Altamont Pass

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Altamont Pass
Wind turbines at Altamont Pass
Elevation	1009 ft. / 308 m
Location	California, United States
Coordinates	37.732389° N 121.652416° W
Traversed by	I-580

Altamont Pass (el. 1009 ft. / 308 m) is a mountain pass in Northern California, United States, located in the Diablo Range between Livermore in the Livermore Valley and Tracy in the San Joaquin Valley. The pass is similar in height to Pacheco Pass to the south.

The pass carries Interstate 580, heavily congested by Central Valley suburbanization, and two railroad right-of-ways (ROWs). Only one right-of-way is still in use: the old Western Pacific ROW, now owned by Union Pacific; it is today used for the Altamont Commuter Express, with service to Pleasanton, Fremont, and San Jose. The abandoned right-of-way was used by Southern Pacific, which is now part of Union Pacific.

[edit] Wind farm

The pass is known for its wind farm, one of the earliest in the United States. The wind farm is composed of over 6000 relatively small wind turbines of various types, making it at one time the largest farm in the world in terms of capacity. Altamont Pass is still the largest concentration of wind turbines in the world, producing about 125 MW on average. They were installed after the 1970s energy crisis in response to favorable tax policies for investors.

Considered largely obsolete, these numerous small turbines are being gradually replaced with much larger and more cost-effective units. The small turbines are dangerous to various raptors that hunt California Ground Squirrels in the area. The larger units turn slower and, being elevated higher, are less hazardous to the local wildlife.

An advantage of this particular site is that under hot inland (California Central Valley) conditions a thermal low is developed that brings in cool coastal marine air through this pass, driving the turbines at a time of maximum need. Unfortunately this is not always reliable and with an inland high pressure condition the entire region can be both hot and windless. At this time additional power must be provided by natural gas powered gas turbine peaker plants.