A 35-mile double-circuit 220-kV transmission line was installed as part of the Eldorado-Ivanpah Transmission Project to accommodate power from new solar developments. Construction in this sensitive desert landscape along the southeast California-Nevada border required meeting strict environmental mandates.
Several abrupt mountain ranges surround the desert landscapes of the Eldorado and Ivanpah valleys, where aprons of sediment slope down to scrub brush and several dry lake beds in the valley bottoms. This fragile desert habitat along the California-Nevada, U.S., border is home to several protected species such as the desert tortoise and presents numerous challenges that make it hard even to contemplate a major transmission line through this region.
However, the sun that shines in the Ivanpah Valley also is ideal for new solar generation projects, with up to 1,400 MW of solar development coming on-line over the next few years. This new solar generation will help California utilities like Southern California Edison (SCE) to meet the state’s ambitious renewables portfolio standard, which requires 33% of generation from renewable sources by 2020.
SCE’s existing transmission facilities, including a 35-mile (56-km) single-circuit 115-kV transmission line, were inadequate for this anticipated development, which is how the Eldorado-Ivanpah Transmission Project was born. The project crossed lands managed by the Bureau of Land Management, which required SCE to implement some of its most aggressive and proactive environmental and safety programs to date, encompassing environmental monitoring, training, inspection and overall agency communication. All of this was achieved under an accelerated 18-month project schedule to meet a deadline for on-line generation testing of three new solar partners’ solar-generation facilities.
The end result was a successful project that leveraged technology and teamwork to achieve project goals under a series of demanding constraints. Using a state-of-the-art Web-based platform known as POWER360 as a portal to access and integrate complex project data for quick decision making, the team was able to achieve a collaborative approach with regulatory agencies that resulted in substantially quicker response times than SCE typically has experienced, effective adjustment of plans in the field to continue construction even during heightened bird activity season, and significantly above-average safety results. Taking these results to heart, SCE plans to use similar approaches for future project development.
SCE filed an application for approval with the California Public Utilities Commission in May 2009 and an initial application with the Public Utilities Commission of Nevada in April 2010. The Eldorado-Ivanpah Transmission Project includes five major components:
- A new 220/115-kV Ivanpah substation in San Bernardino County, California, just across from Primm, Nevada
- Replacement of an existing 115-kV line with a 35-mile double-circuit 220-kV line with optical ground wire cable
- Upgrades at the Eldorado substation near Boulder City, Nevada
- Construction of two alternate telecommunications pathways as well as other equipment to connect the project to SCE’s existing telecommunications system
- Installation of a total of 211 lattice steel towers and 10 H-frame steel pole structures.
SCE hired POWER Engineers to design the new transmission line and perform owner’s engineer/construction management services. The construction contract was awarded to PAR Electrical Contractors in August 2012, and SCE received notice to proceed from the California and Nevada utility commissions the following month.
The team faced several significant challenges:
- SCE was issued a permit under the Endangered Species Act that would allow up to two incidental takes of desert tortoise, a threatened species that is concentrated in the valley. Other projects including solar plant construction had been stopped as a result of too many takes, and regulatory agencies limited SCE to no more than two takes because of concerns that previous mitigation plans had not been restrictive enough and additional construction could further harm the species.
- Any bird nest — defined as two sticks on a structure or ground — would stop all project activity within a specified buffer under California’s interpretation of the Migratory Bird Treaty Act.
- Use of helicopters to fly in preassembled lattice towers would require consideration of dust control issues and potential disruption of protected desert bighorn sheep.
- Extensive watering and dust monitoring would be required in the two states’ water-restricted areas.
- Species previously thought to be nonexistent in the area were found, including the Mojave green rattlesnake, which is considered to be the most poisonous snake in the United States, the burrowing owl and the American badger.