CLEVELAND (AP) — A U.S. subsidiary of a Thailand-based company proposing to build a multibillion dollar petrochemical plant in Ohio announced Wednesday it is finalizing an agreement with a company to store liquid natural gas at an underground facility in the state, according to a statement.

PTT Global Chemical America said Mountaineer NGL Storage, a subsidiary of Energy Storage Ventures LLC, would store 1 million barrels of ethane for PTTGCA at the underground facility that will be built in eastern Ohio's Monroe County.

The $250 million storage facility is roughly 8 miles (13 kilometers) from the proposed site for for PTTGCA's petrochemical plant in Belmont County. A pipeline carrying ethane would connect the storage facility, located deep underground in salt caverns, to the proposed plant.

Petrochemical plants — like the one PTTGCA wants to build — convert ethane, a byproduct of natural gas drilling, into plastic resin used by manufacturers.

The statement said Mountaineer has all of its permits and that the project's first phase would take as many as three years to complete. The statement did not indicate when construction would begin. Ethane storage is viewed as a vital component for creating a petrochemical hub in Appalachia.

“Our storage facility will have an important role in managing the plant's supply portfolio,” said Mountaineer NGL Storage President David Hooker.

While PTTGCA has spent around $200 million on planning and engineering thus far, according to a company spokesperson, prospects for the project dimmed last week when the company's partner since 2018, a U.S. subsidiary of South Korea's Daelim Industrial Co., withdrew from the project. PTTGCA said it would be looking for other partners.

PTTGCA spokesman Dan Williamson said a final investment decision is expected sometime late this year or in the first quarter of next year.

The plant is seen as a potential economic savior for an Appalachian region that has long struggled economically from the loss of jobs in steel, aluminum and glass manufacturing decades ago. The plant would create thousands of construction jobs and hundreds of permanent positions. The hope among state and local officials is the plant will spur further development and revitalize the region.

JobsOhio, the state’s private nonprofit economic development arm, has contributed just over $70 million, including a $20 million grant in February to be paid directly to Bechtel Corp. to complete site engineering and site preparation at the site in Belmont County.