Altamont Winds Inc (AWI)'s 83MW of 100kW turbines in the Altamont Pass were not brought online again after they were closed from 1 November to 15 February, a routine annual measure to protect endangered birds.

Hundreds of turbines and towers are being taken down. Foundations must also be removed, and the site must be reseeded and graded, said Sandra Rivera, assistant deputy director of planning at Alameda County, adding it would take "some time to decommission the site".

In October, AWI's vice president Bill Damon told the US Fish & Wildlife Service: "The reduction of avian impacts was a primary factor that influenced our decision to discontinue operating our Altamont wind farms." The project's permanent closure had not been confirmed until now.

The 828 Kenetech turbines dated from the 1980s and had lattice towers. For many years, bird kills has been a heated issue in the area, home to many nesting golden eagles.

An AWI affiliate, Altamont Winds LLC , has applied to repower the some site with the 54MW Summit Wind project. It was considering Suzlon's S97 2.1MW turbines.

The county approved 27 of the 33 turbine sites planned, said Rivera. Altamont Winds LLC has appealed to the Board of Supervisors seeking approval of 31 sites.

The new project could be built by year-end 2017, said Rivera. The two companies declined to comment.