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