The mine-to-mouth examination planned under the environmental impact statement and Endangered Species Act will address the overall regional impact of the long-standing Four Corners power station and BHP Billiton’s 13,000-acre Navajo coal mine.

The mine employs mostly Navajo workers and is a two-dragline open cut producing about 8.5 million tons per annum of coal for Arizona Public Service’s 2040-megawatt Four Corners.

Both facilities are situated on the Navajo Indian reservation leased from the Navajo nation.

Four Corners, which has been operational since 1963, is commonly described as one of the most polluting in the country, with regional media outlets purporting an omnipresent haze on the San Juan river basin is due to the plant’s emissions.

Colorado’s Durango Herald even said the smoke plume from the station was visible from space during the early days of space flight.

The decision to implement an official inspection follows the opening of two pending lawsuits from Navajo activists and conservation groups regarding controversial expansion ambitions at the coal complex.

The suits filed against the federal government contend that public health and environmental risks were not taken into full consideration when BHP was approved to expand mine operations.

The conservationists and Navajo activists said the expansion approval was rushed through after a cursory environmental analysis covered only a limited area where BHP planned to expand the mine.

The upcoming federal inspection will analyse the effects of mining, coal combustion and waste disposal in a broader context, while noting the impacts associated with transmission corridors that deliver electricity to regional markets.

Four Corners provides electricity to California, Arizona, New Mexico and Texas.