Southern California Edison’s Tehachapi Renewable Transmission Project (TRTP) consists of upgrading several segments of high-voltage transmission lines from 220 kV to 500 kV. TRTP includes several segments and is necessary to integrate new levels of state-mandated wind generation in compliance with California’s Renewable Portfolio Standard. Upon completion, the transmission system will be capable of delivering 4,500 megawatts at full capacity, which is enough to provide power to over three million homes. Segments 6 and 11 of this project both originate outside of Palmdale, California, run through the Angeles National Forest, over the San Gabriel Mountain Range, and into the Los Angeles area. Each segment is between 13 and 16 miles long.
Southern California Edison, Burns and McDonnell, MACTEC, Crux Subsurface, Inc., Quanta Subsurface
Crux was contracted to complete geotechnical exploration drilling for new tower sites within the Angeles National Forest. The area has always been considered environmentally sensitive, but became even more so after a September 2009 fire consumed more than ¾ of the forest. Both segments 6 and 11 extend through parts of the burned area and required special attention to preserving wildlife, minimizing vegetation disturbance and mitigating future fire potential.
The project consisted of drilling 81 geotechnical borings to obtain core samples along the proposed alignment. Helicopter-portable drills were used on a majority of the boring sites for logistical necessity and as a means of reducing environment impact. Track-mounted and heavy, four wheel drive drills were utilized in areas where the terrain was less rugged and environmental impact was less of a concern. Upon completion of the project, Crux had successfully drilled a total of 4800 feet.