cast fills. The pre-construction template was comprised of a two-lane roadway with10-foot lane widths and some sections narrowing to a single lane. The roadway conditions were poor with marginally stable slopes, poor drainage, short sight distance, and other geometry issues that did not meet highway design standards. The roadway is primarily used for logging and commuter purposes and is the only year round publicly maintained access to the town of Hyampom. Multiple landslides are present along the corridor and the orientation of the bedrock structure created zones of instability. During the course of project development, the alignment was adjusted through multiple iterations to balance project cost and risk. Risk assessment included the evaluation of geological hazards, roadway safety and the achievable roadway template. Major reconstruction and rehabilitation elements of the roadway included: 1) constructing retaining walls and rock cuts, where necessary, to provide a wider roadway complete with travel lane and shoulder in each direction; thereby, reducing the severity of the existing “hairpin” curves; 2) constructing landslide mitigation systems; and, 3) providing rockfall mitigation in specific locations.
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