BISMARCK, N.D. (AP) — Standing Rock Sioux Tribe members have long maintained that a leak in the Dakota Access oil pipeline would threaten their Missouri River water supply, and on Wednesday they will argue that a new proposal to double the line’s capacity magnifies the probability of a disastrous oil spill.

Full Coverage: Dakota Access Pipeline

North Dakota regulators will hold a hearing in Linton, a town of 1,000 along the pipeline’s path. The Public Service Commission will take comments from tribe members and other pipeline opponents in the community near where a pump station would be placed to increase the line’s capacity from 600,000 barrels per day to as much as 1.1 million barrels. A barrel is 42 gallons.

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Texas-based Energy Transfer proposed expanding its pipeline in June to meet growing demand for oil shipments from North Dakota, without the need for additional pipelines or rail shipments.

The $3.8 billion pipeline was subject to prolonged protests and hundreds of arrests during its construction in North Dakota in late 2016 and early 2017 because it crosses beneath the Missouri River, just north of the Standing Rock Sioux Reservation. The tribe draws its water from the river and fears pollution. Energy Transfer insists the pipeline and its expansion are safe.

The company also plans additional pumping stations in South Dakota, Iowa and Illinois. Commissioners in a South Dakota county last month approved a conditional use permit for a pumping station needed for the expansion. Permits in the other states are pending.

The proposed expansion would “increase both the likelihood and severity of spill incidents,” the tribe said in court filings ahead of Wednesday’s hearing, which an administrative law judge will oversee.

The company said in court filings that its $40 million pump station built on a 23-acre site would produce only “minimal adverse effects on the environment and the citizens of North Dakota.”

Opponents argue North Dakota’s all-Republican, three-member Public Service Commission should consider effects all along the line and not solely at the pump station location.

Energy Transfer argues the commission must only consider a permit application for its pump site and that the tribe is attempting to “confuse issues before the commission.”

The company moved to strike testimony from three witnesses for the tribe, including a pipeline consultant who maintains that increasing pressure in a pipeline raises the risk of it failing.

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Tribal attorneys argue in court papers that the company is seeking to prevent the tribe and the public from “meaningfully participating” in the hearing.

Public Service Commission President Brian Kroshus said it is up to the administrative law judge to decide if the testimony from the tribe’s experts will be allowed. Kroshus said the commission will consider all comments from the meeting and determine “what is relevant and jurisdictional” to the panel.

The hearing comes in the wake of a 383,000-gallon (1.4 million-liter) Keystone pipeline oil spill in northeastern North Dakota. The line owned by TC Energy restarted Sunday, nearly two weeks after the spill was reported. The cause of the leak has not been disclosed.