PIERRE, S.D. (AP) – South Dakota residents were split Monday over the merits of allowing the Keystone XL oil pipeline through the state, with some telling regulators the project would be an economic engine but others calling it a grave threat to the environment.

More than 50 people offered their opinions on the state’s portion of the pipeline during the three-hour South Dakota Public Utilities Commission session. The commission will make its decision after holding a final evidentiary hearing starting in late July.

South Dakota is one of several fronts where TransCanada Corp. is stalled in attempting to get approval for the long-delayed oil pipeline that would cut through South Dakota and other states to move Canadian oil to the Gulf Coast.

South Dakota initially authorized the project in 2010, but regulations dictate permits must be revisited if the construction of the project doesn’t start within four years of their issuance. The Public Utilities Commission is now considering TransCanada’s guarantee that it can complete the project while meeting the conditions of the 2010 approval.

The pipeline, first proposed in 2008, still requires presidential approval because it crosses an international border. It is also wrapped up in an ongoing Nebraska court case from landowners who oppose it.

The public hearing in South Dakota isn’t a part of the official legal record of the state Public Utilities Commission’s proceedings on the permit, but Chairman Chris Nelson said the testimony would help the panel form questions during the pipeline project process.

Opponents argued the pipeline has potential to ruin ground water and exacerbate climate change. Others also said the benefits of the proposed pipeline have been overstated.

“I believe that the tar sand oil ... should remain in the ground in Canada,’’ said Hazel Bonner of Rapid City. “For myself, my children and my grandchildren, I oppose the Keystone ‘tar sands’ XL pipeline.’’

Some Native American tribes, landowners and environmental groups are actively working against the pipeline through the Public Utilities Commission process.

The pipeline would go from Canada through Montana and South Dakota to Nebraska, where it would connect with existing pipelines to carry more than 800,000 barrels of crude oil a day to refineries along the Gulf Coast. It could also transport some crude from the Bakken oil field.

Supporters said the pipeline would help create jobs and bring in needed tax revenues in South Dakota. They also said pipelines are a safer transportation method than rail service. Representatives of South Dakota Gov. Dennis Daugaard and U.S. Sen. Mike Rounds spoke in favor of the pipeline.

Tom Wilson, who lives in Buffalo, South Dakota, and owns a business that operates in Dickinson, North Dakota, will have a work camp on his property for the construction of the pipeline.

“They do hire locals. It will affect our local economy,’’ said Wilson, 62. “Aren’t we better off pulling in fuel from Canada?’’

The utilities commission plans to hold the final hearings on the issue between July 27 and August 4.