The California Public Utilities Commission (CPUC) has awarded Liberty Utilities with a permit to start the first phase of the North Lake Tahoe transmission system upgrade. They also received the thumbs up to construct the second and third phases of the project, subject to verification of projected load growth.
Final phases rely on network study
In the order, the CPUC approved construction of the agency preferred alternative identified in the September 2014 final environmental impact statement for the project. The order authorized construction of the first phase which is to begin on 1 June. Liberty Utilities says that the construction of the first phase should be completed before next winter.
CPUC has ordered Liberty Utilities to carry out a new network study to verify project load growth before it starts on the second and third phases of the project. Liberty Utilities must file the study and any other information in support of its proposed construction commencement timeline for the second and third phases in advice letters for review by the CPUC Energy Division, according to the order.
If key assumptions of the study do not change after construction of the second phase, Liberty Utilities will not be required to perform a second network study for construction of the third phase.
The transmission system upgrade
The project includes the upgrade of the 60kV lines 625 and 650, and several ancillary lines of the North Lake Tahoe transmission system to 115kV, as well as the upgrade of the North Truckee, Northstar, Kings Beach, Tahoe City and Squaw Valley substations. Liberty Utilities will also decommission the Brockway substation.
The North Lake Tahoe transmission system is located within the California portion of the Lake Tahoe basin. The North Truckee and Brockway substations, as well as a small portion of line 650, are located in Nevada County, California. The remainder of the system, including line 625, is in Placer County, California.
According to the CPUC’s order, construction of the first phase would include reconductoring line 650 from Truckee to Kings Beach, California to enable operation at 120kV. For phase two, Liberty Utilities would upgrade the North Truckee, Northstar and Kings Beach substations, and decommission the Brockway substation after system demand approaches 89MW. For phase three, Liberty Utilities would rebuild line 625 from Tahoe City to Brockway Summit, California to allow operation of the entire North Lake Tahoe system at 120kV after system demand approaches 100MW. The upgrade also would enable the 60kV line 629 from Tahoe City to Squaw Valley, California to operate at its 120kV rated capacity.
Improvements to the transmission network will increase the ability to maintain the current maximum system loads during an outage on any one of the four sections of the system, and decrease reliance on the Kings Beach Diesel Generation Station. In addition, rebuilding and realigning the power lines would reduce the likelihood of outages associated with high winds, collapsed trees, snow loading, and forest fires, and would improve access to the lines for maintenance, emergency outage response, and repair activities.