The court will hear arguments on August 31 in Topeka, Kansas, on the validity of the state permit issued in 2010 to start construction of the 895-megawatt plant near Holcomb.

Sierra Club and Earthjustice have argued Kansas’ Department of Health and Environment improperly granted regulatory approval to the project.

They said the proposed plant would prove unnecessarily damaging to the environment and on such basis they were pushing for the permit to be overturned.

Sunflower Electric Power and Colorado-based Tri-State Generation and Transmission Association maintain that the state's permit is legally valid.

The argument between opposing parties has raged on through the administrations of three Kansas governors, each one having their own opinions on the plant’s proposal.

Meanwhile, the Sunflower project has been on indefinite hold during the dispute.

In January, a federal judge further delayed the project until a federal environmental impact study could be completed.

Sunflower spokeswoman Cindy Hertel said the cooperative's management would not comment before the state Supreme Court's review.

Sunflower serves 400,000 people in Kansas but most of the new electricity would be transferred to other states.

Earthjustice attorney Amanda Goodin said the state negotiated the deal with Sunflower to break a political stalemate, which resulted in issuance of a Kansas Department of Health and Environment permit that fell short of Kansas’ obligations under the federal Clean Air Act.

Goodin, who joined Earthjustice in 2008, said KDHE failed to properly limit emissions of mercury, nitrogen oxide and sulphur dioxide and Sunflower cast aside cleaner technology for burning coal in order to cut costs.

“KDHE let Sunflower have their way,” Goodin said.

"We think it's very clear they should have done better.”