The Tehachapi Renewable Transmission Project (TRTP) consists of new and upgraded electric transmission lines and substations that are intended to bring the renewable wind power generated in the Tehachapi area to Southern California Edison's (SCE) existing electricity transmission system. Terracon was contracted to provide geotechnical services for the design and construction of Segments 1, 2, and 3 of the TRTP. Segment 1 involves the construction of approximately 25.5 miles of 500 kV transmission lines between SCE's existing Antelope and Pardee Substations. Segment 2 consists of approximately 21 miles of 500kV transmission line and 2,400 feet of 220kV transmission line. Segment 3 consists of 26.5 miles of 500 kV transmission line between the existing Antelope Substation and SCE's Substation One and 9.6 miles of 220 kV transmission line between Substation One and Substation Two. The purpose of the project was to provide geotechnical recommendations for the design of the proposed tower foundations and general earthwork recommendations related to the construction of the proposed project. During Terracon's site geologic reconnaissance, several towers proposed for the TRTP were identified within mapped and unmapped landslides. Terracon provided mitigation measures for slope instability to aid in the design of the towers. Mitigation measures included replacement and recompaction of landslide debris and/or installation of soil nails. Terracon also logged borings during the field investigation to determine approximate amounts of landslide debris. Several of the towers located with mapped/unmapped landslides were to be founded on micropiles. Terracon performed analyses on micro-pile groups and developed the geotechnical design criteria for the piles. The mountainous terrain of the San Gabriel Mountain Range and the foothills of the Tehachapi Mountains posed an interesting challenge. About 37 boring sites required the use of a helicopter to transport a drill rig to the site. Additional coordination and special attention was required to supply the sites with water for the drilling operation and the overall health and safety of the project.
Los Angeles, CA